Soil management strategies enhanced crop yield, soil moisture, and water productivity in Nitisols of the Upper Eastern Kenya

Low soil moisture and declining crop yield caused by erratic rainfall, and poor soil management practises contribute to the continuous decrease in water productivity. We sought to assess the effects of the selected soil management strategies on crop yield, soil moisture, and water productivity in the Nitisols. We carried out the study in Chuka, Tharaka-Nithi County, and Kandara, Murang'a County. The experiment was laid in a split-plot design. Minimum and conventional tillage were the main treatments, while soil fertility inputs were the sub-treatments. The soil fertility inputs included sole mineral fertilizer, mineral fertilizer plus animal manure, mineral fertilizer plus crop residue, Tithonia diversifolia plus phosphate rock (Minjingu), sole animal manure intercropped with Dolichos Lablab L.. Maize grain, stover yield, soil moisture, and water productivity significantly increased by 6–22, 10, and 31–33% under conventional tillage than minimum tillage. Mineral fertilizer with or without organic inputs and with or without crop residue mulch significantly (p>0.0002) enhanced maize grain yield by 96 – 729% and stover yield by 79 -276% compared to the control in the two sites during the experimental period. Soil fertility inputs significantly increased soil moisture at 0–20 cm depth at the Chuka site by 10 - 40%. Water productivity was significantly (p > 0.0001) improved under mineral fertilizer with or without organic inputs and with or without crop residue mulch by 46 - 279% in both sites. Generally, the combination of organic and inorganic resources plus crop residue mulch enhanced soil water productivity irrespective of the tillage method. Their use should be encouraged for improved water productivity. However, tillage effects on crop yield, soil moisture, and water productivity should be investigated under long-term conditions.