The 5 Chemical and Biological Factors Affecting Crop Production
Agricultural crop production is greatly influenced by soil properties, especially soil type, fertility status, and potential management systems. Today we will be discussing the three (3) chemical characteristics and two (2) biological factors affecting crop production.
1. The Three (3) Chemical Factors of Soil Affecting Crop Production
The soil’s chemical characteristics are of primary importance in crop nutrition. They include;
1. Soil Organic Matter (SOM)
This is the proportion of fresh organic material and humus (partly decomposed and synthesized organic material). These materials exert a profound influence on crop nutrients (through a slow nutrient-release mechanism), soil structure, and cultivation.
Organic matter serves as the soil granulator, being largely responsible for particle aggregation through its efficiency in cohesion and plasticity. it is a rich source of important plant nutrients, particularly nitrogen which is entirely derived from organic matter.
Organic matter influences the color, temperature (by minimizing evaporation from the soil surface), water-holding capacity, water retention, infiltration, pH, and exchangeable capacity of the soil. It is the main source of energy for heterotrophic soil microorganisms, which stimulates their reproduction and growth, thus facilitating their capacity to make the nutrients in soil organic matter (SOM) available to the plants.
Organic materials in the soil are decomposed by primary decomposers (insects, earthworms, fungi) and secondary decomposers (bacteria, fungi). This, in addition to cultivation and bush burning, reduce soil organic matter (SOM) content.
Contrarily, soil organic matter can be maintained by bush fallowing, agro-forestry no-tillage, crop rotation, mixed farming, ground cover management, alley cropping, and incorporation of organic materials into the soil.
Important sources of organic matter are FMW, composts, straw, green manure, animal products, cadavers, garbage, industrial wastes (especially food processing wastes), urban liquid wastes, city refuse, peat (Sphagnum moss, sedge), sawdust, leaf mold, sewage sludge, slurry, sewage effluent, leys, and mulch.
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2. Soil pH
This indicates the degree of acidity or alkalinity of the soil. It is significant in determining the soil’s chemical reactions. Soil acidity (low soil pH) is caused by carbonic acid in rainfall water, organic acids (e.g. humic acids) from the microbial breakdown of organic matter (OM), ammonia from nitrification, and loss of calcium in drainage and crop removal.
Liming helps to correct soil acidity; liming materials include CaCO3, CaO, Ca(OH)2, and Magnesium limestone. Although crop families can occur at pH 5 and below, it is necessary to analyze the soil pH regularly to determine the lime requirement.
3. Available Plant Nutrients
Soil minerals are derived from rock weathering; the primary minerals are derived directly while the secondary minerals are derived from the primary minerals by weathering and synthesis.
Plant nutrients are of three main forms, namely; macro, meso, and micro-nutrients. The macro-nutrients (nitrogen, phosphorus, potassium) are primarily important in crop growth because they are required in large quantities.
The meso-nutrients are calcium, magnesium, and sulphur. The micro-nutrients are required in minute quantities but are also important for the normal growth of some crops and certain physiological processes, namely; enzyme systems, protein and carbohydrate metabolism, nitrogen fixation, chlorophyll formation, pod maturation, and production, growth hormones, and starch forms.
They include; copper, molybdenum, chlorine, boron, manganese, zinc, and iron. Knowledge of the available nutrients not only guides in determining the suitability of the site (soil) for a particular crop but also in formulating soil fertilizer requirements.
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2. The Two (2) Biological Factors of Soil Affecting Crop Production
These are complex, and include the soil fauna and flora;
1. Soil Fauna
This includes both beneficial and damaging animal organisms. Beneficial organisms are those that break down and incorporate crop residues and further aid in water movement and aeration e.g. earthworms.
The damaging organisms consist of the larval stages of click beetle/wireworms, crane fly, chafer grubs, and eelworms/nematodes.
2. Soil Flora
Pathogens such as bacteria, fungi, and viruses are important sources of soil infections in croplands.
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