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

Authors

  • P. Phelan,

    Corresponding author
    1. Animal & Grassland Research and Innovation Centre, Teagasc, Moorepark, Co. Cork, Ireland
    2. Department of Chemical and Life Sciences, Waterford Institute of Technology, Waterford, Ireland
    3. Animal & Grassland Research and Innovation Centre, Teagasc, Grange, Dunsany, Co. Meath, Ireland
    • Correspondence to: P. Phelan, Animal & Grassland Research and Innovation Centre, Teagasc, Grange, Dunsany, Co. Meath, Ireland.

      E-mail: paul.phelan@teagasc.ie

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  • I. A. Casey,

    1. Department of Chemical and Life Sciences, Waterford Institute of Technology, Waterford, Ireland
    2. Animal & Grassland Research and Innovation Centre, Teagasc, Grange, Dunsany, Co. Meath, Ireland
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  • J. Humphreys

    1. Animal & Grassland Research and Innovation Centre, Teagasc, Moorepark, Co. Cork, Ireland
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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.

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