Quantifying the effect of nitrogen fertilizer applications in spring on white clover content in perennial ryegrass lolium perenne cultivar barlenna white clover trifolium repens swards

Laidlaw, A.S.

Grass and Forage Science 39(4): 317-322

1984


ISSN/ISBN: 0142-5242
Accession: 006239136

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Abstract
Data are presented for the 4th (1979) and 5th (1980) harvest years of a trial in which 4 levels of N fertilizer (0, 30, 60 and 90 kg N ha-1) were applied each spring to swards with grass (perennial ryegrass cv. Barlenna) and each 1 of 4 cultivars of white clover (Blanca, Sabeda, Olwen and S100) or grass alone. Results from the 1st three yr were published. Dry matter (DM) harvested dropped from the 4th to 5th yr overall all swards by 1.5-2.0 t ha-1 but response to N was maintained (17.4 and 24.4 kg DM (kgN)-1 in response to 90 kg N ha-1 in 1979 and 1980, respectively) despite reductions in summer yields relative to unfertilized swards. Blanca swards produced significantly less DM harvested than all other cultivars in 1979 and all cultivars in 1980 except for Olwen. Clover DM harvested continued to fall from 1977, the mean for the unfertilized treatment in 1980 being 55% of that in 1979. Up to 1980 Sabeda swards produced more clover DM harvested than Blanca swards. Linear regressions between annual clover content at zero N and at each spring N level for each sward type over 5 harvest years were very highly significant. All cultivars used responded similarly to spring N. Further work to develop a method for predicting the effect of spring N on clover content of given swards is required.