期刊
GRASS AND FORAGE SCIENCE
卷 72, 期 3, 页码 556-567出版社
WILEY
DOI: 10.1111/gfs.12258
关键词
nitrogen application rate; leaf stage; protein fraction
类别
资金
- Dairy Consortium, Chile
The objective of this study was to evaluate the effects of defoliation frequency (either at two-or three-leaf stage) and nitrogen (N) application rate (0, 75, 150, 300, 450 kg N ha(-1) year(-1)) on herbage carbohydrate and crude protein (CP) fractions, and the water-soluble carbohydrate-to-protein ratio (WSC: CP) in perennial ryegrass swards. Crude protein fractions were analysed according to the Cornell carbohydrate and protein system. Carbohydrate fractions were analysed by ultra-high-performance liquid chromatography. Sward defoliation at two-leaf stage increased the total CP, reduced the buffer-soluble CP fractions and decreased carbohydrate fractions of herbage (P < 0.001). The effect of defoliation frequency was less marked during early spring and autumn (P < 0.001) than for the rest of the seasons. An increase in N application rate was negatively associated with WSC, fructans and neutral detergent fibre (P < 0.001), and positively associated with CP and nitrate (N-NO3) contents of herbage. Nitrogen application rate did not affect CP fractions of herbage (P > 0.05). The fluctuations in CP and WSC contents of herbage resulted in lower WSC: CP ratios during early spring and autumn (0.45: 1 and 0.75: 1 respectively) than in late spring (1.11: 1). The herbage WSC: CP ratio was greater (P < 0.001) at the three-leaf than the two-leaf defoliation stage and declined as the N application increased in all seasons (P < 0.001). The results of this study indicate that CP and carbohydrate fractions of herbage can be manipulated by sward defoliation frequency and N application rate. The magnitude of these effects, however, may vary with the season.
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