Tillage Effects on Selected Soil Properties and Rainfed Maize Growth in Upper Kabete Campus, University of Nairobi, Kenya

Abstract

There is a major decline in maize production in Kenya, and this is a serious threat to the national food security reserve; thus, the need for sustainable production approaches Enhancing maize production under rain-fed conditions in arid and semi-arid lands (ASALs) requires efficient tillage and cultivation methods that enable efficient utilization of nutrients and water, as well as conservation of natural resources. Hence this study which was undertaken in the experimental field of Upper Kabete Campus, University of Nairobi for two rainy seasons (long and short rains) aimed to evaluate the effect of different tillage methods on the selected soil properties, maize growth, and yields, as well as to determine the cost-benefit analysis of maize production under selected tillage methods. The soils of the study site were Humic Nitisols. The trial was established on a Randomized Complete Block Design (RCBD) with four replicates that acted as the blocking factor and four treatments comprising Disc Ploughing and Harrowing (DPH), Ripping (R), Jab Planter (JP), and Hand Hoe (HH). Biased randomization of the treatments was done to minimize compaction by tractor wheels under DPH and R during land preparation. The study established variations in the influence of the tillage method on crop and soil parameters according to soil depth, and time as the seasons progressed. Results showed that tillage had a significant (p < 0.05) influence on soil moisture, soil nitrogen, and grain yields during both seasons. Tillage and time of measurement significantly influenced soil moisture during both seasons (<0.001). Ripping recorded the highest moisture values (%) with means of 46.91 and 41.59, with the lowest values under HH (29.55) and DPH (26.95) for the consecutive seasons, respectively. Soil surface roughness (SSR) was significantly affected by tillage during the short rains only with average values (%) of HH (3.11), DPH (2.96), R (2.13), and JP (1.68). In the first season, DPH (2.83) had the highest value while JP (1.5) had the least surface roughness. The trends in crust strength (0-10 cm) were consistent between both seasons, with values ranging from 0.5 to 2.8 MPa. Significant effects of tillage and time of measurement on bulk density were observed during the short rains only, however, JP exhibited the highest bulk densities (Mg m-3) for both seasons with average values of 1.04 and 1.11, respectively. An inverse relationship was observed between bulk density and porosity (%), R (63.29) and DPH (63.45) had the highest total porosity values during long and short rains, respectively. Tillage had no significant effect on saturated hydraulic conductivity which ranged from 3.7 cm/hr to 35 cm/hr for the seasons. Tillage significantly contributed to nitrogen xvi (%) and ripping recorded the highest values during long (0.55) and short (0.56) rains. During both seasons, tillage had insignificant impacts on maize height, leaf area, leaf area index, and biomass yields; while time of measurement had substantial influence on the parameters. Tillage significantly contributed to grain yields during long (P<0.0284) and short (P < 0.01) rains. The average trend of yield (Mg/ha) during long rains was R (5.69)> DPH (5.32)> JP (4.19) > HH (3.96), while the trend during short rains was R (12.73)> DPH (10.04)> HH (9.78)> JP (8.73). Considering the costs of production and market prices during production and at harvest, financial analysis through partial and marginal analyses indicated a 3302% marginal rate of return (MRR) of adopting R over DPH and, 2577% DPH over JP during long rains. In the short rains, adopting R over DPH yielded an MRR of 24828% while 1077% in the case of DPH over HH. Ripping as a form of conservation tillage accrued the most positive effects on soil properties ultimately improving maize grain and is more economically viable. This study recommends ripping for soil conservation, improved yields, and increased income for farmers in Kabete. Additionally, longterm studies are recommended for a better conception of the effects of tillage on soil properties and crop productivity according to regional and site-specific characteristics