Effect of Defoliation Severity on Regrowth and Nutritive Value of Perennial Ryegrass Dominant Swards

The height or mass to which swards are defoliated can potentially affect regrowth. A field study was undertaken to determine the response of perennial ryegrass (Lolium perenne L.) dominant swards to defoliation severity over repeated defoliations during a period of low water-soluble carbohydrate (WS...

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Bibliographic Details
Published in:Agronomy journal 2008, Vol.100 (2), p.308-314
Main Authors: Lee, J.M, Donaghy, D.J, Roche, J.R
Format: Article
Language:English
Subjects:
Agronomy. Soil science and plant productions
Biological and medical sciences
carbohydrate content
carbohydrate metabolism
cell respiration
cutting
Defoliation
field experimentation
forage grasses
Fundamental and applied biological sciences. Psychology
height
leaves
Lolium perenne
Nutritive value
pasture plants
pastures
plant growth
regression analysis
Regrowth
sward
tillers
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Summary:The height or mass to which swards are defoliated can potentially affect regrowth. A field study was undertaken to determine the response of perennial ryegrass (Lolium perenne L.) dominant swards to defoliation severity over repeated defoliations during a period of low water-soluble carbohydrate (WSC) accumulation (late spring to mid-autumn due to active leaf growth and relatively high respiration). Five defoliation severities (defoliation to a residual stubble height [RSH] of 20, 40, 60, 80, or 100 mm) were replicated five times in a Latin square design. During a 6-mo period, treatment plots were defoliated seven times using a rotary lawnmower. Analysis of data indicated a quadratic relationship between RSH and total herbage production, with total yields of 12,190, 13,440, 13,730, 13,320, and 11,300 kg DM ha-1 for swards defoliated to 20, 40, 60, 80, and 100 mm, respectively. Regression analyses identified 56 mm as the optimal RSH for herbage production, but there was little biological significance between 40 and 80 mm RSH. Total WSC content per tiller was reduced with increasing defoliation severity. The relationship between WSC content per tiller and subsequent herbage yield was quadratic, with peak herbage yield at 9.4 mg tiller-1 (60 mm RSH). The data indicate that between September (spring) and April (autumn), herbage production of temperate perennial ryegrass-dominant swards is maximized when defoliation severity results in post-grazing stubble heights of 40 to 80 mm.
ISSN:0002-1962
1435-0645
1435-0645
DOI:10.2134/agrojnl2007.0099