The effects of simulated summer‐to‐winter grazing management on herbage production in a grass–clover sward

Abstract

The effects of summer‐to‐winter simulated grazing management factors, namely defoliation interval (INT: 21, 42, 56 or 84 d), defoliation height (DH: 2·7, 3·6, 5·3 or 6·0 cm) and final defoliation date (FIN: 23 September, 4 November or 16 December) on herbage production in a grass–clover sward were studied. Treatments were imposed between July and December 2008, with all plots under common management in the following March to June 2009. The 42‐d INT achieved the highest (P < 0·001) total herbage yield at 11·00 t DM ha−1. Shorter (21 d) and longer (56–84 d) intervals reduced annual clover herbage yield and biological nitrogen fixation estimates. Lowering DH from 6·0 to 2·7 cm in the summer‐to‐winter period increased sward clover content and clover herbage yield through to the following June, 6 months after treatments ended. Delaying FIN from 23 September to 16 December had no significant effect on annual clover, grass or total herbage yield. Spring–summer clover herbage yield was positively correlated with spring–summer clover stolon mass (R2 = 0·54, P < 0·001) and, to a lesser extent, light penetration through the sward in the previous winter (R2 = 0·16, P < 0·05). A 42‐d INT with low DH (2·7–3·5 cm) is therefore recommended for grass–clover swards.

The effect of fertilizer nitrogen input to grass-clover swards and calving date on the productivity of pasture-based dairy production

“…It seems that grazing during the winter by the cows on LS0N favored clover stolon survival, perhaps by allowing greater light penetration to the base of the sward during the winter (Phelan et al, 2014). A similar result was found in Northern Ireland by Laidlaw and Stewart (1987) and Laidlaw et al (1992), who found that grazing by sheep over the winter improved clover content of pasture DM in the following spring relative to no grazing between November and March.…”

“…The optimal temperatures for growth of white clover are higher than perennial ryegrass (Lolium perenne) and this makes clover vulnerable to competition by perennial ryegrass particularly during the winter and early spring (Davies, 1992). Previous plot-scale investigations by Laidlaw and Stewart (1987), Laidlaw et al (1992) and Phelan et al (2014) showed that carrying high covers of pasture for long periods over the winter and early spring was detrimental to white clover survival and, hence, the subsequent productivity of swards. Furthermore, the application of fertilizer N to grass-clover swards in spring to increase grass production can be detrimental to the white clover component of the sward (Laidlaw et al, 1992;Chapman et al, The effect of fertilizer nitrogen input to grass-clover swards and calving date on the productivity of pasture-based dairy production 2017).…”

Herbage and nitrogen yields, fixation and transfer by white clover to companion grasses in grazed swards under different rates of nitrogen fertilization

“…Sward management practices, such as frequent grazing (Egan et al ., ; Enriquez‐Hidalgo et al ., ), have been shown to increase sward white clover content. Additionally, frequent (Ledgard and Steele, ) and tight (Menneer et al ., ; Phelan et al ., , ) grazing and/or cutting practices can also increase N fixation. Although the suppression of legume N fixation by N fertilizer is widely accepted (e.g.…”

Comparison of perennial ryegrass,Lolium perenneL., ploidy and white clover,Trifolium repensL., inclusion for herbage production, utilization and nutritive value

“…Recent work has shown that rotational grazing and frequent, tight grazing (Phelan, 2013;Phelan, Casey, & Humphreys, 2014) can maintain a high sward white clover proportion under grazing scenarios with high N fertilizer levels and high stocking rates (Egan et al, 2018;Enriquez-Hidalgo, 2014;Enriquez-Hidalgo et al, 2016).…”