Effect of drought during pod filling on utilization of water and on growth of cultivars of groundnut ( Arachis hypogaea L.)

Abstract

Cultivars of groundnut ( Arachis hypogaea L.) were grown well watered or well watered except for a period during pod filling when water was withheld. When water was withheld from 84 days after sowing (DAS) to maturity, pod and seed yield was reduced by 30% in the Virginia type cultivars (Virginia Bunch and Robut-33) and by 45% in a Spanish type cultivar, McCubbin. The Virginia type cultivars also extracted water from a greater depth. Robut-33, a cultivar with a high harvest index (HI), produced the greatest yield under both well-watered and water-stressed conditions. In all cultivars, potential pod number (PN) had been almost achieved prior to the start of the period of water deficit. However, low pod number (apparently through abscission of the youngest pods), rather than small pod size, was mainly responsible for the decrease in yield. Part of the yield advantage of Robut-33 lay in initiating a large number of pods prior to the period of water deficit. This greater synchrony of development compared with the other Virginia type cultivar (Virginia Bunch) created a greater sink for assimilate prior to the period of water deficit. During the first 3 weeks of the period of water deficit, Robut-33 also had the highest crop growth rate (CGR) and was thus able to produce the most pod biomass. The characteristics of early and rapid pod growth and high HI were more important in determining yield under this water deficit than was the amount of water extracted from the soil.