Medium-term effects of conservation agriculture on soil quality

Inefficient management practices lead to soil organic matter depletion, structure breakdown and increased erosion. This has resulted into low crop yields of sub-Saharan Africa. Conservation agriculture (CA) is being considered as a potential system having the capability of improving soil quality and providing stable yields. A study was therefore conducted, at Chitedze Research Station-Malawi, to evaluate medium term effects of 5 years CA experiment potential in improving soil quality. The results indicated that chemical nutrient build up in CA is gradual and significant differences between treatments were realized from the 4th year of practicing CA. In the 5th year, CA treatments, on average registered 14 and 21% higher in pH and soil organic matter (SOM) respectively than in the common practice. A positive correlation (74%) between soil SOM and pH in the 5th year was observed. CA treatments had a range of 61.2 - 69.4% of the soil particles composed of soil aggregates greater than 2 mm in diameter compared to 30.1% under common practice by the 5th year. In the top 30 cm of the soil, 67 and 17 earthworm’s’ m-2 were recorded in CA and control, respectively. Maize yields were higher in the 5th year as compared to the 1st year. In all the parameters assessed, CA using maize - cowpea rotation treatment gave highest values. Conclusively, CA improves soil quality, especially when legumes are integrated. Key words: Common practice, soil aggregate stability.