EFFECT OF TIMING AND INTENSITY OF DROUGHT ON THE GROWTH AND YIELD OF FIELD PEAS (PISUM-SATIVUM L)

The response of field peas (Pisum sativum L.) to timing and intensity of drought was determined in an experiment in a mobile rainshelter, wh ich excluded rainfall during growth of the crop. Twelve irrigation tre atments subjected the crops to drought of varying duration at differen t stages during plant growth. Before and after the drought, the crops were fully irrigated. Pea seed yield decreased linearly as the maximum potential soil moisture deficit (D-pmax) experienced during the growt h of the crop increased from 49 to 323 mm. The timing of D-pmax did no t affect the decline in pea seed yield, but did affect the total dry m atter (DM) produced by the crop. If D-pmax occurred before flowering, radiation interception and total DM yield were reduced more than if D- pmax occurred after flowering. However, this total yield reduction was completely offset by an increase in individual pea weight and consequ ently an increased harvest index. Pea seed yield was closely related t o pod number per unit area, which was also strongly related to water s tress. The number of peas per pod was unaffected by water stress.