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.

In this study, the effects of two traditional, three reduced and a zero tillage methods applied for nine years on GEA and PMN were determined and compared. The study, initiated in 2006 as randomized block design, includes a total of 18 plots with 3 replications for 6 different soil tillage systems. In the study, six different soil tillage methods are applied, namely conventional tillage with stubbles (CT-1), conventional tillage with stubbles burned (CT-2), reduced tillage with heavy disc harrow (RT-1), reduced tillage with rototiller (RT-2), reduced tillage with heavy disc harrow (RT-3) and no tillage (NT). Winter wheat was grown as the main crop every year or corn and soybean was grown following the harvest of wheat (second crop) every other year. Differentiation of tillage systems led to a significant variation in GEA and PMN concentrations. The GEA concentration, which increased significantly with the decrease in tillage density, varied between 44.68 mg PNP kg-1 h-1 (CT-2) and 207.66 mg PNP kg-1 h-1 (STI). However, the trend determined in GEA could not be detected in PMN. Although PMN concentration was significantly higher in soils under NT, it was included in the same statistical group with RT-1 for PMN concentrations. Higher PMN concentration in no till soils can be possibly related to the non-disturbance of soil structure. The results of study revealed that reduced and no tillage systems are extremely necessary to increase the quality of soils in the region.