Effect of sowing date and seed rate on the grain yield and protein content of winter barley

Abstract

SUMMARYAn experiment, carried out over a 5-year period (1984–88) on medium–heavy textured soil at Athy (Ireland), tested the effect of five sowing dates (early September–early December) and four seed rates (c. 100, 150, 200 and 250 kg/ha) on the grain yield and protein content of winter barley (cv. Panda).September-sown plots gave the greatest yields in all years. Plots sown in mid-October and later gave significantly reduced yields. Yield reductions over the 5-year period averaged 15, 24 and 34% for the mid-October, November and December sowing dates, respectively. Significant differences in yield between the smaller and larger seed rates were obtained, with the latter giving the greatest yields at all sowing dates from late September to December. Increasing the seed rate, however, did not compensate for the yield reduction due to delayed sowing. In the early September-sown plots, the higher seed rates gave reduced yields in four of the five years (1984–87) with the opposite result in 1988. In 1988 the early September-sown plots gave greater yields than the late September-sown plots.Regression analysis showed a strong relationship between yield and log(ears/m2) in four of the five years (1984–87) but the relationship was poor in 1988 primarily due to the inexplicably low ear population of the early-sown plots. The inclusion of 1000-grain weight in the model gave a better fit and accounted for a high proportion (62–80%) of the yield variation.The late September sowing date and the higher seed rates gave slightly lower protein levels in four of the five years. There was an inverse relationship between grain yield and protein for the same four years (1984–87).