Soil, runoff and nutrient losses under maize and banana cropping systems in Lwiro microcatchment, DRC

This study was carried out with the following objectives i) to characterise the cropping systems; ii) to identify existing soil and water conservation practices in the Lake Kivu basin and iii) to determine the magnitude of soil, runoff and nutrient losses from Maize and Banana based cropping systems in Lwiro micro catchment in the Lake Kivu basin. Characterisation of the cropping systems and the identification of existing soil and water conservation in the Lake Kivu were done using households and key-informants interviews and focus group discussion. Soil, runoff and nutrient losses were determined using runoff plot approach. Instrumentalised runoff plots of 2X15m were installed on maize intercropped with beans and banana gardens. Two soil erosion management practices, namely; Tithonia and contour bunds were tested on Maize intercrop with Beans and mulch for Banana. The experiment included a control practice for each crop. Each treatment and control was replicated four times. Runoff and soil loss were estimated for each rainfall event and aggregated on seasonal basis. Nutrient (N, P and K) losses were estimated per season. The major cropping systems included the banana, maize and cassava based cropping systems. The dominant features are small holding, rainfed and limited inputs. The major soil and water conservation practices used in the Lake Kivu included: mulch under banana; agroforestry, contour bunds, Tithonia and tripsacum under annuals. Results of the long and short rains of the first year of experimentation show that soil and runoff losses did not significantly change with practices and seasons (P>0.05) for both banana and maize based systems. Soil and runoff losses ranged from 15.73 to 32.93 t/ha, and from 168.14 to 322.17 m3; respectively. Nutrient losses varied with practices and seasons (P<0.05) and ranged from 54.68 to 112.34 Kg/ha, 87.7 to 409.4 Kg/ha; 24.5 to 94.22 Kg/ha for K, N and P; respectively. Soil and runoff losses ranged from 8.99 to 20.6 t/ha, and from 85 to 152 m3; respectively. Only K losses changed significantly with season (P<0.05) and ranged from 17.8 to 53.9 Kg/ha under Banana cropping system.