Agronomic studies on Vigna spp. in south-eastern Queensland. II. Vegetative and reproductive response of cultivars to sowing date

Abstract

Vegetative and reproductive growth of 16 cultivars from four Vigna spp. (V. radiata, green gram; V. mungo, black gram; V. angularis, adzuki bean; and V. umbellata, rice bean) were studied over a range of sowing dates at Lawes in south-eastern Queensland.

Seed yield and total dry matter (DM) at maturity were highest in the black grams, and lowest in the adzuki beans. Within species, vegetative development was generally higher in the later-maturing cultivars, but the same was not true for seed yield. Harvest index was negatively associated with cultivar maturity in the grams and adzuki beans.

All cultivars showed substantial response to sowing date, with highest total DM and seed yield for December sowings. Delayed sowings reduced growth such that for late February sowings, total DM at maturity and seed yields were generally less than one-tenth of the maximum. Harvest index revealed an optimum type response to sowing date, with highest values for late December/early January sowings.

Phenological response per se was not a useful predictor of the effect of sowing date on yield or total DM for any of the 16 cultivars, since in all cases growth rates varied substantially with sowing date, apparently in response to temperature. The linear form of the Arrhenius equation relating mean growth rate and mean prevailing temperature provided an excellent description of the response of both yield and total DM accumulation rates over sowing dates for all cultivars. Among cultivars, there was a significant correlation between the slope of the Arrhenius plots (k values) for seed yield and total DM accumulation, implying similar relative temperature sensitivity for both growth processes.

For the 16 cultivars tested, the absolute magnitude of the k values for both seed yield and total DM accumulation was significantly negatively correlated with the latitude from which the cultivars were introduced, which implied greater temperature sensitivity for cultivars from the tropics.

Some implications of these responses on cultivar adaptation and cultural practices are discussed.