Optimising potassium fertilizer rates for sustainable maize (Zea mays L.) production on the volcanic soils of Buea, Cameroon

Abstract

Maize (Zea mays L.) production contributes to food security and income generation for many farmers, but productivity is constrained by soil infertility, with potassium (K) deficiency partly accounting for the huge gap between potential and actual yields. This is resolved with K fertilizer input that require appropriate K rates. This study was aimed at determining the optimum K fertilizer rate for maize production on the volcanic soils of Buea in Cameroon. The experiment was setup as randomized complete block design with five K fertilizer rates (0, 30, 60, 90, and 120 kg K ha⁻¹) and four replications. Results reveal increased earthworm abundance at higher K rates (P<0.05). The weight of 1000 maize grains ranged between 320–682 g across K rates, with the lowest in control and highest at 120 kg K ha⁻¹ rate (P<0.05). Maize grain yield ranged between 7.5–11.8 tons ha⁻¹, with the lowest in control and highest in 120 kg K ha⁻¹ rate (P<0.05). Maize yield increased significantly by 17% from control to 30 kg K ha⁻¹, 16% from 30 to 60 kg K ha⁻¹ rates, and only 4% and 6%, respectively, from 60 to 90 and 90 to 120 kg K ha⁻¹ rates (P<0.05). The K use efficiency expressed by the agronomic efficiency decreased significantly by 26% from 30 to 60 kg K ha⁻¹, 24% from 60 to 90 kg K ha⁻¹, and 11% from 90 to 120 kg K ha⁻¹ rates (P<0.05). Similarly, the partial factor productivity decreased significantly by 41% from 30 to 60 kg K ha⁻¹, 31% from 60 to 90 kg K ha⁻¹, and 20% from 90 to 120 kg K ha⁻¹ rates (P<0.05). This decreasing K use efficiency at higher K fertilizer rates is reflected in the decreasing amount of additional maize yield per unit of K fertilizer applied. The income and profitability of K fertilizer input for maize production increased significantly up to 90 kg K ha⁻¹ rate that did not differ from the 120 kg K ha⁻¹ rate (P<0.05). Overall, K fertilization generated additional income that ranged from US$ 3143–4367 ha⁻¹, with the 90 kg K ha⁻¹ rate being the most cost-effective for maize production in the study area.