Agronomic studies on Vigna spp. in South-Eastern Queensland. III. Response to sowing arrangement

The response of two accessions each of black gram (Vigna mungo), adzuki bean (V. angularis) and green gram (V. radiata) to sowing arrangement was evaluated in November, December and January sowings in south-eastern Queensland. Plants were grown in rows 100, 75, 50 and 25 cm apart with a constant within-row density of 20 plants per m, providing population densities of 200, 267, 400 and 800 thousand plants per ha respectively. Dry matter production was generally maximized at the highest population density. However, significant species x sowing arrangement and sowing date x sowing arrangement interaction occurred for seed yield. Yields of black grams were least responsive to population density/sowing date combinations, apparently because of their indeterminate growth habit. The green grams (determinate habit) and adzuki beans (weakly indeterminate) responded to progressively higher population density as sowing was delayed from November to January, reflecting progressively shorter growth duration with later sowing. In each species, yields were generally depressed at the lowest density because vegetative growth was inadequate to achieve complete canopy closure prior to podfilling. Yields were depressed at the highest density for most sowings of the black grams, and the November sowings of the adzuki beans and green grams, because of lodging. It is suggested that sowing date x sowing arrangement interactions might be used to advantage in manipulating sowing date to minimize risk of weather damage in southern Queensland.