Maize and dry bean are the most important food crops that feed over 85% of Kenyan households. However, the productivity of these crops is low due to the high costs of land preparation and weed control, soil infertility and limited soil moisture under the current conventional tillage system of production. A study was carried in Embu County and Kirinyaga County to determine the economic returns of a maize-bean rotation system under different tillage systems and fertilizer regimes. Maize was produced during the long rains under no-till with crop residue retention (NT+CR) and conventional tillage with no crop residue retention (CT-CR) and inorganic fertilizer regimes (NK, NP, PK, NPK, and NPK+CaMgZnBS). Dry bean was planted in the short rains in the same plots where maize under different nutrient management regimes and tillage systems had been grown and harvested. The trial was laid out in a split-plot design with the tillage method as the main plot and fertilizer as sub-plot. Economic performance was assessed using partial budget analysis based on labor data and prices of all inputs used during the production period. Grain yields were reduced by 10% to reflect farmers’ yield levels. Maize and dry bean grains were sold at the prevailing farm gate prices. Results showed that maize-bean rotation was KE 22,718 cheaper under no-till with crop residue retention (NT+CR) than under conventional tillage with no crop residue retention (CT-CR). On average, NT+CR recorded KE 29,569 higher net benefit than CT-CR. The NT+CR tillage recorded a benefit to cost ratio of 3.7 compared to 2.7 recorded under CT-CR tillage system. The NT+CR with NK combined was the most profitable treatment with a benefit to cost ratio of 4.92 for maize and 4.33 for maize-bean rotation system. Based on this research, combination of no-till with crop residue retention has the potential to improve economic status and alleviate poverty among resource-constrained farmers.

The trials were set up in Busia, Embu and Kirinyaga Counties to assess the effect of tillage methods and application of different fertilizer combinations on maize productivity in the lower and upper midland agro-ecological zones of Kenya. Tillage methods were no-tillage (NT) with crop residue retention as mulch (+CR) (NT+CR) and conventional tillage (CT) without crop residue retention on farm surface (-CR) (CT-CR) while fertilizer combinations were NK, NP, PK, NPK, and NPK+CaMgZnBS. The N, P, K, Ca, Mg, Zn, B and S nutrients were applied at the rates of 120, 40, 40, 10, 10, 5 and 26.3 kg ha-1, respectively. The trials were laid in a randomized complete block design with a split-plot arrangement and replicated three times. The results showed that maize leaf area index, plant height, aboveground biomass, crop growth rate, and grain yield were significantly higher under CT-CR than under NT+CR in most of the sites. The CT-CR system out-yielded NT+CR system by 0.3 t ha-1 and 0.6 t ha-1 maize grain in Alupe and Kirinyaga, respectively. However, NT+CR system out-yielded CT-CR system by 0.4 t ha -1 maize grain at Embu. Across all the sites, application of PK and NPK+ZnBMgCaS fertilizer combinations resulted, respectively, in lowest and highest maize shoot biomass, leaf area indices, crop growth rates, plant heights, and grain yields. Based on this result alone, the potential of conservation agriculture in improving yields compared to conventional tillage could not be conclusive despite consistently recording higher soil moisture content across all sites and better yields in Embu. Again, application of a wide range of nutrients may be beneficial to maize production in the study areas as evidenced in the study. Therefore, we recommend multi-season and multi-location trials to comprehensively assess the impact of tillage methods and fertilizer management, particularly in relation to micronutrients.