Significance of Plant Residue Management under the Matengo Pit System in Mbinga District, Southern Tanzania

Abstract

The Matengo pit system is one of the indigenous farming systems implemented in Tanzania. It is characterized by a two-year rotation with a short fallow period in the first year. After the fallow period, weeds are slashed, arranged in a lattice shape and buried in ridges. Kidney bean (Phaseolus vulgaris L.) and maize (Zea ways L.) are planted in the first and the second years, respectively. In this study, a litterbag experiment and soil analyses were conducted in a farm under this system to evaluate the nutrient content and the rate of decomposition of plant residues buried in ridges and to analyze the effect of residue management on the topsoil properties. Three types of weeds (Pteridium aquilium L., Imperata cylindrica L., Nidorella resedifolia L.) and maize were put in the litterbags, buried in new ridges and collected after 108 and 132 days. The remaining weight and nutrient content were then determined. The results indicated that the initial content of nutrients was high for the leaves of P. aquiridium and N. resedifolia and low for maize stalks, and that nutrient-rich residues released nitrogen faster. Plant residues were almost completely decomposed in the first year, based on a single exponential model. Moreover the results of soil analyses suggested that the fertility and the depth of the topsoil were maintained over a long neriod of time by the formation of large ridges with plant residues buried inside.