INFLUENCE OF SEED QUALITY CHARACTERS ON FIELD EMERGENCE OF GARDEN PEAS (PISUM-SATIVUM L) UNDER VARIOUS SOWING CONDITIONS

The relationship between seed quality characters and field emergence of garden pea seed lots was evaluated in 1988 for 82 seed lots from six cultivars under unirrigated conditions, and in 1989 for 23 seed lots from three cultivars tinder both irrigated and unirrigated conditions on several sowing dates. This study constitutes the most extensive evaluation of the prediction of field emergence in garden peas yet conducted. The favourable 1988 sowing conditions allowed good field emergence. However, low rainfall in November 1989 (unirrigated sowings) and excessive water at the 30 October and 20 December 1989 (irrigated sowings), were associated with reductions in field emergence. The germination test was correlated with field emergence when conditions for sowing were favourable and when low germinating seed lots were included in the analysis. However, when low germinating seed lots (<85%) were excluded, the relationship between germination and field emergence was low and unreliable. Differences in field emergence between seed lots were a reflection of differences in vigour which were detected by the conductivity test. The conductivity test was correlated with field emergence of garden pea seed lots under all but the most favourable sowing conditions. Hollow heart may also be an important component of seed lot performance, particularly under moisture stress. The results of this study raise serious questions about the general applicability of the expected field emergence (EFE) equation which attempts to incorporate all these factors (germination, conductivity, and hollow heart) into a single predictive equation allowing calculation of sowing rates to achieve target plant populations. The conventional equation was particularly weak under conditions giving poor establishment, producing severe over-estimates of actual emergence. Attempts to improve the general equation by multiple linear regression analysis were unsatisfactory because derived equations showed widely different constants between cultivars and for various sowing conditions, and in many instances significant relationships were not obtained.