Integrated Effects of Lime and Fertilizer Applications on Soil Properties and Sorghum Performance in Acidic Soils of Western Kenya

Abstract

Acidic soils cover significant portions of agricultural land in tropical regions, particularly in sub-Saharan Africa, where soil acidity limits crop productivity through multiple mechanisms, including aluminum toxicity, phosphorus fixation, and impaired nutrient cycling. In Western Kenya, where smallholder farmers predominantly grow sorghum (Sorghum bicolor L.) as a staple crop, these soil constraints contribute to chronic yield gaps. While agricultural lime and mineral fertilizers are recognized solutions for soil acidity amelioration, their site-specific interactions and comprehensive effects on both soil health and crop performance remain insufficiently documented. This study evaluated the effects of liming and nutrient microdosing on soil chemical properties and sorghum (Sorghum bicolor (L.) Moench) productivity in the acidic soils of Western Kenya, using factorial field trials conducted in Kakamega and Siaya counties. Treatments combined two lime levels (0 and 4 t ha⁻¹) with varying nitrogen (0, 18.8, 37.5, and 75 kg N ha⁻¹) and phosphorus (0, 6.5, 13, and 26 kg P ha⁻¹) rates. Application of 4 t ha⁻¹ lime significantly (p ≤ 0.05) improved soil chemical properties, increasing soil pH by 20–27%, reducing exchangeable aluminum by 56–89%, enhancing available phosphorus by up to 57%, and increasing total nitrogen by 8–17%. Additionally, soil organic carbon was significantly elevated (p < 0.001), with the greatest improvement (39%) observed in Siaya. Microdosing at 37.5 kg N and 13 kg P ha⁻¹ (N37.5P13) produced the highest sorghum biomass and grain yield responses, with biomass yield increasing by 62–69% and grain yield significantly enhanced at Kakamega (p < 0.001). Grain yield over the control rose by 73%, while agronomic efficiency peaked at 24.1 kg grain kg⁻¹ nutrient at Siaya. Nutrient uptake also improved under liming and optimal fertilization, with stover nitrogen uptake increasing by 55% at Kakamega and grain phosphorus uptake rising by 44% at Siaya Site 2 (p < 0.05). These findings demonstrate that integrating site-specific liming with nutrient microdosing can substantially improve soil fertility and sorghum productivity in acid-degraded soils of Western Kenya.