Effects of conservation agriculture on bean and maize yield, soil properties and water productivity in Bugesera District, Rwanda
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Land degradation is a major threat to food security and natural resources management in Rwanda as well as in SSA. The major objective of this study was to evaluate the effects of tillage methods, residue management and fertilizer application on bean and maize yield, soil properties and water productivity in Bugesera District, Rwanda. Experiment was established in Bugesera district located in Eastern province of Rwanda. The experimental design was Split Plot with 4 replications. The main plots were conventional tillage (CT) and no tillage (NT), while sub plots were control, Residues applied (RA), RA with inorganic fertilizers and sole inorganic fertilizers (IF). Experiment was carried out for two seasons; A2014 and B 2014.Soil properties assessed were Organic carbon, total Nitrogen, CEC, available P and soil pH. Calibrated parameterized and validated APSIM model was used for scenario analysis to assess the long term effect of Residues application on maize yield, water productivity and organic carbon with a scenario of 10% reduced rainfall. Data were subjected to analysis of variance (ANOVA) using Genstat Dicovery Edition 3. Residues application with inorganic fertilizers had 103% higher bean grain yield than the control, conventional tillage had 23% higher bean grain yield than no tillage. Residues application increased maize grain and biomass yield by 68% in conventional tillage while in no tillage, inorganic fertilizers treatment had higher maize grain and biomass. Residues application resulted in increase of organic carbon Available P was significantly increased in RA and in residues applied with inorganic fertilizers. The increase in soil pH was observed in inorganic fertilizers treatment and in, respectively, for conventional and no tillage. Residues applied with inorganic fertilizers had 103% higher bean water productivity and 78% higher maize water productivity than the control. Conventional tillage had 23% higher beans water productivity compared to no tillage. Long term simulation of the effect of residues and fertilizer shows no significant effect of reduced rainfall on maize productivity. However residues applied with inorganic fertilizers had higher grain yield, higher maize water productivity and 10.6% higher organic carbon than the control. The study concluded that the combination of Residue application and inorganic fertilizers should be considered as the engine for the success of conservation agriculture implementation in Rwanda.