Determination of the Optimum Sulphur Fertilizer Rate for Groundnut Production in Selected Soils of Benue State using Sorption Indices

Abstract

Laboratory studies and pot Experiments were carried out to determine the optimum sulphur (S)fertilizer rate for groundnut production in selected soils of Benue state using sorption indices. Surface soil samples (0-20 cm) were collected for sorption studies and pot experiments. The sorption study was carried out by shaking known concentrations of S (0, 20, 40, 60, 80, 100 and 120 mgkg-1) with 5g soil sample. The suspension was filtered and the amount of S in solution determined. The amount of sulphatesorbed was estimated as the difference between equilibrium sulphate concentration and initial sulphate added. Data from the sorption study was fitted into the Langmuir and Freundlich sorption equations. Thereafter a pot experiment was carried out with six levels of solution sulphate concentration to determine the optimum S concentration for yield of groundnut and the amount of sulphur fertilizer required to achieve this concentration in the soil under study. Result show that both soils have the capacity to sorb sulphur. The sorption maxima, buffering capacity and binding energy of the soils under study are 70.66 mgkg-1, 15.81mg kg-1, 0.22 dm3 mg-1 and 117.84 mgkg1, 9.83 mg kg-1,0.08 dm3 kg-1 for Aliade and Daudu soils respectively.The highest yield in Aliade soil was obtained with 6 mg kg-1 S while 12 mg kg-1 S gave the highest yield in Daudu soil. Aliadeand Daudu soils would require 57.41 and 23.69 kg ha-1S respectively to maintain 12 mg/kg and 9mg/kg of S in the soil solution. Hence for groundnut production in Aliade soil, 57.41 kg S ha-1 is recommended while for the Daudu soil, 23.69 kg S ha-1 is recommended.