LIMITATIONS TO SEED YIELD IN SHORT-DURATION PIGEONPEA UNDER WATER-STRESS

Yield components were determined for two short-duration pigeonpea [Caj anus cajan (L.) Millsp.] cultivars, ICPL 87 and ICPL 151, in response to terminal drought stress with three partial flower/pod removal or fo ur foliar fertilization treatments applied from the time of full flowe ring. Flower/pod removal treatments comprised a control with no flower /pod removal, lower-plant flower and pod removal at full flowering and 18 days later (EL), allowing pods to develop only on the top-3 nodes of the main stem, and flower/pod removal 18 days after full flowering only (L). The EL and L treatments were applied to ICPL 87 and only the EL treatment to ICPL 151. Seed yield of the top-3 nodes was increased by the EL treatment for both cultivars under rainfed and irrigated co nditions, but was not significantly affected by the L treatment. With flower/pod removal, increased yields of the top-3 nodes were due to in creases in the pod density and/or the seed size, with little change in the number of seeds pod-1. Foliar fertilization of cultivar ICPL 87 w ith solutions containing N, P, K and S in similar proportions to those found in developing seeds at 20 and 40 kg N ha-1, had no significant effects on yield or yield components under either soil moisture condit ion. Factors within the plant during early reproductive growth appear to limit seed yield under both soil moisture conditions, and reproduct ive sink capacity and nutrient (N, P, K and S) supply, apparently, are not limiting. Such information on plant factors limiting yield under water stress conditions allows for a better understanding of drought r esistance mechanism(s) for short-duration pigeonpea.