Enhancing Sorghum Productivity in Acidic Soils Through Lime–Fertilizer Synergism: Agronomic, Economic, and Composite Performance Analysis

Abstract

Sorghum productivity in Western Kenya is severely constrained by acidic soils, particularly Ferralsols and Acrisols prone to aluminum toxicity and phosphorus fixation. This study assessed the performance of lime-integrated fertilizer treatments under smallholder conditions using a randomized complete block design across three sites. Sorghum grain yield (SGY), agronomic efficiency (AE), nutrient uptake efficiency (NUE), and gross margin (GM) were measured alongside the formulation of a composite Performance Index (PI) designed to simulate both physiological and economic effects. We developed a composite Performance Index to integrate agronomic and economic outcomes, enabling balanced evaluation of lime–fertilizer strategies across acid-prone sites. The PI incorporated weighting scenarios reflecting equal and smallholder-adjusted preferences. Results showed that lime enhanced AE (up to 55%), NUE (up to 34.6%), and SGY ≥ 1.8 t ha⁻¹ across sites, with intermediate fertilizer rates yielding superior performance. GM exceeding $450 ha⁻¹ and benefit–cost ratios over 2.0, demonstrating strong economic viability, Lime + N37.5P13 consistently outperformed other treatments, offering agronomic–economic balance and robust PI ranking across sensitivity models. Radar and contour plots identified optimal combinations and revealed trade-offs between efficiency and yield. These findings support lime as a foundational input rather than a supplemental one, and advocate for context-driven ISFM strategies aligned with smallholder realities. The PI framework offers a flexible and empirically grounded tool for sustainable intensification decisions in acid soil systems.