THE CONTRIBUTION OF POD NUMBERS TO FIELD PEA (PISUM-SATIVUM L) YIELDS IN A SHORT GROWING-SEASON ENVIRONMENT

Field pea yields in three sowing-time experiments in 1985, and two experiments in 1986, were split into the following components: pods m-2, seeds pod-1 and average seed size. In both years pods m-2 was the component most strongly correlated with yield, but the others were also positively correlated with yield. Multivariate analysis of variance showed that pods m-2 contributed more than the other components to the site and sowing-time main effects in both years. Seeds pod-1 made no contribution in either year, but average seed size contributed to the site main effect in 1985 and to the sowing time and cultivar main effects in 1986. These results identify pods m-2 as the most responsive component to environmental effects on field pea yield. Pods m-2 was split into stems m-2 and pods stem-1, or into the rate of pod formation and the duration of pod formation. Variation in both stems m-2 and pods stem-1 contributed to differences in pods m-2 in the 1986 experiments. In a comparison of two Derrimut pea crops grown at Merredin in 1984 and 1985, the duration of pod formation and the rate of pod formation both varied. Variation in the rate of pod formation was due to differences in stems m-2 rather than in rates of pod formation stem-1. Pods formed early in the reproductive phase contributed much more to total seed yield than those formed later. This was due to later-formed pods containing fewer seeds and being more likely than early-formed pods to abscise before reaching maturity. The proportion of total seed yield carried on the first three reproductive nodes varied from 64.3% to 94.2%. This proportion was higher in harsher environments. It is suggested that in short growing-season environments increased pod formation rates are desirable to allow compression of the pod formation period, so that fewer pods will be formed late in the reproductive phase when the environment is most limiting. © 1990 CSIRO. All rights reserved.