Effects of lime on soil chemical characteristics and performance of cowpea [Vigna unguiculata (L.) Walp.] on Oxic Haplustalf of a derived savanna ecology of Nigeria

The use of lime in reducing acidity, increasing nodulation and grain yield of field cowpea in Nigeria had not been determined. Hence, field experiments were conducted in 2020 and 2021 cropping seasons at the Landmark University, Omu-Aran, Nigeria. The study was undertaken to evaluate the effects of lime on soil chemical characteristics, growth, nodulation, and yield of cowpea on tropical-derived savanna. The treatments in each year consisted of five levels (0, 2.5, 5.0, 7.5 and 10 t/ha) of lime (CaCO₃). The treatments were arranged in a RCBD and replicated three times. Findings showed that the application of lime improved soil chemical characteristics (pH, N, P, K, Ca, Na, Mg and CEC), growth, nodulation and yield of cowpea compared to the control. Lime application reduced acidity (H+Al³⁺) relative to the control. Lime increased the yield of cowpea from 0 to 2.5 t/ha after which there was a decrease. 2.5 t/ha lime increased pod weight of cowpea relative to the control by 51.2% in 2020 and 48.2% in 2021. 10 t/ha lime reduced pod weight of cowpea relative to the 2.5 t/ha by 237.62% in 2020 and 257.1% in 2021, the reduction in the yield of cowpea can best be explained by the presence of unfavourable soil pH conditions. Therefore, the optimum yield of the cowpea crop was achieved at 2.5 t/ha of lime for the agro ecological zone.