Soil Health and Fertility K Boa December 2014

Soil Health and Fertility K. Boa December 2014

Keeping the soil healthy • Conservation agriculture aims to keep the soil alive • Only a living and healthy soil can produce a good crop

What makes a soil sick? • • • “Mining agriculture” Soil erosion Loss of organic matter Compaction of the soil Bare soil exposed to the rain and sun

Effects of a sick soil Bare and productively dead soil Low crop yields. Crops are short & stunted High levels of fertilizers needed.

What is a healthy soil? A healthy soil is a living soil. - It has many soil organisms in it - It is high in organic matter - It is rich in nutrients -The soil surface is always protected by crops or mulch - It is not compacted -It has good internal drainage -- Deep enough for plant roots A HEALTHY SOIL SUPPORTS GOOD CROP GROWTH SO TRY TO KEEP YOUR SOIL HEALTHY

The Key To Success Diversified Rotations No till Cover Crops Soil Health

CA helps to keep soils alive & healthy by its positive effects on • Physical properties • Reduced soil loss • Improved soil structure • Chemical properties • Increased fertility through decomposition of OM • Biological properties • Enhanced soil life

Soil problems that occur in the traditional and conventional systems • • Compaction Surface crusting Erosion Low water holding capacity

Soil fertility management under CA • Soil fertility management in CA is different because reduction in tillage may lead to: – Accumulation of immobile nutrients (P and K) – Reduction of the rate of mineralization of N – Decomposition of residue may lead to immobilization of N – Superficial application of ammonia fertilizers can acidify the soil surface

Practices to avoid accumulation of nutrients in surface layers • • Start with the correct nutrient levels Assess nutrient levels at different soil depths Guard nutrient levels during first 2 – 3 years Apply part of fertilizer in bands

Management of Nitrogen • Three factors that can hinder availability of N for plant in the soil are – Immobilization • Microorganisms take up NO 3 and NH 4 during the initial stage of decomposition so N not immediately available to plants. – Mineralization • Transforming organic nitrogen into NH 4 and later into NO 3 can be absorbed by plants or washed out of profile and lost to plant growth – Volatilization • Broadcasting urea leads to rapid conversion into NH 3. One part of the NH 3 is transformed into NH 4 and stays in the soil solution while other part disappears directly into the air.

Practices to avoid lack of N for plant growth • Include leguminous CCs in your rotations • Application of N before sowing to prevent immobilization • Apply N as band placement during sowing