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The effects of frequency of defoliation on the yield response of a perennial ryegrass sward to a wide range of nitrogen application rates

Published online by Cambridge University Press:  27 March 2009

D. Reid
D. Reid
Affiliation:
The Hannah Research Institute, Ayr
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Summary

In a 3-year experiment on a sward of S. 23 perennial ryegrass 21 rates of nitrogen fertilizer ranging from 0 to 897 kg/ha were applied annually on plots cut three, five or ten times per year. The cutting dates within each frequency were decided on the basis of herbage growth stage. Four-parameter exponential curves fitted to the herbage yield data show that the pattern of response to nitrogen application in the five cuts per year treatment was markedly similar to that reported for a previous experiment (Reid, 1970). Alterations in the cutting frequency affected the pattern of dry-matter yield response to nitrogen, but not that of crude-protein yield response. The combined effects of cutting frequency and nitrogen rate are illustrated by response surfaces fitted to the dry-matter yield results using an extension of the equation for the curves fitted to the individual frequency results. These surfaces show that as the number of cuts per year was increased the total yield and the response to nitrogen decreased, but the response was maintained to an increasingly high nitrogen rate. The practical implications of the results are discussed in relation to intensive grazing managements for dairy cows.

Type
Research Article
Information
The Journal of Agricultural Science , Volume 90 , Issue 3 , June 1978 , pp. 447 - 457
Copyright
Copyright © Cambridge University Press 1978

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