LEARNING OBJECTIVES
By the end of this lesson, you should be able to:
- Explain the meaning of soil fertility and the characteristics of a fertile soil.
- Describe how soil loses fertility and methods of maintaining soil fertility.
SOIL FERTILITY
Soil fertility refers to the ability or potential of a soil to provide crops with the required nutrients and in correct amount and proportion for sustained high yield.
Characteristics of a fertile soil
A fertile soil has the following characteristics:
- It has high levels of plant nutrients in their suitable proportions and amounts.
- It has good water-holding capacity.
- It has an appropriate soil pH.
- It is properly aerated and drained.
- It has good depth.
- It is free from pests and diseases.
- It has good structure and texture.
How soil loses fertility
Soil may lose its fertility through the following ways;
- Soil erosion, where the top fertile soil is carried away by agents of erosion like wind and water.
- Denitrification of nitrates.
- Leaching, whereby nutrients are carried to lower layers where plant roots cannot reach.
- Uptake of nutrients by weeds.
- Changes in soil pH, which makes some nutrients unavailable to crops.
- Fixation of nutrients into insoluble forms.
- Continuous cropping, which leads to loss of soil nutrients through uptake by plants.
- Burning of land, thus killing micro-organisms in the soil and destroying organic matter.
- Development of hardpans and soil capping, which prevents free circulation of air in the soil.
- Accumulation of salts.
- Mono-cropping, which leads to depletion of one type of plant nutrients and buildup of pests and diseases.
Methods of maintaining soil fertility
Soil fertility can be maintained through the following methods:
- Adding manure to the soil to enrich it with more nutrients.
- Practicing crop rotation to ensure balanced nutrient use.
- Using appropriate tillage, for instance minimum tillage.
- Controlling soil erosion.
- By irrigation, thus increasing the availability and uptake of plant nutrients and reclaim saline soils.
- By weeding to reduce competition for nutrients.
- Regulating soil pH through liming.
- Through mulching, this improves soil fertility by preventing loss of moisture, controlling soil erosion, suppressing the growth of weeds, releasing plant nutrients on decay and its water retention capacity.
- By practicing inter cropping preferably with legumes to enhance nitrogen fixation.
