Nitrogen management for grain cowpea (Vigna unguiculata (L.) Walp.) in summer rice fallows

Abstract

A field experiment was conducted at the College of Agriculture, Vellayani during the summer season of 1983-84 to study the response of two varieties of cowpea to different nitrogen management conditions. Various combinations of 5,10,20 or 30 kg N/ha basal, 0,5 or 10 kg N/ha top dressing as foliar spray at flowering, immediately after fertilization of early flowers and mid pod-fill stage as major treatments and two varieties (Kanakamony and Krishnamony) as minor treatments were tried in a split plot design with three replications. The study revealed the favourable influence of higher amounts of nitrogen on growth characters lika plant height, leaf number, number of branches per plant and number of nodules at flowering. Yield components such as number of pods per penduncle, pods per plant, seeds per plant and percentage of podset increased significantly by foliar application of nitrogen at different stages of the reproductive phase. The highest grain yield of 476 kg/ha was obtained from plants receiving 20 kg N/ha basal plus 10 kg N/ha applied to foliage at mid pod-fill stage. The number of seeds per pod and 100 seed weight were not influenced by the Various nitrogen levels tried. Harvest index and protein content of grain were enhanced by application of nitrogen as basal plus foliar sprays. The nitrogen content in plant parts were increased with increasing amounts of nitrogen. Foliar application of nitrogen at flowering or mid pod-fill stage increased the leaf nitrogen concentration The total nitrogen content available P2O5 and available K2O contents of soil influenced by the treatments. The higher level of nitrogen invariably led to higher values of total nitrogen in soil, available and available K2O after the crop harvest. The greatest profit of Rs 1661.85 was obtained from plants receiving 20 kg N/ha basal plus 10 kg N/ha as foliar spray at mid pod-fill stage (T12) The study indicated that application of 20 kg N/ha basal when supplemented v/ith 10 kg N/ha as foliar spray at mid pod-fill stage of the crop could give higher grain yields and profits.