Critical potassium deficiency levels for a grass/ legume pasture grown on soils of the subhumid zone of Nigeria

A greenhouse experiment was conducted to determine the critical deficiency levels of potassium (K) in the subhumid zone soils for predicting response of a mixture of Andropogon gayanus and Stylosanthes hamata cv. Verano to K application. Twenty coarse textured soils, having loamy sand to sandy loam textures and with exchangeable K contents ranging from 0.08 to 0.97 cmol/kg, were used. Two rates of K applied were 0 and 80 mg K/kg. Application of K on soils testing less than 0.18 cmol/kg significantly increased the dry matter yields of both Andropogon and stylo tops. Soil K was significantly related to relative yields of Sole Andropogon (r = 0.60∗∗), sole stylo (r = 0.78∗∗∗), and Andropogon/stylo mixture (r = 0.77∗∗∗). There was a high correlation between the K concentration in plant tissue and the relative yields of sole Andropogon (r = 0.68∗∗), sole stylo (r = 0.67∗∗), Andropogon in mixture (r = 0.65∗∗), and stylo in mixture (r = 0.64∗∗). The graphical model of Gate and Nelson indicated the criti...