Productivity of grain cowpea in high phosphorus soils as influenced by nutrient interactions

A field experiment was conducted in a high phosphorus soil in the southern district of Kerala during January to March 2018 to assess the effect of varying levels of P, K and Zn and their interactions on the productivity of grain cowpea. The treatments included two levels of P, three levels of Zn and two levels of K and was laid out in factorial RBD with three replications. The results of the study revealed that significantly higher yield attributes and yield (pod and grain) were realized through foliar application of Zn as ZnSO4 twice @ 0.025% at branching and at flowering, along with 10 kg K2O ha-1 in the high P soil. The yield was 58 per cent higher than the yield at the lower levels of P, K and Zn tried. Economic analysis also revealed higher benefit cost ratio (1.36) for the combination. Phosphorus application may be skipped in the nutrient package for grain cowpea in high soils. Based on grain yields, it could be interpreted that a negative interaction existed between P and Zn and also between Zn and K. The interaction between P and K was not significant.