Soil physical properties and maize productivity under different tillage methods in the Central Highlands of Kenya

Résumé

Background. Inappropriate tillage methods are one of the leading causes of land degradation which threatens food security in most sub-Saharan countries, especially given that most agriculture is rain-fed. Thus, production approaches to address this challenge need to be holistic, not only to improve crop production but also to enhance soil health and conserve water sustainably. Objective. To evaluate the effects of different tillage methods on soil properties and thus the impact on crop performance using maize as the test crop. Methodology. The study was done at the Upper Kabete Campus, University of Nairobi, during the 2021 long and short rainy seasons. The soils at the study site are Humic Nitisols. The trial used a Randomized Complete Block Design (RCBD) with four replicates and four treatments: Disc Ploughing and Harrowing (DPH), Ripping (R), Jab Planting (JP), and Hand-Hoeing (HH). Soil physical properties and crop performance indicators were monitored throughout the seasons. Results. Results indicated that tillage significantly (p<0.05) influenced soil moisture and grain yields in both seasons. Average moisture levels (%) were 46.91 (R)>31.41 (DPH)>29.60 (JP)>29.55 (HH) during long-rains and 41.59 (R)>28.38 (JP)>28.32 (HH)>26.95 (DPH) during short-rains. Soil surface roughness was significantly affected by tillage during SR, with average values (%) of 3.11 (HH), 2.96 (DPH), 2.13 (R), and 1.68 (JP). Crust strength trends were consistent across seasons, JP>R>DPH>HH, and values ranged from 0.5 to 2.8 MPa. Bulk density (Mg m⁻³) during SR averaged 1.11 (JP)>1.03 (HH)>1.02 (R)>0.97 (DPH), with tillage significantly influencing the values. Porosity, inversely related to bulk density, average values (%) were 63.45(DPH)>61.61 (R)>61.31 (HH)>58.11 (JP)) in SR. Tillage did not significantly affect saturated hydraulic conductivity. Tillage also had no significant effects on maize height, leaf area, leaf area index, and biomass yields. Average grain yield (Mg/ha) trends during long-rains were 5.69 (R)>5.32 (DPH)>4.19 (JP)>3.96 (HH), and during short-rains, 12.73 (R)>10.04 (DPH)>9.78 (HH)>8.73 (JP). Implications. The findings of this study establish that minimum tillage can improve soil quality and crop production. Conclusion. Ripping yielded the most positive effects on soil properties and crop yields and is recommended for sustainable soil management and maize productivity in the Central Highlands of Kenya and similar agroecological zones.

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