EFFECTS OF SEED VIGOR AND DORMANCY ON FIELD EMERGENCE, DEVELOPMENT AND GRAIN-YIELD OF WINTER-WHEAT (TRITICUM-AESTIVUM L) AND WINTER BARLEY (HORDEUM-VULGARE L)

Field trials with dormant and artificially aged non dormant seed of four winter barley varieties and three varieties of winter wheat were performed in two years. Effects on field emergence, plant development and grain yield were observed.-Artificial ageing of seed lots effected the mean germination time relatively more than the laboratory germination percentage. Thus all seed lots used in the field trial were of commercial standard with respect to laboratory germination percentage. Increased mean germination time exclusively due to seed dormancy at the time of sowing effected neither field emergence nor grain yield. Increase in mean germination time due to poor seed vigour resulted in a significant grain yield loss. The largest effect was found in winter wheat where an average relative increase in mean germination time of 71% from 2.1 days to 3.6 days with a corresponding decrease in laboratory germination percentage from 99% to 95% resulted in a relative loss in grain yield of 16%. For the wheat varieties an overall significant negative correlation between mean germination time of non dormant seed lots and the number of field emerged seedlings was found. Increasing sowing rates of low vigour seed lots did not secure optimal grain yield.