Archive for November, 2007
Defination of GREENHOUSE.
greenhouse, enclosed glass house used for growing plants in regulated temperatures, humidity, and ventilation. A greenhouse can range from a small room carrying a few plants over the winter, to an immense heated glass building called a hothouse or conservatory, covering acres of ground and used for forcing fruits or flowers out of season. Greenhouses have long been used for holding plants over cold seasons and for growing tropical plants and less hardy fruits, but only in this century has the greenhouse been used for forcing vegetables. Now millions of dollars’ worth of plant products are raised yearly in greenhouses.
Common Nutrient Management Practices used by U.S. Farmers
A number of nutrient management practices are used to enhance fertilizer use efficiency and reduce nutrient losses into the environment. These practices include:
- Assessing nutrient need through annual or regular soil and plant tissue testing before applying nutrients, in contrast to limited or no testing before applying nutrients. Soil testing identifies the amount of nutrients already available for plant uptake, and is used to identify the additional amounts of nutrients needed to meet a realistic yield goal. A plant tissue nitrogen test uses chlorophyll (or greenness) sensing to detect nitrogen deficiency during the growing season to assist in assessing the need for additional commercial fertilizer applications. Correction of any nitrogen deficiency is then made through chemigation or other foliar application.
- Timing nutrient application to tailor feeding to plant-growth needs, for example, split application of nitrogen fertilizer into at planting and after planting, in contrast to fall and early spring applications of nitrogen before planting.
- Applying nutrients close to the root zone so they are more readily accessible to the plant, through banded and injected applications and chemigation, in contrast to ground and air broadcast and application in the furrow. With side-dressing or banded application, granule or liquid nitrogen fertilizer is placed to one side of the plant or placed every other row at planting or during the growing season.
- Selecting the nutrient product according to the chemical stability in the soil, in order to minimize nutrient loss to the environment. For example, use an ammonia-based fertilizer on fields with high leaching soils, and a nitrate-based fertilizer on fields where ammonia volatilization is a problem.
- Rotating nitrogen-using with nitrogen-fixing crops. Cover crops are planted between crop seasons to tie up and preserve nutrients, in contrast to continuous planting of the same nitrogen-using crop and not planting any cover crops.
- Applying manure and organic waste based on manure and waste test results and nutrient management plan. Adequate storage is available for manure so that applications will mesh with plant nutrient needs and applications are injected or incorporated into the soil.
- Using nitrogen inhibitors and other products to slow the release of nitrates from ammonium fertilizers until later in the growing season, by delaying the conversion of ammonium nitrogen into nitrate nitrogen, which is susceptible to leaching. N-inhibitors can also be used with manure and other forms of organic nitrogen fertilizer.
- Urease inhibitors—Chemical compounds that can be added to urea to slow the conversion of urea to ammonium and therefore to slow nitrate leaching.
- Slow-release nitrogen fertilizer—Fertilizer coated with chemicals that can retard release of nitrogen from applied fertilizer and prolong the supply of nitrogen for plant uptake.
- Refraining from broadcasting nitrogen fertilizer, or if broadcast, incorporating the product into the soil, which reduces the losses of nitrogen to the atmosphere. Certain nitrogen products, especially urea, are subject to extensive volatilization when broadcast. Certain nitrogen products are injected or knifed-in, usually 12-24 cm below the soil surface. Nitrogen can also be incorporated into the soil by tillage. High-pressure liquid nitrogen such as anhydrous ammonia is the most common form of nitrogen injected into the soil. Nitrogen solutions in low-pressure liquid form are also injected into the soil.
- Applying all nitrogen at and/or after planting, when the demand by the crop is greatest, which reduces the risk of nitrogen loss through leaching. Conversely, applying all nitrogen in the fall can increase the risk of leaching, under certain soil and weather conditions.
Results from the 1996 USDA Agricultural Resources Management Study survey of corn farmers indicate a modest utilization of nutrient testing techniques on corn acreage. Soil tests were the most extensively used (on 44 percent of the corn acreage). Nitrogen tests, nitrogen inhibitors, and broadcast applications with incorporation were used to lesser degrees. Nitrogen management on those acres receiving the nitrogen test followed recommendations closely, with 82 percent receiving nitrogen at rates exactly as recommended or lower. Nitrogen fertilizer was applied to corn several times during the year, with the largest acreage receiving it before planting of corn, either in the fall, spring, or both. The second largest bloc of acreage had nitrogen applied at or after planting time, followed by all the nitrogen applied in the fall.
Potential Contribution of Precision Agricultural Technologies Contribute to Nutrient Management
Precision agriculture is typically characterized as a suite of information technologies used to monitor and manage sub-field spatial variability. Variable rate application of seeds, fertilizers, pesticides, and irrigation water has the potential to enhance producers’ profits and reduce the risk to the environment from agricultural production through the tailoring of input use and application more closely to ideal plant growth and management needs.
Precision agriculture developments reflect innovations during the last decade in the computer, telecommunications, and satellite industries which have made more detailed spatial and temporal management of nutrients and other inputs within fields technically feasible. The application of these information technologies, known as precision farming or site-specific farming, enables producers to monitor and differentially manage small areas of a field that have similar soil or plant characteristics. Components of a comprehensive precision farming system typically include:
- Intensively testing soils or plant tissues within a field
- Equipment for locating position within a field via the Global Positioning System (GPS)
- Ayield monitor
- A computer to store and manipulate spatial data using some form of Geographic Information System (GIS) software
- A variable-rate applicator.
More involved systems may also use remote sensing from satellite, aerial, or near-ground imaging platforms during the growing season to detect and treat areas of a field that may be experiencing nutrient stress.
Precision farming has the potential to improve net farm income by: (1) identifying places in a field where additional nutrient use will increase yield, and thus farm income, by more than the added cost; and (2) identifying places where reduced input use will reduce costs while maintaining yield. One preliminary estimate of additional fixed and variable costs of precision farming for corn is about $7-$8 per acre (Lowenberg-DeBoer and Swinton, 1995). Precision farming also has the potential to reduce off-site transport of agricultural chemicals with surface runoff, subsurface drainage, and leaching (Baker and others, 1997; Watkins, Lu, and Huang, 1998). Two years of Kansas field data indicate less total nitrogen fertilizer use with precision farming than with conventional nitrogen management (Snyder and others, 1997).
Corn production represents a potentially large market for precision agriculture technologies as corn producers are the largest users of cropland and agri-chemicals in U.S. agriculture. USDA surveys in 1996 and 1997 indicate that about 10 percent of all corn farms in the United States are using some aspect of precision farming (Daberkow and McBride, 1998). Among precision agriculture adopters, 70 percent used some aspect of precision agriculture—grid soil sampling, variable-rate technology (VRT) for lime or fertilizer application, or yield monitors.
Results from 1996 USDA Agricultural Resources Management Study found precision agriculture adopters more likely than non-adopters to:
- Operate larger farms with greater assets and sales
- Farm in the central Corn Belt (IL, IN, or IA)
- Have more corn acres and achieve higher yields
- Earn greater cash farm income
- Have completed college
- Use a computerized farm record system
- Be less than 50 years of age
- Rely on crop consultants for information on precision farming
Additional information is available from precision agriculture technology web sites.
Extent of Animal Manure Use in U.S. Corn Production
Animal manure contains nutrients and organic matter that can contribute to plant growth. However, its availability and content variability often limits its use in crop production. In the case of corn, data from the 1996 ARMS survey of U.S. corn growers in the 16 major corn producing States show that 8.4 million acres, 12 percent of the corn acres, received 50 million tons of manure. The average application rate was 5.9 tons per acre.
Pennsylvania had the largest percent of corn acres treated with manure, 58 percent, followed by Minnesota and Michigan. Dairy manure was the most common source of manure, applied to 42 percent of the corn acres on which manure was applied. Next in importance were cattle manure, applied to 27 percent of corn acres receiving manure, and hog manure, applied to 23 percent of the manure-receiving corn acres. Sixteen percent of corn acres on which manure was applied were soil tested for nitrogen.
The method of spreading and incorporating (or not incorporating) manure on corn acres influences the amount of nitrogen available for the crop. Typical application methods include surface broadcast using a manure spreader, irrigation systems, a tank wagon followed by incorporation by plow or discing, or injection (knifing) under the soil surface. For the States surveyed, manure was applied in a solid form to 72 percent of the corn acreage with the remaining acreage share receiving it in liquid form. Incorporation at time of application occurred on 68 percent of the manured acres, with 32 percent not incorporated.
In general, the closer to planting time that manure is applied, the greater the availability of nutrients for plant growth. Early spring application of manure before planting, thus allowing for the mineralization of organic nitrogen, is considered the best for corn production. Fall application of manure, even with incorporation, can result in large nitrogen losses because of the time between application and the next growing season. In the surveyed States, 60 percent of the manured acres received applications in the spring before planting, and 39 percent received the manure in the fall. Fifty percent of the manured acres received one application, and the remainder received two and three applications.
For more information refer to Chapter 4.4, Agricultural Resources and Environmental Indicators.
Trends in Precision Agriculture for Major Crops
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| For more information, contact: Wen Huang or Stan Daberkow | |
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Plant production
A few cereals provide the staple food for the majority of people in the developing regions. Rice, wheat and maize supply globally more than 50 percent of human calorie requirements. Other cereal crops that figure strongly in the diet of people in particular developing regions are barley, sorghum and millet.
Roots and tubers are also important staples. They supply up to 20 percent of the calories in the diets of people in wetter tropical regions. Some are relatively drought resistant, and may therefore also be important in less humid climates. Cassava (manioc) is an example of this group of crops. Food legumes and some oilseeds supply protein to round out the diet, and vegetables and fruit are major sources of the minerals and vitamins people need for a healthy, active life.
For most developing countries, food crop production and the harvesting, storage, handling and shipping, processing, trading and marketing of foods, food products and other products from plants are the major source of both food and employment. Often agricultural crops and products earn a share of the foreign exchange used by the nation for its development. Additionally, grass and forage crops, and crop by-products yield much of the feed needed for livestock production.
On a world basis the application of science and technology has driven food production to levels unimaginable even 50 years ago. Breakthroughs in production, however, have only been realized in some crops and in some ecologies. Food shortages are still prevalent in many regions of the world. Much remains to be done to increase food production in developing countries. Cropping practices capable of sustainable production need to be elaborated, especially for fragile ecologies such as those found in tropical high rainfall zones and also in the savannah of West Africa, which could potentially become the breadbasket of the region’s densely populated countries.
Science and technology help FAO to assist its member nations to increase food production. Typical applications include the conservation, improvement and use of genetic resources; crop management and diversification; diffusion of improved varieties; adaptation of production techniques to local conditions, development of a cropping systems and low-risk technologies for rainfed agriculture; sustainable cropping systems for areas prone to environmental degradation; use of agroecological data for crop production forecasting; and networks for regional coordination, data exchange and technical cooperation. New technology is important to the growth of agriculture. FAO therefore promotes technology generation and technology transfer so that, ultimately, farmers can be more productive.
Plant genetic resources
The genetic diversity shown in the plant kingdom is indispensable for improving agricultural production. This diversity also serves as insurance, as a buffer, against harmful environmental changes. Its role in sustainable development in agriculture and forestry as well as in environmental conservation and stability cannot be over-emphasized. The conservation of genetic diversity is an investment for and moral obligation to future generations of people. Concern over the loss of plant genetic resources for agriculture has increased in recent years because the threat of destruction of natural biotypes is growing and the existing genetic diversity is being eroded. The necessary intensification of agriculture with widespread cultivation of improved varieties is thought to be one of many factors that can lead to loss of genetic diversity. To counter this threat, since 1983 FAO has been developing a global system for safeguarding and utilizing plant genetic resources. This system consists of:
- a flexible legal framework, the International Undertaking on Plant Genetic Resources,
- an intergovernmental forum, the FAO Commission on Plant Genetic Resources, and
- a financial mechanism, the International Fund for Plant Genetic Resources.
The International Undertaking, the Commission and the Fund for Plant Genetic Resources aim to ensure the conservation, sustainable use and unrestricted availability of the germplasm of useful plants and of sources of genetic diversity or special characteristics. Necessary scientific and technical activities are the description and classification of genetic material; construction, operation and maintenance of gene or seed banks; and genetic evaluation of plant material in base and working collections for use in plant breeding and in adaptation leading to introduction of improved varieties in farmers’ fields.
Many of these activities were developed and are implemented by FAO in cooperation with the International Plant Genetic Resources Institute (IPGRI), a centre of the CGIAR. FAO is establishing a worldwide information system on plant genetic resources. This will have a component to give early warning of serious threats to genetic diversity. A periodic report of the state of knowledge on plant genetic resources is to be issued. The FAO Conference has adopted a Code of Conduct for Germplasm Collection and Transfer, and a Code of Conduct on Biotechnology as it affects the conservation and use of plant genetic resources is being developed. FAO is also seeking to establish an international network of ex situ base collections.
New and improved varieties and agricultural practices
The development and use of improved varieties will continue to provide the farmer with one of the most easily adopted and cost-effective innovations. Great advances have been made in the yields of the world’s most important staple food crops, but further improvement is possible. In particular, improved varieties and other technologies are needed that fit specific production locations and socio-economic conditions more fully. Other contributions will also be important: resistance to pests and diseases, the improvement of quality, and the adaptation of the crop to more efficient production practices, such as mechanized seeding and harvesting. For small-scale farming under difficult conditions, adaptation to low input/low soil fertility levels is a core criterion for varietal development.
Crop improvement has always been central to FAO’s food security strategy for developing countries. Hybrid maize trials began in the late 1940s. In the early 1950s FAO had a major role in the creation of the International Rice Commission. The Commission’s support to a breeding programme using the variety ÒMashuriÓwith intercrossed Japonica x Indica rice led to an improved variety that is still cultivated by farmers. In 1952 wheat and barley breeding projects were launched in the Near East. The 1960s saw increasing efforts to enable the transfer of tree and other crops formerly grown on plantations to small-farm operations.
FAO, as a sponsor of the CGIAR, supports varietal improvement and other research done at the International Agricultural Research Centres on major field food crops and is constantly exploring mechanisms to assist in the transfer of new technology from these centres to national research programmes. Such activities are expanding with increase in collaborative projects, training of staff of national research institutions and support to strengthen national and local research capacity.
Many FAO projects are designed to help national researchers develop better varieties and management practices so as to overcome constraints such as pests, diseases, drought and soil acidity that limit productivity in the specific ecologies where the crops are grown. These are continuing and recurring problems that must constantly be attacked locally by better science to find and apply effective technology. FAO also assists national researchers in their efforts to verify that research findings obtained under experimental conditions can be reproduced as closely as possible on the farm, to transfer proven technology to the farmers, and to ensure that scientists have a fuller or more accurate view of the constraints faced by farmers.
In the tropics the management of crop agriculture to sustain the agroecosystem without degradation is a major need now and for the future. One way to attain sustainability is by deliberate integration of woody perennials in crop or livestock production systems in a manner that suits local conditions and is profitable for smallholders. Several FAO projects are exploring the merit of such systems in which agroforestry has a role.
Microscopically small forms of plant life can also be harnessed to improve crop management. In rice production systems, the incorporation of blue-green algae or of Azolla can provide weed control, biologically fixed nitrogen from the atmosphere, organic matter, malaria control, and livestock feed (30 percent protein). FAO is promoting applied research on Azolla technology and its use in suitable ecologies, as well as on Sesbania, a woody plant with symbiotic nitrogen fixing capacity that can serve as green manure for crop production.
Modern biotechnology offers solutions to some old problems, especially the elimination from planting material of viruses that cause extensive losses in crop production. Biotechnology may in future defend crops against insect pests, help in breeding stress-tolerant varieties, and fix hybrid vigour in crops such as maize so that millions of small farmers will one day be able to save their own hybrid-derived seed for planting.
FAO organizes workshops, study tours and regional cooperation networks through which participating scientists can share ideas on how to solve difficult research problems and can promote technical cooperation among countries and institutions concerned with the development of agriculture in the Third World.
Seeds
The farmer uses plant genetic resources by way of seeds or vegetatively propagated planting materials. Seed is the bearer of hereditary traits and therefore essential for the continuity of the species. It is often the one input which the farmer can produce on his own farm. At the same time, seed is an excellent change agent, a tool for transfer of improved technology. The availability to farmers of quality seeds of superior varieties in adequate amounts at the right time and at fair prices is one of the most important contributions to modern agriculture.
FAO provides seed samples – more than one million since 1953 – and information on seed and sources of plants to national and international research centres, scientists and field projects. The samples are used for crop introduction, evaluation and breeding. FAO assistance includes projects for the production and use of good quality seed, training and guidance in the fields of crop plant micropropagation and multiplication, quality control, processing, storage, distribution and promotion of improved seed. Field trials and demonstrations help countries to develop the necessary technical information for their proper use and specifically for identifying new or improved varieties that are adapted to local conditions. FAO has set up a computerized seed information system to promote the collection and dissemination of information on:
- variety improvement, seed quality control, seed production and distribution in about 120 countries;
- over 300 crops and their varieties of worldwide economic importance;
- seed sources – some 7,000 addresses of seed suppliers in over 160 countries;
- seed-related equipment of over 80 manufacturers.
The publication FAO Seed Review is issued at 5-year intervals. It gives information on seed-related activities in member countries.
Crop plant nutrition
Plant growth is made possible by energy and materials for photosynthesis. Soil serves both as a structural support and as the source of the moisture and nutrients that are absorbed through the plant roots. Proper plant nutrition depends on the availability of nutrients at the right time, in suitable quantity and in the needed form and balance.
Nutrients needed by virtually all crop plants are nitrogen (N), required in the greatest amount, and lesser amounts of phosphorus (P) and potassium (K). These elements are present in all soils in varying amounts. Good agricultural practices aim to compensate for deficits which arise from many causes, including continuous crop production without restoration of the nutrients removed in plant growth.
A good, well-nourished plant cover (leaves) with active photosynthesis and a well-developed root system help to maintain the proportion of oxygen in the atmosphere, use carbon dioxide in photosynthesis, reduce the risk of erosion, minimize surface run-off of water and reduce downward leaching of nutrients. Good plant nutrition, by stimulating plant growth, also increases the humus content of soil via an enlarged root system and increased litter fall.
Increasing use of marginal land and the pressure to extend cultivation to unsuitable areas such as shallow soils and steep slopes, together with inappropriate land use practices, has led to soil degradation, nutrient ÒminingÓand declines in crop yields. Studies on larger-scale intensive cereal production have shown that an average yielding grain crop removes some 100-150 kilograms of major nutrients per hectare per year, and a 5-6 t/ha crop of rice or wheat removes up to 360 kg/ha. In addition, secondary nutrients, such as sulphur and micro-nutrients, only traces of which are required, are also lost.
Where supply of fuelwood is inadequate, animal manure is often used as fuel by small-scale farmers together with crop residues. By not returning organic material to the land, the soil’s fertility and water-holding capacity decline, increasing the vulnerability of crops to drought and reducing the productivity of soil, crops, labour and energy.
Restoring soil fertility
In areas where shifting cultivation based on Òslash and burnÓis still practised and land can not be left fallow for long after cultivation, soil fertility is lost and must be made good. Loss of fertility also occurs wherever crops are produced continuously on the same piece of land, no matter how fertile the soil may be initially. Once soils are on the verge of degradation, crop production technologies that use minimum inputs are unlikely to prevent further degradation. Restoration of soil structure and fertility will require application of mineral fertilizers and/or large dressings of manure of plant or animal origin.
Thus sustained and ecologically sound farming will depend largely on the external provision of plant nutrients. Green manure from plants, animal manure and biological nitrogen fixation all have an important contribution to make, with mineral fertilizer covering the remaining deficit.
The use of mineral fertilizers in developing countries is limited by cost and availability to the farmer. These depend on local production capacity, availability on the international market, having the foreign exchange to purchase them, and subsequently on efficient distribution and marketing systems within the country. These systems, in turn, depend on adequate infrastructure such as roads, vehicles and warehouses, as well as on an adequately trained workforce. Current fertilizer production, consumption, trade and price data are published annually in the FAO Fertilizer Yearbook.
FAO activities in plant production
Plant nutrition
FAO’s activities to improve crop plant nutrition started in the late 1950s with a call for increased use of fertilizers by Third World farmers. A Fertilizer Industry Advisory Panel, and later an FAO Fertilizer Industry Advisory Committee of Experts (FIAC) worked with FAO to improve fertilizer quality and give guidance on formulations and modes of application appropriate for different soils and climatic zones. An International Fertilizer Supply Scheme was created by FAO in 1974 at a time of severe shortages of fertilizer in developing countries. Using resources contributed by donors in cash and kind, the scheme has provided assistance to more than 60 developing countries.
To promote technology for sound use of fertilizer on small farms, FAO has assisted developing countries in: (i) conducting trials on farmers’ fields including testing of local resources like rock phosphates; tailoring fertilizer recommendations for specific localities; (ii) making plot and block demonstrations on farmers’ fields; (iii) training national research and extension staff; and (iv) improving the distribution, pricing and related policies of fertilizer and other inputs. Information from over 80,000 field demonstrations and trials in Africa, Asia and Latin America is held in a readily accessed data bank.
Efficient use of fertilizers requires often the incorporation in the formulation of secondary nutrients such as sulphur and micro-nutrients such as boron. FAO organized trials in countries of Asia and Africa have demonstrated spectacular crop responses to the application of secondary and trace micro-nutrients when included in balanced applications with major nutrients.
To support sustainable crop production that makes use of all available plant nutrients, FAO in recent years has elaborated an integrated plant nutrition system (IPNS) approach that is environmentally sound and socially and economically viable. The cropping system rather than an individual crop is the focus of attention in this approach. In addition to mineral fertilizers it envisages the use of locally available materials of plant or animal origin such as by-products of agricultural activities or, where such materials are not abundantly available, in situ production of green manures.
Alternative sources of organic materials which have considerable potential as plant nutrients for use in IPN systems are: quick growing leguminous shrubs grown as a part of the cropping system and incorporated into the soil as green manure; leguminous trees or shrubs grown in alley formation, their loppings being used as mulch materials or incorporated into the soil; nitrogen-fixing Azolla and blue-green algae; and forage legumes or food legumes, properly inoculated with nitrogen-fixing rhizobia, grown in rotations. To foster the development of biological nitrogen fixation, FAO assists in selecting the best available strains of Rhizobium and in arranging for supply of small-scale production units for their local production.
Field food crops
Research on most cereals of importance in agriculture continues at the international centres of the CGIAR and elsewhere. FAO activities focus on assessing available production technologies and on the transfer and local adaptation of proven technologies. For example, new hybrid rice technology appears to have exciting promise for hybrid seed production in countries where labour costs are low. The hybrids outyield other rices by 15 to 20 percent. FAO already has projects in several countries in Asia.
The use of improved plant varieties and production practices is still very limited in most African countries. In cooperation with national institutions FAO is using on-farm demonstrations to show farmers some of the possibilities to improve production. Among the improvements are suitable growing areas for different cereal crops, appropriate agronomic practices, and identification and field introduction of improved varieties. Special emphasis is given to demonstration of improvements in growing food legumes.
Compared with other field crops, yields of food legumes are frequently low in most developing countries. This is due to the limited introduction of improved varieties and the inadequate use of production inputs. Increased research on food legumes is needed to obtain improved technologies, as these crops have important roles in human nutrition and in the sustainability of agricultural production.
For some field food crops, such as perishable roots and tubers, increased production should be linked to increased capacity for postharvest processing and handling. Similarly, the potential of tropical soybeans as a protein and vegetable oil source can be best realized by coupling to village-level processing. FAO is developing projects that integrate processing, especially at rural level, with improved production techniques.
Root and tuber crops can be improved through the use of tissue culture techniques. The aim is to increase the genetic variation available for breeding work and to free germplasm and planting materials from virus infections which are extremely difficult to remove by other means. In collaboration with international research centres FAO promotes application of these techniques and of such other developments as the novel practice for production of some crops (e.g. potato, cassava) from true seed.
Other crops
Tissue culture techniques have also been used to good effect for the improvement of so-called industrial crops grown for fibre (cotton), edible oil (oilpalm), beverages (coffee, tea), sweetening (sugarcane), flavouring (spices) and medicinal use, and also for vegetables. For example, the use of tissue culture in sugarcane promises to almost double the sucrose content of the plant, thus releasing areas planted to this crop for production of other needed crops.
Tree crops, often grown in plantations, are sources of foreign exchange earnings for many developing countries. Such crops, and also spices, are important for smallholders as a source of income and to reduce risk through diversification of the farming system. FAO promotes science-based technology that allows more of the value added in the processing of such crops to remain in the rural areas. Equipment and techniques are adapted and demonstrated for village-level use, e.g. pressing of oilpalm kernels, extraction of essential oils from spices, and processing of a number of locally important tree crops.
FAO assists developing countries in the development of horticulture programmes aimed at supporting small farmers and rural communities. Such programmes have a wide range of objectives: to increase food security, improve consumption and nutrition, intensify production, improve income-earning capacity, and create opportunities for employment in production, processing and marketing of vegetables and fruit. Protected cultivation (greenhouse production of higher-value crops) offers considerable possibilities to improve productivity and quality and make better use of limited soil and water resources. The use of appropriate covering materials, climate control measures and integrated pest management (IPM) can increase yields substantially and provide better quality produce with low pesticide residues.
Most of the ruminant livestock production in the developing world has pastures, crop residues and fodder as its feed base. Ruminants are especially important in smallholder agriculture. Natural grazing lands still provide most of the feed used by ruminants. The availability of these lands is decreasing and their maintenance in a productive condition is often difficult or neglected because complex social issues of land tenure and grazing rights are involved.
FAO promotes recognition of the importance of grazing lands among the natural resources of developing countries. Such lands, which cover large areas of the earth’s surface, have environmental value for all people as watersheds, wildlife habitats and recreational areas, and as a means for in situ conservation of genetic resources. These valuable uses should be taken into account in land-use policies and plans, and in the design of range management systems.
The development of grazing management systems suitable for the traditional livestock sector is a major preoccupation of FAO. Grazing does not always supply sufficient feed for sustained livestock growth. The cultivation of supplementary fodder is then necessary. In arid and semi-arid areas, fodder shrubs and trees (acacia) are frequently planted because of their better dry-season productivity and resilience in drought years. In very humid areas, grass production can be problematic and shrubs (Leucaena) are useful. FAO has advised and assisted with the selection of fodder species suiting particular ecological conditions.
The productivity of both the pasture and the animal is dependent on the available nitrogen supply. Where fertilizer nitrogen is expensive or unavailable in developing countries, the cultivation of legumes as a means of fixing atmospheric nitrogen symbiotically has long been encouraged by FAO. Providing facilities for production of nitrogen-fixing Rhizobium inoculant is part of this effort. FAO also promotes use of crop residues and by-products to supplement and diversify the feedstuff base.
Fertilizers
Fertilizers are used to add plant nutrients not adequately supplied by the soil. A soil test is used to determine the amount of nutrients in the soil. The soil test report will make recommendations for the amount and type of fertilizer and/or lime you need to add to the soil for optimum plant growth. For information on soil testing refer to HGIC 1652.
NUTRIENT NEEDS OF PLANTS
There are 16 nutrient elements that are essential for the growth and reproduction of plants. Plants obtain the three most abundant nutrients – carbon, hydrogen and oxygen – from water and the air. The other 13 elements are divided into three categories: primary, secondary and micronutrients. Nitrogen (N), phosphorus (P) and potassium (K) are primary nutrients which are needed in fairly large quantities compared to the other nutrients. Calcium (Ca), magnesium (Mg) and sulfur (S) are secondary nutrients which are required by the plant in lesser quantities but are no less essential for good plant growth than the primary nutrients. Zinc (Zn), manganese (Mn), iron (Fe), boron (B), copper (Cu), molybdenum (Mo) and chlorine (Cl) are micro- nutrients which are required by plants in very small amounts.
FERTILIZER TYPES
Fertilizers may be divided into two broad groups: organic and inorganic, or chemical. An organic fertilizer is derived from a living plant or animal source. Chemical fertilizers are usually manufactured and have the advantage of low cost. The commonly used synthetic fertilizers consist almost entirely of nitrogen, potassium and phosphorus in forms that are readily utilized by plants. In contrast, the organic fertilizers are more likely to have significant amounts of micronutrients, and the macronutrients are likely to be in forms that are not as readily absorbed. Nitrogen in an organic fertilizer is slow in becoming available for plant use because the organic nitrogen must be reduced by micro-organisms to ammonium (NH4) and nitrate (NO3). Thus, the inorganic fertilizers are “fast,” while the organic fertilizers tend to be more “time- release.” A potential drawback of organic fertilizers is that they may not release enough of their principal nutrient at a time to give the plant what it needs for best growth. Because organic fertilizers depend on soil organisms to break them down to release nutrients, most of them are effective only when soil is moist and the soil temperature is warm enough for the soil organisms to be active. Microbial activity is also influenced by soil pH and aeration.
The use of organic fertilizers increases the soil’s organic matter content and improves the soil’s physical structure.
Inorganic fertilizers can be one of the major sources of groundwater pollution. The nitrogen is in such a soluble form that it tends to leach from the point of application. Water-soluble chemical fertilizers will injure plants if not washed or brushed off the foliage. Slow-release fertilizers are less susceptible to leaching and are preferred on sandy soil types, which tend to leach.
Inorganic Fertilizers: Various salts and minerals can serve as fertilizer materials. Examples are ammonium sulfate, potassium nitrate, super- phosphate, potassium chloride and potassium sulfate.
Synthetic Organic Fertilizers: These are human-made organic materials used for fertilization. Examples are urea and ureaform.
Natural Organic Fertilizers:
- Cottonseed meal is a by-product of cotton manufacturing. Formulas vary slightly but generally contain 7% nitrogen, 3% phosphorus and 2% potash. Cottonseed meal is frequently used for fertilizing acid-loving plants, such as azaleas, camellias and rhododendrons.
- Blood meal is dried, powdered blood collected from cattle slaughterhouses. It is a rich source of nitrogen, and it supplies some of the essential micronutrients, including iron.
- Fish emulsion, a well-rounded fertilizer, is a partially decomposed blend of pulverized fish. The odor is intense but it dissipates within a day or two.
- Manure is a complete fertilizer, but low in the amounts of nutrients it can supply. Manures are best used as soil conditioners instead of nutrient suppliers.
- Sewage sludge is a recycled product of municipal sewage treatment plants. Two forms are commonly available, activated and composted. Activated sludge has higher concentrations of nutrients than composted sludge and is usually sold in a dry, granular form for use as a general purpose, long-lasting fertilizer. There is some question about the long-term effect of using sewage sludge products in the garden, particularly around edible crops. Heavy metals, such as cadmium, are sometimes present in sludge, and may build up in the soil. Sludge use should be guided by results of chemical analyses of the sludge in question.
ANALYSIS OR FERTILIZER GRADE
All fertilizers are labeled with three numbers that indicate the guaranteed analysis, or the fertilizer grade. These three numbers give the percentage by weight of nitrogen (N), phosphate (P2O5) and potash (K2O). Often, to simplify matters, these numbers are said to represent nitrogen, phosphorus and potassium, or N-P-K. Remember that it is not N-P-K, but N-P2O5-K2O. For example, in a 100 pound bag of fertilizer labeled 10-10-10, there are 10 pounds of N, 10 pounds of P2O5, and 10 pounds of K2O.
Fertilizer Ratio: The ratio describes the relative proportions of N, P2O5, and K2O in a fertilizer. For example, the ration of 16-4-8 fertilizer is 4:1:2 or 4 parts nitrogen to 1 part phosphorus to 2 parts potassium.
To choose a fertilizer formulation, follow the recommendations in the soil test report.
Complete Fertilizer: A fertilizer is called “complete” when it contains each of the major plant nutrients: nitrogen, phosphorus and potassium. If plants need only one of these nutrients as indicated by the soil test report, a complete fertilizer is not called for.
Balanced Fertilizer: A fertilizer is called “balanced” only because it contains equal amounts of N, P2O5 and K2O. A 10-10-10 fertilizer is a balanced fertilizer.
Fertilizer Label: The law requires that the manufacturer guarantees what is claimed on the label. In some cases a fertilizer will contain secondary nutrients or micronutrients not listed on the label because the manufacturer does not want to guarantee the exact amounts. The gardener can rest assured that nutrients listed on the label are contained in the fertilizer.
Special-purpose Fertilizers: There are fertilizers packaged for certain uses or types of plants such as “Camellia Food,” “Rhododendron and Azalea Food.” These fertilizers belong to the “acid plant foods.” Some of the compounds in these fertilizers have an acidifying reaction so they are beneficial to acid-loving plants growing in soil that is naturally neutral or alkaline.
Slow-release Fertilizers: Slow-release fertilizers contain one or more essential elements. These elements are released or made available to the plant over an extended period. This is done in three different ways:
- Material dissolves slowly, such as granite meal and rock phosphate;
- Use of materials from which nitrogen is released by microorganisms;
- Granular material is coated with resin or sulfur, which controls the rate of nutrient release from the granules in the soil.
Slow-release fertilizers need not be applied as frequently as other fertilizers. Plants may use the nitrogen in slow-release fertilizers more efficiently than in other forms. Caution should be used in applying slow-release fertilizers around trees and shrubs because they may keep the plant growing late in the summer. Late-season growth may not harden off completely and excessive winter damage may occur.
Fertilizer/Pesticide Combinations: The major reason for buying a fertilizer combined with a pesticide is convenience. The problem is that the timing for a fertilizer application often does not coincide with the appearance of a disease or an insect problem.
Fertilizer-herbicide combinations are available for both pre-emergence crabgrass control and broadleaf weed control on lawn areas.
Fertilizer Formulation: Fertilizers come in many shapes and sizes. The type or form the fertilizer comes in is called the formulation. Some of the formulations available to the homeowner include water-soluble powders, slow-release pellets, slow-release spikes, liquids, tablets and granular solids.
APPLYING FERTILIZERS
Timing of Applications: Soil type dictates the frequency of fertilizer application. Sandy soils require more frequent applications of nitrogen and other nutrients than clay-type soils. Other factors affecting frequency of application include the plants being grown, the frequency and amount of irrigation, the type of fertilizer applied and its release rate.
Root crops require less nitrogen fertilization than leafy crops. Corn is a heavy nitrogen-feeder, while most trees and shrubs perform nicely with one good application every year.
It is important to group plants with similar fertilizer needs close together to avoid improper rates of application.
In the landscape, plants should be fertilized in late winter or spring.
Late fertilization (after July 1) of trees and shrubs can cause new flushes of growth on woody tissue that are normally adjusting themselves for the coming winter. This may delay dormancy of woody plants and cause severe winter dieback in new growth.
If you anticipate major insect damage (perhaps a hatch of grasshoppers), decrease fertilization. Tender plant tissues are more subject to damage than tissues that grew more slowly.
Application Methods: Methods of applying fertilizer depend on the formulation and the plant’s need.
Broadcasting: A recommended rate of fertilizer is spread over the growing area and left to filter into the soil or is incorporated into the soil with a rototiller or spade.
Banding: Narrow bands of fertilizer are applied in furrows several inches to the side and below the seeds or plants to be planted. Putting the fertilizer bands too close to seeds will burn seedling roots. Banding is one way to satisfy the phosphorus needs of many plants as the first roots develop. When fertilizers are broadcast and worked into the soil, much of the phosphorus is locked up by the soil and is not immediately available to the plant. By concentrating the phosphorus near the roots, the plant is given what it needs even though much of the phosphorus stays locked up.
Starter solutions: One can also use a liquid fertilizer high in phosphorus as a starter solution when setting out transplants.
Sidedressing: Dry fertilizer is applied as a sidedressing after plants are up and growing. Scatter fertilizer 4 to 6 inches from the plants. Work it into the soil and water thoroughly.
Foliar feeding: Soluble fertilizers are becoming popular for foliar fertilization. They are usually applied diluted in large quantities of water, using a hose-end sprayer or proportioning device. Foliar feeding is used when:
- Insufficient fertilizer was applied before planting;
- A quick growth response is desired;
- Micronutrients (such as iron and zinc) are locked in the soil;
- The soil is too cold for plants to extract or use the fertilizer applied to the soil.
Foliar-applied nutrients are absorbed and used by the plant quite rapidly. While this method can give relief from nutrient deficiency symptoms, it is temporary relief at best, only affecting the existing leaves and only giving good results if applied in the spring. Foliar application does not address the underlying cause of the deficiency, which is generally an imbalance of the soil pH value or nutrient availability.
WHAT’S A GOOD FERTILIZER TO BUY?
When shopping for a good fertilizer, look for a few key things:
Nitrogen Sources: For quick results, look for a fertilizer that contains the majority of the nitrogen in the nitrate, ammoniacal and/or urea forms. For long-lasting results with a low potential of leaching, shop for a high percentage of water-insoluble nitrogen, which will be more expensive than the readily soluble forms. The best buy for routine garden maintenance is a combination of fast- and slow-release nitrogen.
Get the most for your money: If there are two or more fertilizers that fit your needs, but the prices vary, calculate the actual cost per pound of plant nutrients. One way of comparison shopping for fertilizer is to compare the cost per pound of primary nutrients in the various products. Add the nitrogen, phosphorus and potassium percentages; multiply by the net weight of the package to approximate the pounds of nutrients contained. Then divide the cost of the package by the pounds of N+P2O5+K2O in the package to obtain the per-pound cost. For example, a 50 pound bag of 20-3-7 fertilizer would contain 15 pounds of nutrients (that is, 20% N + 3% P2O5 + 7% K2O = 30% of 50 pounds). If the bag of fertilizer costs $6.00, the average cost of the nutrients would be $0.40 per pound ($6.00 per 15 pounds).
A higher analysis fertilizer such as 16-4-8 will probably cost more but will cover more area than a lower analysis.
Just because a fertilizer is labeled as a lawn fertilizer (or tomato or camellia or whatever) doesn’t mean it can not be used on everything in your yard if it meets the nutritional requirements of the other plants. The exception of course is if a fertilizer also contains a weed killer or insecticide, which might injure certain plants. Don’t buy six different fertilizers if one will fit the bill.
Excerpted from the South Carolina Master Gardener Training Manual, EC 678.
Prepared by Marjan Kluepfel, HGIC Information Specialist, and Bob Lippert, Extension Soil Fertility Specialist, Clemson University.
This information is supplied with the understanding that no discrimination is intended and no endorsement by the Clemson University Cooperative Extension Service is implied. All recommendations are for South Carolina conditions and may not apply to other areas. Use pesticides only according to the directions on the label. All recommendations for pesticide use are for South Carolina only and were legal at the time of publication, but the status of registration and use patterns are subject to change by action of state and federal regulatory agencies. Follow all directions, precautions and restrictions that are listed. (New 6/99).
Changing the pH of Your Soil
The soil pH value is a measure of soil acidity or alkalinity. Soil pH directly affects nutrient availability. The pH scale ranges from 0 to 14, with 7 as neutral. Numbers less than 7 indicate acidity while numbers greater than 7 indicate alkalinity.
The pH value of soil is one of a number of environmental conditions that affects the quality of plant growth. The soil pH value directly affects nutrient availability. Plants thrive best in different soil pH ranges. Azaleas, rhododendrons, blueberries and conifers thrive best in acid soils (pH 5.0 to 5.5). Vegetables, grasses and most ornamentals do best in slightly acidic soils (pH 5.8 to 6.5). Soil pH values above or below these ranges may result in less vigorous growth and nutrient deficiencies.
Nutrients for healthy plant growth are divided into three categories: primary, secondary and micronutrients. Nitrogen (N), phosphorus (P) and potassium (K) are primary nutrients which are needed in fairly large quantities compared to the other plant nutrients. Calcium (Ca), magnesium (Mg) and sulfur (S) are secondary nutrients which are required by the plant in lesser quantities but are no less essential for good plant growth than the primary nutrients. Zinc (Zn) and manganese (Mn) are micronutrients, which are required by the plant in very small amounts. Most secondary and micronutrient deficiencies are easily corrected by keeping the soil at the optimum pH value.
The major impact that extremes in pH have on plant growth is related to the availability of plant nutrients or the soil concentration of plant-toxic minerals. In highly acid soils, aluminum and manganese can become more available and more toxic to the plant. Also at low pH values, calcium, phosphorus and magnesium are less available to the plant. At pH values of 6.5 and above, phosphorus and most of the micronutrients become less available.
FACTORS AFFECTING SOIL pH
The pH value of a soil is influenced by the kinds of parent materials from which the soil was formed. Soils developed from basic rocks generally have higher pH values than those formed from acid rocks.
Rainfall also affects soil pH. Water passing through the soil leaches basic nutrients such as calcium and magnesium from the soil. They are replaced by acidic elements such as aluminum and iron. For this reason, soils formed under high rainfall conditions are more acidic than those formed under arid (dry) conditions.
Application of fertilizers containing ammonium or urea speeds up the rate at which acidity develops. The decomposition of organic matter also adds to soil acidity.
INCREASING THE SOIL pH
To make soils less acidic, the common practice is to apply a material that contains some form of lime. Ground agricultural limestone is most frequently used. The finer the limestone particles, the more rapidly it becomes effective. Different soils will require a different amount of lime to adjust the soil pH value. The texture of the soil, organic matter content and the plants to be grown are all factors to consider in adjusting the pH value. For example, soils low in clay require less lime than soils high in clay to make the same pH change.
Selecting a Liming Material: Homeowners can choose from four types of ground limestone products: pulverized, granular, pelletized and hydrated. Pulverized lime is finely ground. Granular and pelletized lime are less likely to clog when spread with a fertilizer spreader over turf areas. The finer the grind of the limestone the faster it will change the soil pH value. Hydrated lime should be used with caution since it has a greater ability to neutralize soil acidity than regular limestone.
Time of Application and Lime Placement: Lime needs should be determined by a soil test. For more information on soil testing, refer to HGIC 1652. Soil samples should be taken in the fall for the succeeding year’s garden. If test results indicate a need for limestone, it can be applied in the fall or winter months. Generally, for best results, limestone should be applied two to three months prior to planting to allow time for it to neutralize the acidity.
The most important factor determining the effectiveness of lime is placement. Maximum contact of lime with the soil is essential. Most liming materials are only slightly soluble in water, so incorporation in the soil is a must for lime reaction. Even when properly mixed with the soil, lime will have little effect on pH if the soil is dry. Moisture is essential for the lime-soil reaction to occur. In the case of lawns, it can only be surface applied and watered into the soil.
Wood Ashes: Wood ashes can be used to raise the soil pH. They contain small amounts of potassium, phosphate, boron and other elements. They are not as effective as limestone but with repeated use, they can drastically raise the pH value of a soil, especially if the soil is sandy in texture. Ashes should not come in contact with germinating seedlings or plant roots as they may cause damage. Spread a thin layer during the winter and incorporate into the soil in the spring. Check the soil pH annually especially if you use wood ashes. Avoid using large amounts of wood ashes because excessively high pH values and subsequent nutrient deficiencies may result. Coal ashes do not have any lime value and may actually be acidic dependent on the source.
DECREASING THE SOIL pH
Many ornamental plants and some fruit plants such as blueberries require slightly to strongly acid soil. These species develop iron chlorosis when grown in soils in the alkaline range. Iron chlorosis is often confused with nitrogen deficiency because the symptoms (a definite yellowing of the leaves) are similar. Iron chlorosis can be corrected by reducing the soil pH value.
Two materials commonly used for lowering the soil pH are aluminum sulfate and sulfur. These can be found at a garden supply center. Aluminum sulfate will change the soil pH instantly because the aluminum produces the acidity as soon as it dissolves in the soil. Sulfur, however, requires some time for the conversion to sulfuric acid with the aid of soil bacteria. The conversion rate of the sulfur is dependent on the fineness of the sulfur, the amount of soil moisture, soil temperature and the presence of the bacteria. Depending on these factors, the conversion rate of sulfur may be very slow and take several months if the conditions are not ideal. For this reason, most people use the aluminum sulfate.
Both materials should be worked into the soil after application to be most effective. If these materials are in contact with plant leaves as when applied to a lawn, they should be washed off the leaves immediately after application or a damaging leaf burn may result. Take extreme care not to over-apply the aluminum sulfate or the sulfur.
You can use the following tables to calculate the application rates for both the aluminum sulfate and the sulfur. The rates are in pounds per 10 square feet for a loamy soil. Reduce the rate by one-third for sandy soils and increase by one-half for clays.
| Pounds of Aluminum Sulfate to Lower the pH | |||||
| Present pH | Desired pH | ||||
| 6.5 | 6.0 | 5.5 | 5.0 | 4.5 | |
| 8.0 | 1.8 | 2.4 | 3.3 | 4.2 | 4.8 |
| 7.5 | 1.2 | 2.1 | 2.7 | 3.6 | 4.2 |
| 7.0 | 0.6 | 1.2 | 2.1 | 3.0 | 3.6 |
| 6.5 | 0.6 | 1.5 | 2.4 | 2.7 | |
| 6.0 | 0.6 | 1.5 | 2.1 | ||
| Pounds of Sulfur to Lower the Soil pH | |||||
| Present pH | Desired pH | ||||
| 6.5 | 6.0 | 5.5 | 5.0 | 4.5 | |
| 8.0 | 0.3 | 0.4 | 0.5 | 0.6 | 0.7 |
| 7.5 | 0.2 | 0.3 | 0.4 | 0.5 | 0.6 |
| 7.0 | 0.1 | 0.2 | 0.3 | 0.4 | 0.5 |
| 6.5 | 0.1 | 0.2 | 0.3 | 0.4 | |
| 6.0 | 0.1 | 0.2 | 0.3 | ||
Prepared by Marjan Kluepfel, HGIC Information Specialist, and Bob Lippert, Extension Soil Fertility Specialist, Clemson University.
This information is supplied with the understanding that no discrimination is intended and no endorsement by the Clemson University Cooperative Extension Service is implied. All recommendations are for South Carolina conditions and may not apply to other areas. Use pesticides only according to the directions on the label. All recommendations for pesticide use are for South Carolina only and were legal at the time of publication, but the status of registration and use patterns are subject to change by action of state and federal regulatory agencies. Follow all directions, precautions and restrictions that are listed. (New 6/99).
Indoor Plants – Cleaning, Fertilizing, Containers and Light Requirements
Indoor plants are widely used in homes and commercial buildings such as offices, restaurants and shopping malls. They help us stay in touch with nature and, in a sense, “bring the outside indoors.”
CLEANING
Indoor plants may collect dust or greasy films that dull their appearance, making them less attractive. Clean leaves are favorable to healthy growth. Also, cleaning helps control insects and enhances the plants’ attractive-ness. Products that clean and shine leaves are generally not recommended because the waxy coating residue may interfere with air exchange. Never use these products on plants that have hairy leaves, such as African violets.The best way to clean leaves that are not hairy is to dampen a soft cloth with water and wipe the lower and upper surfaces of each leaf. An alternative is to place the entire plant outdoors or in the shower to rinse it off. Plants with hairy leaves should not be dusted with a wet cloth but with a soft cosmetic brush. A pressure sprayer may be employed.
FERTILIZING
All plants require certain essential elements for proper growth. Indoor plants, in low light conditions of the interior environment, have reduced fertilizer requirements.Observation will guide you in determining a plant’s fertilizer needs. As a rule, applications should be more frequent when the plants are in their growth stage(s). This is usually in the spring and summer when sunlight intensities increase and the days are warmer and longer. During the short days of winter, many indoor plants
that receive little or no artificial light enter a “resting stage.” If plants go into a winter rest period, do not give them fertilizer. Frequency of fertilizer application varies somewhat with the vigor of growth and age of each plant. Rapid, new growth is often undesirable, as plants may outgrow their locations. As a rule, fertilizer applications should be more frequent when the plants are growing. Fertilize at the recommended label rate every two or three months, or dilute the fertilizer to about one-tenth the recommended rate and use this solution at every watering during the growing season. An alternative to these methods is to fertilize every seventh watering.A complete fertilizer (one that contains nitrogen, phosphorous and potassium) is an excellent choice for indoor gardens. Choose a balanced fertilizer for foliage plants, such as 20-20-20, and one that is higher in phosphorous for flowering plants, such as 15-30-15. These numbers represent the percents by weight of nitrogen, phosphorus and potassium in the fertilizer.
Fertilizers are available for indoor plants in liquid form, water-soluble granules and slow-release forms (granules, stick or tablets). Water-soluble fertilizers are often preferred because dilute solutions reduce the potential for fertilizer burn.
Soils that have a white film on the surface or pots with a white crust on the rim or drainage hole may indicate that the plant is being overfertilized and/or possibly overwatered. Salt buildup in the soil can lead to root damage, causing symptoms such as reduced growth, brown leaf tips, dropping of lower leaves and wilting of the plant.
The most effective way to prevent soluble salt injury is to prevent the salts from building up. Water correctly by watering the soil thoroughly and allowing the excess to flow out of the drain holes into a tray which is emptied.
INDOOR CONTAINERS
Many types of containers can be used for growing plants. Most pots with bottom drainage holes are made of plastic, ceramic or clay, whereas decorative containers without drainage holes may be made of clay, ceramic, plastic, wood, copper, brass and various other materials.It is important to choose the correct size container for the plant. Containers too small or too large present an unbalanced appearance. An appropriate container should provide room for soil and roots, allow sufficient headroom for proper watering, and be attractive without competing with the plant.
Two methods for potting indoor plants are: (1) planting directly in the container and (2) placing a potted plant in another, more decorative container (“double-potting”). When plants are potted directly in the container, the container should have a drainage hole and a tray to catch the excess water. If the pot does not have a drainage hole, place a layer of coarse gravel in the bottom to allow a space for excess water (it is important not to saturate soil in such containers). The “double-potting” technique can be used with decorative containers with or without drainage holes. The smaller, interior pot should have a drainage hole. If the decorative pot does not have a drainage hole, place a layer of gravel in this pot, and place the potted plant on the gravel layer. No gravel layer is necessary if the decorative pot has a drainage hole. Be sure to place a tray beneath the pot to catch the excess water. Never place pots directly in contact with the carpet, floor or furniture as moisture can damage its surroundings. Clay pots are porous and allow air movement through the sides of the pot. This allows the soil to dry and oxygen to reach the roots. Nonporous containers prevent water from evaporating through the sides, thus, plants require less frequent watering than those in clay pots.
LIGHT REQUIREMENTS
The environment in our homes dictates which plants will grow vigorously and which will suffer. The most important environmental factor in growing plants indoors is adequate light. Light provides the energy source needed for plants to manufacture food. The amount of light is commonly measured in foot-candles (ft-c). The interior of a well-lighted home is often less than 100 ft-c, while outdoor light intensity on a clear sunny day may exceed 10,000 ft-c. Plants differ greatly in their light intensity requirements (see table). Indoor plants are often classified by the amount of light necessary for growth:
About 100 ft-c for 12 hours per day are necessary simply to maintain plant quality for one year, and at least 200
ft-c for 12 hours per day are necessary for foliage plants to manifest any benefit from fertilization. With the exception of homes with a sunroom or greenhouse, few homes have areas with sufficient light levels to grow plants that require very high light (hibiscus, wax begonia, geranium). High light plants (weeping fig, English ivy, schefflera) can usually be grown well near windows or glass doors with western or southern exposures. Medium light plants (African violet, Boston fern, dumb cane) do well if placed within several feet of these light sources or in eastern exposures. Low light plants (peace lily, heart-leaf philodendron, cast-iron plant) can be placed several feet away from eastern exposures or in northern exposures. The amount of light at any given location will vary according to time of year (angle of the sun, day length), outdoor tree shading, window curtains and wall color (light reflection), as well as the location itself. Inexpensive light meters are available.Artificial lighting is widely used to supplement or replace natural light. Many indoor plants grow well under artificial light provided by fluorescent lamps or special incandescent lights. A large variety of fluorescent lamps are available. Generally, ordinary incandescent lamps are not recommended for plants, as plants placed under them tend to stretch or become “leggy.” It is possible to make up for lack of sufficient light by increasing the time or duration that the plant is exposed to light. Sixteen hours of light and eight hours of darkness are satisfactory for most plants. Use an electric timer to ensure the correct cycle each day.
While lack of sufficient light results in poor plant growth, too much light can also be harmful. Shade plants cannot tolerate excessively high light levels. When a plant receives too much direct light the leaves bleach or scald, sometimes dying. This often happens after moving a plant outdoors in direct light. Any changes in light intensity should be gradual.
Light requirements in footcandles (ft-c) for some common indoor plants
Low Light (100 ft-c) |
|
| Aglaonema commutatum | Silver Evergreen |
| Aglaonema commutatum cv. Silver King | Silver King Evergreen |
| Aglaonema modestum | Chinese Evergreen |
| Aspidistra elatior | Cast-iron Plant |
| Aspidistra elatior cv. Variegata | Variegated Cast-iron Plant |
| Chamaedorea elegans | Parlor Palm |
| Epipremnum aureum | Golden Pothos |
| Epipremnum aureum cv. Marble Queen | Marble Queen Pothos |
| Monstera deliciosa | Split-leaf Philodendron |
| Sansevieria trifasciata | Snake Plant |
| Sansevieria trifasciata cv. Laurentii | Goldband Sansevieria |
Medium Light (100 to 150 ft-c) |
|
| Aechmea fasciata | Silver Vase |
| Asparagus densiflorus cv. Myers | Plume Asparagus |
| Asparagus densiflorus cv. Sprengeri | Sprengeri Asparagus |
| Asparagus setaceus | Fern Asparagus |
| Aucuba japonica cv. Variegata | Gold-dust Plant |
| Brassaia actinophylla* | Schefflera |
| Brassaia arboricola* | Dwarf Schefflera |
| Caryota mitis | Fishtail Palm |
| Chamaedorea erumpens* | Bamboo Plant |
| Chlorophytum comosum cv. Variegatum | Spider Plant |
| Cissus rhombifolia | Grape Ivy |
| Dieffenbachia amoena | Giant Dumbcane |
| Dieffenbachia maculata | Spotted Dumbcane |
| Dizygotheca elegantissima | False Aralia |
| Dracaena deremensis cv. Warneckii* | Striped Dracaena |
| Dracaena fragrans cv. Massangeana* | Corn Plant |
| Dracaena godseffiana* | Gold-dust Dracaena |
| Dracaena marginata* | Red-margined Dracaena |
| Dracaena sanderana* | Ribbon Plant |
| Fatsia japonica | Japanese Fatsia |
| Ficus benjamina | Weeping Fig |
| Ficus elastica cv. Decora | India Rubber Plant |
| Ficus lyrata | Fiddle-leaf Fig |
| Ficus retusa | Indian Laurel |
| Gynura aurantiaca | Velvet Plant |
| Hedera helix and cultivars | English Ivy |
| Howea forsterana | Kentia Palm |
| Maranta leuconeura cv. Erythroneura | Red-veined Prayer Plant |
| Nephrolepsis exatata cv. Bostoniensis | Boston Fern |
| Peperomia caperata* | Emerald Ripple Peperomia |
| Peperomia obtusifolia | Oval-leaf Peperomia |
| Philodendron bipennifolium* | Fiddle-leaf Philodendron |
| Philodendron scandens subsp. oxycardium* | Heart-leaf Philodendron |
| Philodendron selloum | Tree Philodendron |
| Pilea cadierei | Aluminum Plant |
| Pilea involucrata | Friendship Plant |
| Plectranthus australis | Swedish Ivy |
| Polyscias balfouriana cv. Marginata | Variegated Balfour Aralia |
| Saintpaulia species, hybrids, and cultivars | African Violet |
| Spathiphyllum cv. Clevelandi | Cleveland Peace Lily |
| Spathiphyllum cv. Mauna Loa | Mauna Loa Peace Lily |
| Syngonium podophyllum cv. Trileaf Wonder* | Trileaf Wonder Nephthytis |
| Tradescantia fluminensis | Inch Plant |
| Zebrina pendula | Wandering Jew |
High Light (150 to 1000 ft-c) |
|
| Aloe barbadensis | Aloe Vera |
| Alternanthera ficoidea | Joseph’s Coat |
| Aphelandra squarrosa | Zebra Plant |
| Araucaria heterophylla | Norfolk Island Pine |
| Beaucarnea recurvata | Ponytail Palm |
| Cissus antarctica** | Kangaroo Vine |
| Citrofortunella mitis | Calamondin Orange |
| Coffea arabica | Coffee |
| Coleus blumei | Coleus |
| Cordyline terminalis | Ti Plant |
| Crassula argentea | Jade Plant |
| x Fatshedera lizei** |
Botanical Wonder |
| Hibiscus rosa-sinensis | Chinese Hibiscus |
| Hoya carnosa** | Wax Plant |
| Iresine lindenii | Blood Leaf |
| Podocarpus gracilior | Weeping Pododarpus |
| Polyscias fruticosa | Ming Aralia |
| Rhoeo spathacea | Moses-in-the-Cradle |
| Schlumbergera cv. Bridgesii | Christmas Cactus |
| Sedum morganianum | Burro’s Tail |
*May also be conditioned to grow in low light. **May also be conditioned to grow in medium light.Excerpted from the South Carolina Master Gardener Training Manual, EC 678.
Prepared by Debbie Shaughnessy, HGIC Information Specialist, and Al Pertuit, Extension Floriculture Specialist, Clemson University.
This information is supplied with the understanding that no discrimination is intended and no endorsement by the Clemson University Cooperative Extension Service is implied. All recommendations are for South Carolina conditions and may not apply to other areas. Use pesticides only according to the directions on the label. All recommendations for pesticide use are for South Carolina only and were legal at the time of publication, but the status of registration and use patterns are subject to change by action of state and federal regulatory agencies. Follow all directions, precautions and restrictions that are listed. (New 9/99).
Peach Insect Pests
Numerous insects are pests on peach trees in South Carolina. They cause damage to the peach flowers, fruit, twigs, limbs and trunk. Some of the most common of these are plum curculio, Oriental fruit moth, peachtree borer, lesser peachtree borer, shothole borer, catfacing insects, scale, Japanese beetle and the green June beetle.
As a result of the need to control some serious insect pests as well as disease organisms, individuals who grow peaches in their backyard for home use often discover that obtaining acceptable quality fruit requires more specialized care than they can give. It should be noted that without the application of well-timed pesticides, it is common for insect pests and disease to ruin the entire crop as well as damage the tree(s).
Several all-purpose fruit sprays are on the market for homeowner use. These materials contain an insecticide and fungicide that will control most insects and diseases seen in a home orchard fruit tree situation. As with any pesticide, read and follow all label directions and precautions.
Aside from pesticides, homeowners can follow such cultural practices as proper sanitation to reduce insect pests significantly. Sanitation includes quickly removing and destroying dead, diseased and damaged wood and fruit. The leaves, wood and fruit often provide pests with places to complete their development or to survive the winter.
Although adequate insect control on peaches usually requires spraying trees, these sprays need to be timed accurately to be effective. Knowledge of the insect pests and their life cycles aids in identification as well as the early diagnosis of a developing pest problem.
Plum Curculio
The adult plum curculio (Conotrachelus nenuphar) beetle is a mottled brown with a rough and warty body surface. It is about ¼ inch long and has a long, curved snout. Its immature stage is a grub (larva). A fully mature grub is legless, smooth-bodied and up to ½ inch in length. It is yellowish to grayish in color and slightly curved with a brown head.
Both adults and grubs cause damage to peaches, as well as plums and other stone fruits, apples and occasionally pears. The primary injury is caused by the adult female when she makes a crescent-shaped cut in the skin of the fruit to lay her eggs. This results in D-shaped scars on the fruit surface. Grubs that hatch from the eggs feed in the fruit making it worthless. Later in the season both males and females damage the fruit by making round feeding punctures.
Plum curculio adults overwinter (survive the winter) under leaves, brush and in other protected places near the orchard. Wild plum thickets within ¼ mile of an orchard can provide a source of adults. The adults become active when mean temperatures reach 50-60 degrees F for three to four days, or when the maximum temperature reaches 75 degrees F for two or more days. This is usually about the time peach trees bloom. The first activity will be noticed on outside rows.
They feed on developing fruit and leaves and lay their eggs in the young fruit. Carefully inspect fruit on these outside rows for egg-laying and feeding scars. Fruit infested shortly after bloom by the first generation drop to the ground. The larvae hatch and feed in the fruit. They leave the fruit, burrow into the ground and pupate (transform into the nonfeeding stage where the larva changes into an adult). From mid-June through July the first generation adults emerge, move into the trees, and begin laying eggs. Fruit infected by the second generation remain on the tree until harvest. Again the larvae feed for a while, drop to the ground and pupate. The second generation adults emerge in the fall, move to the hibernation areas and overwinter.
When disturbed, the adult plum curculio tends to fold its legs against its body and fall to the ground where it remains motionless for several minutes. This behavior can be used when trying to detect its presence. Place a light colored drop cloth on the ground under the tree and shake some branches. If present, the plum curculio will drop to the ground and be readily visible.
Control: Homeowners can achieve at least partial control by practicing good sanitation methods. These include picking up and destroying fruit that drops early, as well as removing or cleaning up overwintering sites.
Chemical controls should be applied immediately after the flower petals fall to control the first generation. Three sprays, the first in mid-June and the second at the end of June and the third in early July will control the second generation adults. Homeowners can use carbaryl (Sevin) or malathion. Insecticides may be used individually, or can often be found in premixed home orchard spray products, such as Bonide Fruit Tree Spray. When using carbaryl or malathion, wait 3 or 7 days, respectively, between spray application and harvest. Permethrin (Bonide Eight Vegetable Fruit & Flower Concentrate, Bonide Eight Insect Control Yard & Garden Ready-to-Spray and Bonide Borer-Miner Killer Concentrate) or esfenvalerate (Ortho Bug-B-Gon MAX Garden & Landscape Insect Killer Ready-to-Use) may also be used to control plum curculio, but do not apply these products within 14 days of harvest. Repeated use of carbaryl, permethrin or esfenvalerate may increase problems later in the season with scale or mite outbreaks. A mixture of neem oil and pyrethrins, such as in Green Light Fruit Tree Spray, is labeled for plum curculio control. As with all pesticides, read and follow all label directions and precautions.
Oriental Fruit Moth
The Oriental fruit moth (Grapholita molesta) is grayish-brown and has a wingspan of about ½ inch. It is active at night. When first hatched, its caterpillar (larva) is about 1/16-inch long and white with a black head. The mature caterpillar is about ½-inch long, has six distinct legs and is pinkish with a brown head. The caterpillar is a pest of peaches and other stone fruits as well as apples, pears, and some ornamentals in the rose family.
In South Carolina, there are six or more generations of Oriental fruit moth per year. This pest overwinters as mature larvae inside cocoons, which are located in protected areas on the tree or in debris near the base of the tree. In early spring, the larvae pupate (transform into the nonfeeding stage where the larva changes into an adult) and adults begin to emerge at about the time of bloom. The adults lay eggs from which larvae hatch. These first-generation caterpillars bore into new growth at the tips of peach tree branches. This activity causes the branch tips to wilt (also known as “flagging”) and die back. Later in the season, after the branch tips harden, caterpillars enter and feed in the fruit instead. While in the fruit and twigs, caterpillars are protected from insecticides. Good early season control of adult moths using insecticides will often provide control for the entire season.
Control: The presence of moths can be detected with the use of traps containing pheromones (synthetic insect attractants). Permethrin sprays (Bonide Eight Vegetable Fruit & Flower Concentrate, Bonide Eight Insect Control Yard & Garden Ready-to-Spray and Bonide Borer-Miner Killer Concentrate) or esfenvalerate (Ortho Bug-B-Gon MAX Garden & Landscape Insect Killer Ready-to-Use) should be applied if an average of more than 10 moths per trap occurs. Do not apply these products within 14 days of harvest, and do not apply more than 8 applications of permethrin per season for all insect pests.
Peach borers
The peachtree borer (Synanthedon exitiosa), the lesser peachtree borer (Synanthedon pictipes), and the shothole borer (Scolytus rugulosus) are pests of peaches. Of these, the peachtree borer and lesser peachtree borer are the more serious pests. They are found on most cultivated and wild stone fruits, including some ornamental shrubs such as flowering peach, cherry and plum. It is the larvae of these insects that damage peach trees.
Peachtree Borer: The peachtree borer adults are clearwing moths, and are often mistaken for wasps due to their appearance and behavior. The adult female peachtree borer is a metallic blue-black color except for a red-orange band on the abdomen. The male is black with yellow stripes along the back at the base of each wing and narrow yellow stripes on the abdomen. The larva (immature stage) is about 1 to 1¼ inches long when fully grown. It is creamy white with a brown head.
The larva of the peachtree borer attacks the tree at the base and may be found feeding from the main roots to about 10 inches up onto the trunk. Masses of gum mixed with frass (a sawdust-like insect waste) are the primary symptoms of attack. Young trees can be killed by a very small number of larvae. Older trees can tolerate more larvae.
The peachtree borer overwinters (survives the winter) as larvae. It has one generation per year. Some adults begin emerging in late May although peak emergence is in mid- to late August. Wounds and rough bark are favorite sites for egg laying. About two weeks after the eggs are laid at the base of the tree, the small larvae hatch, burrow into the bark and begin feeding. They stop feeding when cold weather comes and resume feeding the following spring.
Control: Since the peachtree borer causes its most severe damage to young trees, special care must be taken during planting to avoid damaging the bark. A pre-plant dip in an insecticide solution is strongly recommended. In light soils the wind may make the tree move enough to make a gap between the trunk and the soil or abrade the bark. This is an excellent entry site for the larvae. Annual trunk sprays during August will generally keep the peachtree borer under control. Be sure to apply sufficient spray from the scaffold limbs to ground level so the bark is saturated and a small puddle forms at the base of each tree.
Homeowners can use permethrin (Green Light Borer Killer, Bonide Eight Vegetable Fruit & Flower Concentrate, Bonide Eight Insect Control Yard & Garden Ready-to-Spray and Bonide Borer-Miner Killer Concentrate) or esfenvalerate (Ortho Bug-B-Gon MAX Garden & Landscape Insect Killer Ready-to-Use) for peachtree borer control. Do not apply these products within 14 days of harvest. Bifenthrin (Ortho Bug-B-Gon MAX Lawn & Garden Insect Killer Concentrate) may be used only on small non-fruit bearing trees. As with all pesticides, read and follow all label directions and precautions.
Lesser Peachtree Borer: The adults of the lesser peachtree borer are also clearwing moths. Both the male and female adult lesser peachtree borers resemble the male peachtree borer except that they are somewhat smaller. The larva of the lesser peachtree borer is very similar to the larva of the peachtree borer but smaller.
The lesser peachtree borer attacks the trunk and main limbs. Again the symptoms are oozing gum that contains frass. Heavy infestations can kill individual limbs or an entire tree.
Like the peachtree borer, the lesser peachtree borer overwinters as larvae. It, however, has two generations per season and occasionally, a third. Emergence of adults peaks in late April to mid-May and late July to mid-August. Cytospora cankers (a fungal disease), wounds, and previously infested areas are favorite sites for egg laying.
Control: The best control for the lesser peachtree borer is to keep the trees in a vigorous, healthy growing condition and to prevent mechanical injury. Prune out split or broken limbs and limbs with signs of borer damage where feasible. Destroy pruned wood before adults emerge in April by shredding or burning. Avoid spreading bacterial canker while pruning by dipping the pruning tool after each cut into a solution of one part household bleach to nine parts water.
As with the peachtree borer, annual trunk sprays in August will help control the lesser peachtree borer. However, since there are two or more generations per year it is difficult to get good control with insecticides since the first generation emerges while there is fruit on the tree. Homeowners can use permethrin, bifenthrin or esfenvalerate for lesser peachtree borer control (see products and limitations listed for peachtree borer control). Do not apply these products within 14 days of harvest. As with all pesticides, read and follow all label directions and precautions.
Shothole Borer: Shothole borers are small, cylindrical beetles. They attack many fruit trees and ornamental trees and shrubs. Plants under stress are highly susceptible to shothole borer attack. Shothole borers attack the trunk and limbs. The entry holes look like the tree has been hit with fine bird shot. The adult beetle bores into the bark and then carves out chambers below the bark in which to lay eggs. The larvae feed on the bark. Occasionally, shothole borers may attempt to enter the twigs at the base of flower buds. This activity can destroy the buds.
The shothole borer overwinters as larvae. It has several generations per year. The adults emerge from the infested trees in April and May and move to new trees, especially those under stress from drought, disease or other reasons.
Control: The best control for shothole borer is to keep the trees in a vigorous, healthy growing condition and to prevent mechanical injury. Prune out split or broken limbs and limbs with signs of borer damage where feasible. Destroy pruned wood before adults emerge in April by shredding or burning. Avoid spreading bacterial canker while pruning by dipping the pruning tool after each cut into a solution of one part household bleach to nine parts water.
Permethrin, bifenthrin or esfenvalerate sprays that are necessary for other borers provide adequate control of adults (see products and limitations listed for peach tree borer control). Do not apply these products within 14 days of harvest. As with all pesticides, read and follow all label directions and precautions. With more than one generation per year it is difficult to get good control with insecticides since the first generation emerges while there is fruit on the tree. There is no effective control for insects already in the tree.
Catfacing Insects
Catfacing insects include the tarnished plant bug (Lygus lineolaris) and various stink bugs. The tarnished plant bug is oval and has a white triangle on its back in the “shoulder” area. It is brown and about ¼-inch long. Stinkbugs are shaped like a shield. They vary in color from green to brown and in size from ½ to ¾ inch in length.
The tarnished plant bug and the stink bugs have needlelike mouthparts that they use for piercing and sucking. They distort fruit by their feeding. The damage that they cause appears as deep dimples in the fruit. The damage is cosmetic and the fruit is still edible.
The catfacing insects overwinter as adults in protected areas in or near the orchard. Winter annual weeds that begin to bloom in late winter are a major attractant for these insects.
Control: Removing weeds and debris in the area will greatly enhance control of these insects. For chemical control, carbaryl (Sevin 50WP) is available in homeowner size packaging, as are permethrin (Bonide Eight Insect Control Vegetable Fruit & Flower Concentrate, Bonide Eight Insect Control Yard & Garden Ready-to-Spray) or esfenvalerate (Ortho Bug-B-Gon MAX Garden & Landscape Insect Killer Ready-to-Use). Do not apply these products within 14 days of harvest, or carbaryl within 3 days of harvest. As with all pesticides, read and follow all label directions and precautions.
Scale
Various scale insects attack peaches. The most commonly seen are the white peach scale (Pseudaulacaspis pentagona) and the San Jose scale (Quadraspidiotus perniciosus). These immobile insects can rapidly decrease the vigor of peach trees, kill limbs and ultimately kill the trees.
Scales are unusual insects in appearance. The adults are small and immobile, with no visible legs. Scales vary in appearance depending on age, sex and species. The adult females typically produce a waxy covering that protects them from many insecticides. They feed on sap by piercing the leaf or stem with their mouthparts and sucking.
The adult female white peach scale is 1/16 to ⅛ inch in diameter. It is circular in shape and yellowish to grayish white with a yellow or reddish spot. It will infest the bark, fruit and leaves of peach trees. An infestation by white peach scale can result in stunting, leaf drop, death of branches and even entire trees.
The white peach scale survives the winter as an adult female. The adult male is mobile and lives about one day. After mating, the female starts laying eggs in early April. The eggs hatch into nymphs (immature stage that looks similar to adult only smaller). Nymphs, or crawlers, as they are also called, crawl around for a few days before settling and beginning to feed. There are three generations per year.
The San Jose scale survives the winter as partially developed male and female adults. Development continues when the sap flow begins in the spring, and they become fully developed about the time the peach trees are in bloom. This species does not lay eggs but gives birth to crawlers that immediately disperse over the tree. There are four to six generations per year.
Control: The adult female scales are difficult to control with insecticides because of their hard, waxy covering. Horticultural oil or dormant oil can be applied before budbreak when the temperature is above 40 °F. These oils work by smothering the overwintering adult females, and they offer the best control when applied during the dormant season. Spray the trunk and limbs with 1 to 2% oil solution to the point of run-off. If the scale problem is serious, fall applications applied during the first cool spell after full leaf drop should be considered. These oil sprays during the dormant season will also help control mite infestations, as they survive the winter on the bark.
Chemical control of the crawlers only can be achieved with malathion, carbaryl, permethrin or esfenvalerate which are available in homeowner size packaging (see products, limitations and pesticide comments listed for peach tree borer control). Additionally, sprays for controlling scale should be applied about April 9, June 25, August 25, and October 8 in the Savannah Valley and Pee Dee regions, and about May 1, July 1, and September 1 in the Piedmont. Do not spray insecticides during bloom. Do not apply malathion within 7 days of harvest, carbaryl within 3 days of harvest, and permethrin or esfenvalerate within 14 days of harvest. As with all pesticides, read and follow all label directions and precautions.
Prepared by Clyde S. Gorsuch, Extension Entomologist, and J. McLeod Scott, HGIC Horticulture Information Specialist, Clemson University. Revised by Joey Williamson, HGIC Horticulture Information Specialist, Clemson University
Sweet Corn Diseases
Sweet corn is seldom seriously damaged by diseases in the home garden. Reduce many of the potential disease problems by following proper cultural practices including:
- Using commercially grown certified and treated seed to improve stands.
- Planting varieties recommended for South Carolina (see HGIC 1308, Corn).
- Planting corn when the soil temperature is above 55 °F to reduce most seedling rots.
- Keeping the garden free of nearby weeds, which can harbor viruses.
- Removing smutted corn ears promptly from the stalks and garden area.
- Removing corn plant debris after harvest to reduce diseases caused by rusts and corn smut.
Remember, preventing corn diseases in the garden is very important, since the rapid growth of sweet corn makes it very difficult to spray adequately with chemicals. More information on how to grow corn is available in the fact sheet HGIC 1308, Corn.
CORN SMUT
This disease is easy to find in the garden. Large, fleshy, brownish galls (swellings) containing a black sooty mass of spores develop on leaves, stems, ears or tassels. Young immature galls are white or grayish white. A fungus, Ustilago maydis, causes this disease which occurs throughout the Southeast, especially when temperatures are high (79 to 100 °F) and moisture is abundant. Prevention and Treatment: Pick off and destroy infected ears and galls while they are immature and have not yet released spores. Remove galls carefully, since spores can readily blow to nearby plants, causing more disease. Corn smut overwinters on plant debris in the soil, so do not put infected crop residues back into the soil. The most susceptible plants are those grown in soils high in nitrogen. No chemical controls are available.
RUST
Rust occurs in most home gardens on corn but is seldom a serious problem. It is caused by various species of the fungus Puccinia and causes raised, brick red spots primarily on upper leaf surfaces. Plant corn early, and avoid letting plants get under stress from drought. Rust develops best when temperatures are cool (60 to 70 °F) and humid.
SEED ROTS AND SEEDLING DISEASE
Poor stands of corn can result from various species of fungi, including Pythium, Fusarium, Diplodia and Penicillium, which affect seed germination and seedling development. In cold soils that have a temperature less than 55 °F seeds can decay and seedlings may die before they reach the soil surface. In cool, wet soils seed germination and seedling development slows down, increasing the length of time exposed to fungi in the soil. Low-quality seed also produces seedlings that are weak and survive poorly, especially in cold soils. In warmer soils, seedlings may emerge, but have rotted roots and stems at the ground line.Prevention and Treatment: Control of these problems is obtained by using high-quality seed that has been treated with protective fungicides. Seeds will be pink to indicate they have been treated. Sweet corn should be planted on a raised bed, after the soil temperature is above 55 °F.
VIRUS DISEASES
In South Carolina there are two main viruses that are a problem on corn, Maize dwarf mosaic virus (MDMV) and Maize chlorotic dwarf virus (MCDV). Symptoms of these virus diseases can easily be mistaken for other growth problems such as nutrient deficiencies. The upper leaves of MDMV-infected plants show pale green blotches or mottling. MCDV-infected leaves often have a pale green streaking of the upper leaves, and often these leaves turn a reddish color. Both virus diseases generally cause plant stunting. The viruses survive the winter on many perennial grasses, especially Johnsongrass. In the spring, insects transmit the virus to young corn plants. Prevention and Treatment: Control grassy weeds near corn plantings (Johnsongrass). Corn planted at the appropriate time, and not too late in the season, is often damaged less by viruses. There is no chemical control available.
ROOT AND STALK ROTS
Root and stalk rots are among the most destructive corn diseases. They are caused by various species of fungi, including Fusarium, Diplodia, Pythium and Macrophomina. Infected corn stalks fall over (lodging) and losses result from unharvested ears and poor ear development on infected plants. Some of these disease-causing organisms enter through the roots and move up into the stalk, while others enter the stalk directly at the nodes. Insect damage can increase infection by wounding the plant and allowing fungi to enter. Prevention and Treatment: Plant in well-drained areas, because stalk rots are most severe in poorly drained soil and where poor air movement slows drying. Do not exceed recommended plant densities. Keep soil fertility balanced based on soil tests. All insect controls should be carefully followed as described in HGIC 2205, Insect Pests of Sweet Corn.
SOUTHERN CORN LEAF BLIGHT
This disease is caused by the fungus Helminthosporium maydis. Symptoms occur as leaf spots or cob rots and are fairly easy to recognize on plants. Spots on the leaves are tan to light brown and occur first on the lower leaves of the plant. Spots often enlarge and increase in number and can cause severe leaf blighting. On the ear the fungus causes oblong, bleached spots which penetrate through the shuck layers and finally into the ear .Prevention and Treatment: Rotate corn with nongrass-type plants in the garden. Turn under corn debris soon after harvest to promote rapid decay and destroy overwintering fungi.
STEWART’S WILT (BACTERIAL WILT)
This disease causes death of seedlings and wilting of mature plants. Long rectangular streaks, up to an inch wide, appear on the leaves, which later turn brown and die. A brown cavity is often formed inside of the stalk at ground level. It is caused by a bacterium, Erwinia stewartii, which survives the winter in flea beetles. Healthy plants become infected when the beetles begin feeding on them. Prevention and Treatment: There is no effective chemical control available for this disease. Remove and destroy all infected plants immediately. Controlling the insects that spread the disease can reduce disease levels. More information is available in HGIC 2205, Insect Pests of Sweet Corn.
NEMATODES
Nematodes are microscopic roundworms that live in the soil and can feed on corn roots. They can damage the root system to the point where it cannot properly absorb water and nutrients. Above-ground symptoms include stunting and nutrient deficiencies. Below the soil surface, affected roots appear stubby, swollen, and often have an absence of small feeder roots. Nematode damage can only be confirmed by having your soil analyzed. Samples can be submitted to your local county Extension office for determination of the type and degree of infestation.Prevention and Treatment: An effective nematode control program should include crop rotation, sanitation and solarization. More information about controlling nematodes in the home garden is available in HGIC 2216, Root-Knot Nematodes in the Vegetable Garden.Diseases and Insects of Corn in South Carolina, EC601.
Prepared by Nancy Doubrava, HGIC Information Specialist, and James H. Blake, Extension Plant Pathologist, Clemson University.
This information is supplied with the understanding that no discrimination is intended and no endorsement by the Clemson University Cooperative Extension Service is implied. Brand and common names of pesticides are given as a convenience and are neither an endorsement nor guarantee of the product nor a suggestion that similar products are not effective. Use pesticides only according to the directions on the label. All recommendations for pesticide use are for South Carolina only and were legal at the time of publication, but the status of registration and use patterns are subject to change by action of state and federal regulatory agencies. Follow all directions, precautions and restrictions that are listed. (New 5/99).
Soil Solarization for Control of Soil-Borne Pathogens & Weeds
Soil solarization is a non-chemical method for controlling weed seeds, bacteria, fungi, and nematodes. As a non-chemical control method it fulfills many gardeners’ wishes for organic or low toxicity control. It is a potential alternative to chemical fumigation.
Soil solarization is usually only considered as a remedy for challenging problems in the home garden. This is because the treated area will be out of production for nearly 2 months during the summer growing season. The basic procedure is to cover the soil with a clear plastic and trap the sun’s heat to raise soil temperatures high enough to kill weed seeds and harmful plant disease organisms.
Solarization can be applied in many areas of the home landscape, but no plant material can be present in the area to be solarized. The extremely high soil temperatures will kill any plants left in the solarized area, and plant remains will interfere with even heating.
Vegetable garden plots and annual flowerbeds are the best areas for control. The larger the plot area the better control achieved. Treated areas greater than 30 inches wide seem to have the best results. Areas smaller than 30 inches have a cooling affect on the outer edges.
PROCEDURE
Soil solarization works well in South Carolina because of the high temperatures during the summer months. The warmer the climate during the growing season and the longer you have to leave the plastic in place, the better results you will obtain. Long periods of heating are necessary to achieve good control of hard-to-kill weeds like crabgrass and nutsedge.
Soil Preparation: The first step in the solarization process is to cultivate the bed and prepare it for planting to avoid disturbing the soil afterwards. Disturbing the soil afterwards will bring weed seeds to the surface that have not been affected by the heat treatment. Only the top 2-3 inches of soil receive the greatest results. Apply fertilizer or irrigation equipment that will be needed prior to solarization.
Till the soil thoroughly, 6-8 inches deep, to destroy all large clods and remove any existing plant material. Leaving clods or plant material will interfere with uniform conduction of heat through the soil, allowing some pests to remain protected from the effects of the treatment. A well-tilled, smooth surface provides good contact between the plastic mulch and the soil surface.
Irrigation: Next, after the bed is cultivated and raked smooth, irrigate the area. This is a very important step in the process. Soil moisture is required for two different reasons, (1) to increase the transmission of heat through the soil, and (2) to make seeds and other resting structures more sensitive to high temperatures. Seeds are very heat resistant when dry.
A sprinkler or drip-line irrigation line gives the best results. Water the soil heavily so that it is wet, yet without standing puddles. Once the soil has been irrigated there is no need to irrigate after laying the plastic.
Trenching: Dig a trench approximately 6-8 inches deep and wide around the perimeter of the plot. The trench will be used to bury the edges of the plastic to be placed over the plot.
Covering: Cover the soil with clear UV stabilized plastic (polyethylene or PVC), and bury the edges in the trench. Stretch the plastic as tightly as possible. Once the plastic is in place, refill the trench, covering and sealing the plastic edges. This will ensure that the plastic is held in place and will prevent heat from escaping or allowing wind to get beneath. Bricks or stones can be used to further protect the edges against wind or other disturbance.
A double layer of plastic will increase the effectiveness of solarization. An air gap should be created between the two layers of plastic giving extra insulation. This air gap can be maintained by placing objects such as empty soda pop cans between the layers of plastic.
The time needed to get high levels of control is dependent on temperature. Using clear polyethylene allows sunlight to pass through directly to heat the soil. Thin clear plastic (1-2mil) allows more sunlight to pass through and penetrate the soil. Thin clear plastic favors more rapid and deep heating of the soil than does black plastic.
Leave the plastic in place for 4-8 weeks during the hottest part of the summer. In South Carolina the best time to solarize your soil is from June through August. The effectiveness of soil solarization is determined by the combination of soil temperature and exposure time. With increasing temperature, less time is needed to reach a lethal combination of time and temperature.
Excess time under solarization will not be harmful to your plot. If you are not planning to plant immediately, leaving the plastic in place can only maximize the treatment and will act as a barrier against recontamination.
Removing Plastic and Planting: After your plot has been exposed to high temperatures for 4-8 weeks, the plastic mulch can be removed. Removal of the plastic should be done very carefully without disturbing the soil. Do not re-till the soil. This will bring weed seed and plant disease organisms from depths that were not affected by the treatment and recontaminate the plot.
This is why any soil preparations like fertilization or irrigation systems should have been completed prior to covering with the plastic.
Disposal of the plastic can be considered an environmental pollution problem. The clear polyethylene plastic is able to withstand the high temperatures it is exposed to better than black plastic. The plastic can be taken up and saved for a second treatment. A second use for the plastic would be to paint the clear plastic white as mulch for tomatoes, peppers and other plants, which would benefit from the higher soil temperatures in the fall. If you are planning to plant crops that need cooler soil temperature, the plastic should be completely removed in time for the soil to cool before planting.
Once you have removed your plastic mulch you are ready to plant. If you are not planning to plant until the following spring, cover the area with weed-free mulch and avoid activities that will disturb the soil.
FACTORS THAT INFLUENCE SUCCESS
Soil characteristics such as color, structure, and depth have an effect on the effectiveness of soil solarization. Dark colored soil tends to adsorb more solar radiation in comparison to light colored soils. Loose, friable soils enable heat to be transmitted throughout the soil and allow heat to go deeper. Control is much better in the top few inches of the soil and decreases with soil depth.
The level of control achieved depends on a combination of the duration of the solarization process, the high temperatures reached and the susceptibility of the weed species to be controlled. Fungi that live in the top 2-3 inches of soil, like Rhizoctonia or the Southern blight fungus, are easier to control with solarization than other plant disease organisms.
Prepared by C. Lindsay, Horticulture Student, Karen Russ, HGIC Information Specialist, and Dr. Anthony P. Keinath, Extension Vegetable Pathologist, Clemson University.
This information is supplied with the understanding that no discrimination is intended and no endorsement by the Clemson University Cooperative Extension Service is implied. All recommendations are for South Carolina conditions and may not apply to other areas. Use pesticides only according to the directions on the label. All recommendations for pesticide use are for South Carolina only and were legal at the time of publication, but the status of registration and use patterns are subject to change by action of state and federal regulatory agencies. Follow all directions, precautions and restrictions that are listed. (New 10/03).
