Establishment of rice determined by interaction between cultivar, sowing depth, and time between irrigation and sowing, in north west Australia

Abstract

The influences of cultivar, depth of sowing, and time between pre-irrigation and sowing, on rice crop establishment were investigated by drilling into moist soil during the dry season in N.W. Australia. As the time between pre-irrigation and sowing increased, median seedling emergence was delayed, and spread of the population's emergence rate and final percentage emergence decreased, particularly for shallow sowing depths. Delayed sowing also resulted in less-vigorous growth of some seedlings. Stomatal conductance was generally lowest in seedlings emerged from shallow depths although leaf-air temperature differentials and measurements of stomatal conductance, usually regarded as reliable indices of plant water status, failed to distinguish between cultivars or sowing treatments. Delaying sowing, with attendant cultivation, for more than 10 days after pre-irrigation resulted in negligible weed populations. The tall, vigorous-growing cultivar Pelde (ex N.S.W.), sown at 6–8 cm depth between 10 and 15 days after pre-irrigation reached sufficient height for permanent flooding within 50 days after sowing. A semi-dwarf cultivar IR661-1-170-1-3 (ex IRRI) proved more sensitive to depth and time of sowing following irrigation; because of its slower growth rate and additional irrigation requirements it was less adapted to this method of establishment.