Beneficial effects of microbes in nutrient recycling in cropping systems of Malawi

Abstract

The major constraint to agricultural production in Malawi is soil fertility decline. The beneficial effects of microbes in the soil, in sustaining soil productivity are promoted in the country through the introduction of organic matter technologies. However, the effect of using maize stover on long term soil fertility improvement has not been assessed in the country. Maize stover is the most abundant crop residue in different cropping systems and could sustain soil productivity if properly utilised. Research was initiated to evaluate the long-term effects of incorporating or removing maize stovers on soil fertility, microbial activities and crop yields at two sites. Mulching significantly increased grain yield in the third season at both sites although yield reduction was experienced in the first and second season due to mulching. Mulching and nitrogen application enhanced microbial activities, which is essential in nutrient recycling. Mulching significantly reduced soil pH, available phosphorus and exchangeable potassium in the first and second seasons. However, mulching increased soil pH, soil organic matter, exchangeable potassium, calcium and available phosphorus in the third and fourth seasons and maize yields significantly increased with mulching in third and fourth seasons. The results show that boxed ridging and maize stover mulching is sustainable because soil microbial activities and soil productivity improved in long term. Soil nutrient immobilisation was not observed in the third and fourth seasons indicating that microbes play a very important role in nutrient recycling in farmers cropping systems.


J. Trop. Microbiol Vol.1 2002: 47-53