Effect of combinations of land clearing and soil management practices on microbial biomass

Abstract

In a non-fertilizer agriculture of Uganda practiced on low-CEC soils microbial biomass and activities may be affected by and clearing, tillage and soil management practiced in the country. A three-year experiment was conducted at Makerere University Research Institute, Kabanyolo to determine microbial biomass in soil under four different combinations of land clearing, tillage and soil management practices. Also to evaluate changes of microbial mass in soil under intensive cropping for three years on a piece of land fallowed for over I0 years. Four treatment combinations were applied: (i) semi mechanized with slash and burn clearing return crop residues (ii) mechanised with bull doze clearing, fertilization and return of crop residue (iii) semi mechanised with no burning and returning of crop residue (iv) traditional with slash and burning of bush and removal for crop residue. During three years, maize (Zea mays) and beans (Phaseolus vulgaris) were grown in a seasonal sequence of maize during long rains and beans for short rains per year. Soil samples were taken at 0 - 20 cm depth from each treatment plot at pre-clearing, after 1 year, 2 years and 3 years of cropping. Using Chloroform fumigation incubation method soil samples microbial biomoss (C and N) was determined. Also the portions of samples were analysed for total carbon. Results showed that MFR treatment greatly favoured the microbial activities than the rest of the treatments. And the TRD, which involved removal of crop residues from the plots, is an unhealthy practice for microorganisms