Terminology Of Soil Fertility, Fertilizer And O...
The depletion of soil has affected the state of plant life and crops in agriculture in many countries. In the Middle East for example, many countries find it difficult to grow produce because of droughts, lack of soil, and lack of irrigation. The Middle East has three countries that indicate a decline in crop production, the highest rates of productivity decline are found in hilly and dryland areas. Many countries in Africa also undergo a depletion of fertile soil. In regions of dry climate like Sudan and the countries that make up the Sahara Desert, droughts and soil degradation is common. Cash crops such as teas, maize, and beans require a variety of nutrients in order to grow healthy. Soil fertility has declined in the farming regions of Africa and the use of artificial and natural fertilizers has been used to regain the nutrients of ground soil.
Terminology of soil fertility, fertilizer and o...
The increasing use of conservation tillage, no-till, and cover crops is changing the way we view the soil and the environment. New concepts and terminology are being used to describe these changes. Understanding the terms defined in this fact sheet will help farmers understand relationships between tillage, crop rotation, cover crops, carbon sequestration, organic matter pool, agricultural sustainability, and soil and water quality.
Sustainable agriculture and soil quality are terms that are increasingly important to modern farming. With higher costs for labor, seed, fuel, fertilizer, and pesticides, agricultural producers are looking for more economical ways to improve crop production and maintain ecosystem sustainability.
Microbial Biomass: Includes the smallest living organisms such as bacteria, fungus, protozoa, algae, actinomycetes, nematodes, and nonliving organisms: prion and viruses. Microbial biomass denotes a small portion (less than 5%) of soil organic carbon. The main function of the microbial biomass is to act as bio-catalyst for organic matter decomposition and mineralization, soil fertility, and humus formation and soil aggregation.
Mycorrhizae: Literally means "fungus root" and is a symbiotic (mutually beneficial) relationship between fungus and plant roots. The fungus supplies water and nutrients to the plant roots while the plant supplies carbohydrates. Plant roots typically can explore no more than 1% of the soil volume but with mycorrhizal fungus (which attach themselves to the plant root cell walls) association, approximately 20% of the soil volume may be explored. Over 80% of plants have a mycorrhizal association but these fungus populations are reduced by conventional tillage and high fertilizer applications of nitrogen and phosphorus.
No-Till: A system where the crop is planted directly into a seedbed without tilling or disturbing the entire soil surface. The only soil disturbance is for placement of seed and fertilizer. This system is also called zero-till or direct seeding. No-till farming, by definition, means that the soil has not been disturbed since the prior harvest of a crop. Continuous no-till means the soil has not been disturbed for several years.
Ammonium N (NH4+-N): A water-soluble form of nitrogen (N) that is present in some fertilizers. Ammonium N (NH4+-N) can be converted to ammonia gas and lost to the atmosphere if left on the soil surface. Therefore, fertilizers containing NH4+-N should be watered in.
Controlled-release fertilizers: Water-soluble inorganic fertilizers that have been modified to allow for controlled release of nutrients over time. The rate, pattern, and duration of nutrient released from a controlled-release fertilizer is well documented (Shaviv, 2000). In many controlled-release fertilizers, the water-soluble fertilizer materials are encapsulated in a plastic or polymer coating. Nutrients are released over time; the amount of time it takes for nutrients to be fully released depends on the nature of the coating, contact with moisture, and temperature. It is important to choose a controlled release fertilizer that has a release rate that matches the plants' nutrient needs. Typically, nutrient release from controlled-release fertilizers increases with increasing temperature and soil moisture. Examples of controlled release materials are Osmocote and Polyon.
Nitrate N (NO3--N): A water soluble form of N that is present in some fertilizers. If not managed properly, this form of N can be a concern for water quality. The chemical properties of NO3--N allow this N form to be leached (or moved downward) through the soil. Nitrate leaching often impacts groundwater and springs. High NO3--N concentrations in groundwater can be a human health hazard. Nitrate may also lead to degradation of sensitive water bodies.
Organic fertilizers: Organic fertilizers are materials that are derived from living materials. Examples of organic fertilizers include animal manures, composted materials, and plant residues. Organic fertilizers are usually considered to be "slow-release" fertilizers because many of the nutrients must be broken down by soil microbes before they become available for plant uptake.
Soil testing provides valuable information on pH and plant-available nutrients. Test your soil before planting and every two to three years thereafter. Inexpensive soil test kits are unreliable. To accurately determine your soil characteristics and the proper amount of lime and fertilizer to apply, contact the NC Department of Agriculture & Consumer Services (NCDA&CS). The accuracy of these reports, however, depends on the quality of the sample submitted.
Fertilizing trees and shrubs in a landscape should be based on the amount of rainfall, soil type, the plant's age, the amount of current growth, and desired future growth. Overapplication of fertilizer to home landscapes wastes money, contributes to pollution in our rivers, streams, lakes, and estuaries, and may damage or kill desired plants.
Many people confuse plant nutrition with fertilization. Plant nutrition refers to the needs of the plant and how a plant uses the basic chemical elements. Fertilization is the term used when these elements are supplied to the soil as amendments. Adding fertilizer during unfavorable growing conditions will not enhance plant growth and may actually harm or kill plants.
Fertilizers provide some elements that might be lacking in the soil and stimulate healthy, vigorous growth. How much and when to apply fertilizers should be based on observing plant performance, a reliable soil test, and an understanding of the factors that affect growth: light, water, temperature, pests, and nutrition. Simply applying fertilizer because a plant is not growing adequately will not solve many plant problems (insects, disease, or poor drainage, for example), and, in fact, excess nitrogen can often increase insect and disease infestation.
Natural fertilizers typically release nutrients at a slower rate and over a longer period than synthetic fertilizers because microorganisms are involved in a breakdown and release cycle called mineralization. Moisture, temperature, and the microbial species and populations in the soil affect mineralization. Some water-soluble natural fertilizers, such as fish emulsion, are available when rapid nutrient delivery is desired.
Natural fertilizers can be expensive if applied in amounts adequate to supply nutrients for good plant growth, but have the added benefit of improving soil structure and plant vigor. When applying natural fertilizers, calculate as closely as possible the amounts of nutrients being supplied. Always err on the low side of application rates, then test the soil and augment as recommended on the soil test report. The nutrient content may need to be supplemented with other natural or synthetic materials to achieve a balanced ratio of nutrients.
Incomplete fertilizers can be used separately or combined to supply the needed nutrients, often at a reduced cost compared to using a complete fertilizer. For example, gardeners who have a soil with sufficient P and K can save money by applying a nitrogen-only fertilizer, such as ammonium nitrate (34-0-0). If a soil test indicates N and K are needed, but not P, use an appropriate amount of ammonium nitrate and muriate of potash (0-0-60), a naturally occurring material composed almost entirely of potassium, processed to remove impurities and concentrate the product. If a soil needs only P, use triple super phosphate (0-46-0), or for an organic nutrient source apply bone meal (approximately 3-15-0; note that this will add some N) or compost.
Fertilizer misuse causes environmental and water quality issues. Nitrogen fertilizers, for instance, break down into ammonium and nitrate. The nitrate form of N, while essential for plant growth, is highly mobile and can move through the soil after rainfall or irrigation and contaminate drinking water supplies. Phosphorus holds tightly to soil particles and does not leach through the soil, but affects water quality through runoff and soil erosion. Excess nitrogen and phosphorus are associated with algal blooms (heavy growth of aquatic plants) and limited oxygen, and cause fish kills in lakes, bays, and non-flowing water bodies.
Soil type affects the frequency of fertilizer application. Sandy soils require more frequent applications of smaller amounts of nitrogen and potash than do clay soils because these nutrients leach more readily in sandy soils. Other factors that affect application frequency include the plant to be grown, the amount of plant growth desired, the amount of water, and the type and release rate of fertilizer applied.
Research has shown it is best to broadcast or incorporate fertilizer uniformly over an area rather than concentrating fertilizer in holes or bands in the soil. The most effective method of fertilizing a large area is with a fertilizer spreader; for home gardens, hand fertilization works fine. For new plantings, incorporate fertilizer into the soil and mix it thoroughly. For established plantings, surface application is appropriate. 041b061a72