The quest for increased economic returns in crop production mandated the need in searching for innovative ways to increase crop yield. Increasing crop yield is a function of properly aligned factors. Factors such as:
a. Seed quality
b. Soil fertility
c. Environmental factors
d. Others.
Today’s focus will address soil fertility.
A soil is said to be fertile if it contains the nutrients requirement of a particular crop. The nutrient has to be readily available in sufficient quantity and quality. All soils naturally contain nutrients. Examples of such nutrients are Nitrogen, Phosphorus, Potassium, Sulphur, Calcium, etc.
Literature in crop and soil science has grouped these nutrients into two groups macronutrients and micronutrients. Macronutrients (N, P, K) are needed in large quantities while micronutrients (Ca, S, Mn, Mg, etc.) are needed in small quantities.
The challenge with soil fertility is that soils most times do not have the nutrients needed by crops either in form of availability or quality. Soils lose nutrients as a result of many interactions between human activities and agricultural activities. Activities such as land degradation, erosion, bush burning, grazing, continuous cropping, etc.
These activities contribute either solely or combined with other factors to reduce the nutrient profile of a particular soil. It should be noted that certain properties of a particular type of soil make nutrients unavailable for crop use. Properties such as the type of soil structure, soil texture, etc.
The problem of unavailable soil nutrients mandated the need for alternatives needed to incorporate nutrients into the soil to help increase crop yield. One of these alternatives is the use of fertilizers.
Fertilizer is any substance; organic or natural, inorganic or synthetics added to the soil or crops for the intended purpose of growth and development of crops. These substances contain the nutrients needed by the crops to enhance the growth and development of plants. This goal is met in two ways, the traditional one being additives that provide nutrients. The second mode by which some fertilizers act is to enhance the effectiveness of the soil by modifying its water retention and aeration. Many sources of fertilizers exist, both natural and industrially produced.
Fertilizers are categorized into namely:
a. Organic
b. Inorganic
ORGANIC FERTILIZERS
Organic fertilizers are obtained from natural resources. Organic fertilizers are usually (recycled) plant- or animal-derived matter. “Organic fertilizers” can be described those fertilizers with an organic — biologic — origin—that is, fertilizers derived from living or formerly living materials.
Organic fertilizers can also describe commercially available and frequently packaged products that strive to follow the expectations and restrictions adopted by “organic agriculture” (i.e. relates to systems of food and plant production that significantly limit or strictly avoid the use of synthetic fertilizers and pesticides). Fertilizers of an organic origin include animal wastes, plant wastes from agriculture, compost, and treated sewage sludge (wastewater). Beyond manures, animal sources can include products from the slaughter of animals — blood meal, bone meal, feather meal, hides, hoofs, and horns all are typical components.
Organically derived materials available to the industry such as sewage sludge (wastewater) may not be acceptable components of organic farming and gardening, because of factors ranging from residual contaminants to public perception.
INORGANIC FERTILIZERS
Inorganic fertilizers are obtained from synthetic products or elements i.e. from chemical substances. Inorganic fertilizers exclude carbon-containing materials except for urea.
Fertilizers are also categorized on the basis of single (straight) fertilizers or ‘’multi-nutrient’’ (complex) fertilizers.
Single (Straight) fertilizers are classified as substances that provide a single nutrient (e.g., K, P, or N). An example is Ammonium nitrate (NH4NO3)
Complex fertilizers are those that consist of two or more elements. An example is Single superphosphate” (SSP), NPK, calcium ammonium nitrate, etc.
APPLICATION OF FERTILIZERS
Application and application rates of fertilizers depend on the particular type of crop and the result of a soil fertility test carried on a particular soil. A soil fertility test seeks to know the type of nutrient available in selected soils, and also the possible availability of such nutrients. Applying fertilizers on soils without a carrying out a soil test may lead to;
a. Application of excessive nutrients to a soil
b. Waste of resources
c. Application of unnecessary nutrients to the soil.
Fertilizers can be applied in the form of solids or liquid. Whatever form applied depends on the crop and nutritive components of the soil.
SOLID FERTILIZERS
About 90% of fertilizers are applied as solids. The most widely used solid inorganic fertilizers are urea, diammonium phosphate, and potassium chloride. Solid fertilizers are either in granules or powdery forms.
LIQUID FERTILIZERS (FOLIAR FERTILIZER)
Liquid fertilizers comprise anhydrous ammonia, aqueous solutions of ammonia, aqueous solutions of ammonium nitrate or urea. These concentrated products may be diluted with water to form a concentrated liquid fertilizer. The advantages of liquid fertilizer are its more rapid effect and easier coverage.
There are many policy issues surrounding the use of fertilizers especially the abuse of it. Although, the end game is attaining high productivity from crops with a balance of sustainable management of the natural resource base. Fertilizers especially nitrogenous fertilizers during usage contribute greenhouse gases such as carbon dioxide, methane, and nitrous oxide to the atmosphere. The effects can be combined into an equivalent amount of carbon dioxide which further contributes to climate change.
Hence, fertilizers as such should be used judiciously either inorganic or organic forms.
APPENDICES
BY JOSEPH OKPAIRE
