Phosphorus & molybdeum nutrition in cowpea

Abstract

An investigation was undertaken at the College of Agriculture, Vellayani during the period from April to November 1990 with the objective of assessing the interaction effect between phosphorus and molybdenum on the growth and yield of cowepea. The investigation comprised of an initial pot culture study followed by field experiment. The results of the study indicated that seed coating of molybdenum was better than seed imbibition. Application of phosphorus at the rate of 30.0 kg P2O5/ha increased the height and branching and resulted in maximum LAI, nodule number and weight, chlorophyll content, maximum length of pod, hundred seed weight and highest grain yield of 1152.67 kg/ha. Maximum uptake of nitrogen, phosphorus and molybdenum was recorded at this level. The maximum available nitrogen, phosphorus and potassium content of the soil after the experiment was also recorded at this level. Seed treatment with molybdenum (1.5 and 2.5 kg sodium molybdate/kg of seed) favourably influenced the growth of cowpea by increasing the height of plant, number of branches, LAI, nodulation and chlorophyll content. Yield attributes such as number of pods/plant, pod length, number of seeds/pod and hundred seed weight increased significantly at these levels. Maximum and significant value for grain yield and dry matter production was recorded by the application of molybdenum at the rate of 1.5 g sodium molybdate/kg of seed. Maximum uptake of nitrogen, potassium and molybdenum was noted at the level of 2.5 g sodium molybdate/kg of seed. Seed treatment with 1.5 and 2.5 g sodium molybdate/kg of seed, significantly influenced the available nitrogen, phosphorus and potassium status of the soil after experiment. Combined effect of phosphorus and molybdenum was beneficial in improving the growth and yield of cowpea. Treatment that received 22.5 kg P2O5/ha in conjunction with 1.5 g sodium molybdate/kg of seed recorded maximum value for branching, LAI, chlorophyll content, pods/plant, seeds/pod, pod length, hundred seed weight, harvest index, crude protein content and grain yield of 1287 kg/ha. Highest dry matter production (3455 kg/ha was also recorded at this level of phosphorus and molybdenum. Maximum uptake of nitrogen was recorded by the application of 22.5 kg P2O5/ha in combination with 2.5 g sodium molybdate/kg of seed. The uptake of molybdenum was significantly higher in treatments that received 30.0 kg P2O5/ha and 2.5 g sodium molybdate/kg of seed. Highest phosphorus uptake was recorded by the treatment that received 37.5 kg P2O5/ha in conjunction with 0.5 g sodiuum molybdate/kg of seed. The present investigation revealed that for the variety C-152 a combination of 22.5 kg P2O5/ha with 1.5 g sodium molybdate/kg of seed gave maximum yield and maximum profit. Based on the dose response relationship economic optimum dose for phosphorus was found to be 28 kg P2O5/ha and that of molybdenum 1.37 g sodium molybdate/kg of seed.