EVALUATION OF IMPACTS OF INTEGRATED LIME AND FERTILIZER APPLICATION ON SELECTED SOIL CHEMICAL PROPERTIES AND SORGHUM PRODUCTIVITY IN ACID SOILS OF WESTERN KENYA

Abstract

This research assessed sustainable strategies aimed at enhancing soil fertility and sorghum production in the acidic soils of western Kenya. Microdosing trials were

carried out in Kakamega and Siaya. These were executed under two conditions: lime- treated (4 t ha−1) and untreated (0 t ha−1), and were factorially combined with varying

application rates of nitrogen (18.8, 37.5, and 75 kg ha−1) and phosphorus (6.5, 13, and 26 kg ha−1). The study employed a randomized complete block design (RCBD) with treatments analyzed using ANOVA, followed by Tukey’s HSD for mean separation. Results revealed liming significantly increased soil pH (from 4.50 to 6.19), reduced exchangeable Al, and improved grain N and P uptake. SOC rose across sites, with lime– fertilizer treatments showing strong positive trends. The application of lime significantly (p < 0.001) enhanced both sorghum biomass and grain yield by increasing soil pH, which in turn mitigated Al toxicity, improved root access to P, and promoted N assimilation. Micro-doses of N and P fertilizers were superior to recommended doses in grain and biomass yield, agronomic efficiency (AE), and harvest index (HI). Nutrient uptake efficiency ranged from 21.91–34.54%, with the maximum at N18.8P6.5. Increasing doses of fertilizer reduced NUE and AE. Combining 4 t ha−1 lime with N75P26 fertilizer maintained the highest gross margins and benefit–cost ratios (BCR > 2.0; p < 0.001) at sites and seasons. Seasonal differences affected profitability, with 2018- LR performing better than other years. The combined application of lime and fertilizer yielded the highest economic efficiency among the treatment options, with lime + N37.5P13 treatment proving to be the most economically viable option among the smallholder farmers. The integration of site-specific fertility management with the conventional application of lime (4 t ha−1), along with microdoses of N and P fertilizers, has the potential to rehabilitate acid-degraded soils in western Kenya, thereby significantly improving sorghum productivity and increasing farmers' incomes.