Herbage yield and nitrogen-fixation in a triple-species mixed sward of white clover, lotus and fescue
1991
Danso, S.K.A. | Curbelo, S. | Labandera, C. | Pastorini, D.
The herbage yield and N2 fixed (based on 15N isotope dilution) in a three-species mixed sward [white clover (Trifolium repens L.), birdsfoot trefoil (Lotus corniculatus L.) and fescue (Festuca arandinacea Schreb)] were evaluated over a 2 yr growth cycle (1986 and 1987). Three harvests were made in each year. The herbage yield of white clover was significantly higher than that of birdsfoot trefoil in only the first two cuts, with birdsfoot trefoil accounting for 86% of the total legume herbage yield in the remaining four harvests. For both legume species the proportion of the aboveground N derived from atmospheric N2 (% Ndfa) fluctuated little over the different harvests. The 2-year averages were, 88 and 91% Ndfa, for white clover and birdsfoot trefoil, respectively. The large fluctuations in the amounts of N2 fixed (Ndfa) across harvests and between the legume species reflected differences in herbage yield. In 1986, both legumes contributed almost equally to the ca 130 kg N ha-1 fixed, compared to 1987, when white clover contributed only 5% of the 46 kg N ha-1 fixed in the last two harvests. The better persistence of birdsfoot trefoil than white clover was therefore not only reflected in higher yields, but also, in greater N2 fixed. Nitrogen fertilization had a differential effect on N2 fixation in the two legumes, with the application of 10 instead of 2 kg N ha-1 decreasing N2 fixation in white clover, but not birdsfoot trefoil.
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