The effect of interval between harvests and nitrogen application on the proportion and yield of crop fractions in four ryegrass varieties in the first harvest year

Abstract

SUMMARYThe effect of six intervals between harvests and three levels of N application on the proportion and yield of green leaf, dead leaf, ‘stem’ and inflorescence was studied in four ryegrass (Lolium) varieties during a 30-week period in the first harvest year in a field experiment. In one variety, S.23, the ‘stem’ was divided into true stem, leaf sheath, unemerged leaf and unemerged inflorescence.There was a bigger yield of ‘stem’ and a bigger total herbage yield response to doubling the interval between harvests in S.321 and S.22 than in S.23 and S.24.In the absence, but not generally in the presence, of applied N, S.321 outyielded the other varieties. S.24 was particularly responsive to applied N, especially in terms of green leaf yield.There was a large positive effect on yield of doubling the interval (from 3, 4 or 5 weeks to 6, 8 or 10 weeks respectively) during the main period of stem development. During the subsequent period, however, doubling the interval produced very little extra yield of total herbage and reduced green leaf yield substantially.The percentage increase in yield due to the application of N progressively decreased as the interval was increased.Maximum net production of green leaf was obtained by harvesting every 4 or 5 weeks for most of the season, extending to 6 weeks at the end. Harvesting every 3 weeks, by comparison, resulted in a slightly lower annual green leaf yield, but with a distinctly higher proportion of green leaf in the crop.Applied N generally had little effect on the proportion of crop fractions, but reduced the proportion of green leaf and increased that of' stem' in S.23 and S.24 at the August and September harvests.