RESPONSE OF GROUNDNUT (Arachis hypogaea L.) TO VARYING RATES OF SULPHUR APPLICATION AND EVALUATION OF SULPHUR EXTRACTANTS IN SELECTED SOILS OF NASARAWA STATE

Abstract

Sulphur (S) deficiency is becoming increasingly important in Nigerian soils, yet information on S status in Nasarawa State remains limited. This study evaluated groundnut (Arachis hypogaea L.) response to varying S rates and assessed S extractants in six soils of Nasarawa State. Laboratory analysis, pot experiments (0, 10, 20, 30, 40 kg S ha−1 as K2SO4), and field observations were conducted using standard procedures. Soils were slightly acidic to neutral (pH 5.82–6.68), with low organic matter (1.34–1.85%) and sandy loam textures. Total S ranged from 15.61–68.83 mg kg−1, while KH2PO4- xtractable S varied from 0.23–1.06 mg kg−1. Groundnut responded significantly (p<0.01) to S application, with optimal rates varying from 10–40 kg S ha−1 depending on soil type and yield parameter. Fresh biomass (43.10–116.15 g pot−1), pod weight (8.85–36.10 g plant−1), pod number (10.00–28.50 plant−1), and seed weight (2.30–7.85 g plant−1) increased with S application. Field yields ranged from 0.49–0.85 t ha−1. Correlation analysis revealed that 0.016 M KH2PO4 extractable S showed the most significant positive correlation with yield parameters (r=0.21–0.36), followed by 0.010 M LiCl, establishing it as the most suitable extractant. The critical S level for groundnut production was established at 0.24 and 0.23 mg kg−1 KH2PO4- extractable S. This study recommends S fertilization for soils with KH2PO4-extractable S below 0.24 and 0.23 mg kg−1, adoption of crop residue management to conserve organic matter, and discouragement of bush burning practices in Nasarawa State.