Lesson 3: Linking to Components of Soil Fertility

There are different ways to measure soil fertility depending on what type of crop you are planting. Generally, fertility is measured by looking at the chemical, biological, and physical properties of the soil. 

• Chemical properties – this refers to the relative acidity and alkalinity of the soil, total soil organic matter, and the level of active organic matter. 

• Biological properties – this refers to the microbial biomass and variety of microorganisms.

• Physical properties – this refers to soil texture, soil structure, depth of soil, and rooting and water-holding capacity.

These three properties of soil affect each other. For example, adding plant residues can improve the nutrient and water-holding capacity of soil, which can alter the chemical properties, and in turn make the environment more conducive to a high level and variety of organisms in the soil. 

It is likely that the physical properties of the soil has the most impact on soil organisms. Soil organisms have a greater effect on the chemistry of the soil. The physical and chemical properties of soil are linked by processes such as the absorption of nutrients and the movement of nutrients through the soil. 

As crops grow, the amount of organic matter in the soil decreases, so organic materials should be added to keep the soil fertile. Sources of organic material include compost, well-rotted animal manure, green manure crops, effective microorganisms, and mulch.