Response of vegetable cowpea to phosphorus under varying moisture levels and plant density

Abstract

An experiment was conducted at the Instructional Farm attached to the College of Agriculture, Vellayani in the summer rice fallows during 1994-‘95 to study the response of vegetable cowpea cv. Malika to phosphorus under varying moisture levels and plant density. The experiment was laid out in strip-split plot design with 3 replications. The treatments included three levels each of irrigation and plant density and four levels of phosphorus. The study revealed that the crop responded to irrigation, plant density as well as phosphorus levels. The biometric characters like plant height, number of leaves and branches per plant, earliness in flowering, total DMP and yield attributing characters like number of pods per plant were favourably influenced by giving daily light irrigation of l0mm (farmer1s practice) throughout the crop period. The maximum values for the above said characters were also observed at a plant density level of 16,667 pts/ha (1.0x0.6m) and a phosphorus level of 45kg/ha compared to the other levels. The maximum yield of green pods and haulm was obtained by daily light irrigation with 10mm water and a plant density of 16,667 pts/ha. The crop responded upto 45 kg/ha P2O5 application. The uptake of major nutrients N,P and K by the crop also followed the same trend. But the water-use efficiency was highest for the least freqently irrigated treatment viz. irrigating at 15mm CPE and was found to decrease with increase in the frequency of irrigation. A plant density level of 16,667 pts/ha and a phosphorus level of 45kg/ha also recorded maximum water-use efficiency. Soil moisture extraction pattern showed that less frequent the irrigation, more the percentage of absorbtion from deeper soil layers. A plant density level of 16,667pts/ha as well as a phosphorus level of 45kg/ha also gave maximum absorbtion from top soil layers where as a higher plant density gave maximum absorbtion from the deeper soil layers. The available N, P and K contents of the soil after the experiment indicated a decrease in the soil nutrient status with an increase in the moisture level of the soil. The highest nutrient status was also noted with a density level of 16,667 pts/ha and a phosphorus level of 45kg/ha. The results of economic analysis revealed that the net income and benefit-cost ratio was maximum by irrigating the crop at 10mm CPE, at a plant density of 16,667 pts/ha and a phosphorus level of 45kg/ha.