ENVIRONMENTAL AND AGRONOMIC EFFECTS ON THE GROWTH OF 4 PEANUT CULTIVARS IN A SUBTROPICAL ENVIRONMENT .1. DRY-MATTER ACCUMULATION AND RADIATION USE EFFICIENCY

Four peanut cultivars of Spanish or Virginia botanical type and varyin g time to maturity were grown at a range of plant densities (44 000 to 352 000 plants ha(-1)) and spatial arrangements under irrigated condi tions in sub-tropical southern Queensland, Australia. Total and pod dr y matter production of the very early maturing Spanish cultivar Chico showed strong positive responses to increased plant density up to the highest density tested. Responses were less pronounced for the later m aturing Spanish cultivar McCubbin and were minimal for the Virginia cu ltivars Early Bunch and Mani Pintar. All cultivars were insensitive to spatial arrangements. Accumulation of total dry matter, adjusted for the higher synthesis costs of oil and protein during seed filling, was well correlated to intercepted photosynthetically active radiation (P AR). Much of the variation in dry matter production among cultivars an d plant populations could be accounted for by the effects of differing leaf area duration on cumulative intercepted PAR. Radiation use effic iency was negatively associated with the canopy extinction coefficient (k) within most sowing dates, and also negatively associated with min imum temperature across sowing dates for all cultivars except Mani Pin tar.