Response of populations of Lolium perenne cv. S 23 with contrasting rates of dark respiration to nitrogen supply and defoliation regime. 1. Grown as monocultures
1992
Pilbeam, C.J. | Robson, M.J.
Simulated swards of two populations of perennial ryegrass cv. S 23 selected for contrasting rates of mature leaf tissue respiration were grown in a glasshouse. From establishment, the swards were subject to three levels of nitrogen supply (14.5, 32 and 173.5 ppm N) and from the first harvest 7 weeks after sowing, to three cutting frequencies (at intervals of 1, 3, and 6 weeks). Throughout the 18-week experiment, the herbage yield and the mean tiller weight of the slow-respiring population were 10% greater on average than those of the fast-respiring population. Increasing nitrogen supply (from 14.5 to 173.5 ppm N) enhanced the yield advantage of the slower-respiring population--more so under infrequent cutting (from nothing to 22%) than under frequent cutting (from 6 to 13%). Both maximum absolute yields, and the greatest yield advantage of the slow-respiring population over the fast, were achieved when high nitrogen was combined with infrequent defoliation.
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