Ryegrass populations from intensively managed leys: II. Reaction to nitrogen and Poa trivialis L.

Abstract

SUMMARYA Lolium perenne L. population derived from a very productive 6-year-old S.23 ley was compared with that obtained from breeders' seed of S.23. The ryegrasses wqre grown in boxes sown separately, together, and also with Poa trivialis L. Three rates of nitrogen were applied equivalent to 28, 336 and 672 kg N/ha.The results obtained when the two ryegrasses were sown separately differed from those obtained in mixtures. When sown alone, the difference between the two ryegrass populations was small, but the ‘survivor’ ryegrass had a slightly higher yield of dry matter and nitrogen at some sampling dates and fertilizer nitrogen rates. In the mixture of the two ryegrasses, S.23 was higher yielding than the ‘survivor’ population when the equivalent of 672 kg N/ha was applied, but not at lower nitrogen rates.When grown as pure swards, P. trivialis did not yield as much dry matter and nitrogen as L. perenne at the highest N application. In the intergeneric mixtures, the total yield of ryegrass × P. trivialis was not very different from that of ryegrass sown alone. P. trivialis depressed the yield of ryegrass in May and June, particularly when fertilizer N was applied; the reverse effect was recorded later in the year. Total drymatter yield of ryegrass and P. trivialis grown together was similar at the highest fertilizer N rate, but the yield of N was much higher in ryegrass than in P. trivialis.