High yields are realised when crops are grown on fertile soils. Soil is said to be fertile if it is able to supply essential plant nutrients in adequate amounts.
What are the qualities of fertile soil?
Fertile soil comprises medium size soil particles, high humus containing decaying plant and animal material, high water holding capacity and high activity of useful living organisms like earthworms and insects.
How can soil fertility be restored?
Resting land and fallowing with nitrogen fixing crops like tephosia, mucuna and canavalia can be successful measures of restoring soil fertility.
- Crop rotation. This includes a resting phase during which grass and legume hey is allowed to grow.
- Afforestation: Trees are planted on sloping land to reduce wind and water erosion.
- Mulching: Well-laid mulch acts as a barrier and thus prevents soil and water from being carried down the slope.
- Manuring: Use organic manure such as kraal manure, compost and green manure restores and maintains soil fertility.
- Drainage: Water-logged soils such as clay soils can become productive if water is drained off.
- Water holding capacity of sandy soils can be improved by adding organic manure.
Others are soil and water conservation measures. These include use of trenches, grass strips, sunken beds, contour farming and growing cover crops.