Influence of genotype, seed size, and seedling density on the winter herbage production of subterranean clover (Trifolium subterraneum L.) lines and cultivars

Abstract

An important factor often limiting stocking rates in cool-temperate environments is winter growth. Field trials were carried out to test the hypothesis that if the effect of seedling density and seed size is accounted for, then significant differences in winter production between cultivars and lines of subterranean clover can be detected. Winter production of second-year swards was measured on 11 lines of Trifolium subterraneum variety subterraneum and four crossbreds variety yanninicum from the National Subterranean Clover Improvement Programme (NSCIP), together with 15 commercial cultivars. Three sites were sown in autumn 1987 at Cressy (Midlands), Bridport (North East Coast), and Swansea (East Coast) in Tasmania. On average, the most productive line in winter was CPI 89820D, with a clover dry matter (DM) production of 964 kg/ha. The commercial cultivars Karridale and Enfield averaged 876 and 818 kg DM/ ha. Seedling density accounted for 45, 69, and 73% of the variation in winter production at Bridport, Cressy, and Swansea respectively; however, large differences in winter production between genotypes growing at similar densities were observed. For instance at Cressy, Enfield produced 2½ times more forage than Larisa, and at Bridport 89860D and 89774F were twice as productive as 89816F. Spring yield was a function of maturity rating and was not affected by seedling density. Winter production was not related to maturity. The results suggest that breeding and selecting for winter growth, in addition to high seed yield and regeneration, will improve subterranean clover winter production in a cool-temperate environment.

Keywords:

• Trifolium subterraneum
• subterranean clover
• winter production
• regeneration
• cool-temperate environment