Effect of deferred grazing during late spring and summer on pasture productivity in Waikato and Bay of Plenty hill country

Abstract

Deferred grazing is a commonly used tool to manage feed surpluses. The effect of deferred grazing on pasture nutritive value and productivity was quantified in a split-paddock trial on three hill country farms in Waikato and Bay of Plenty from October 2018 until May 2020. Livestock were excluded from the deferred pasture between mid-October 2018 and March 2019. Thereafter, both treatments were rotationally grazed in common with cattle or sheep depending on the farm. Total annual dry matter production was 15% greater in the deferred than grazed treatment for the 12 months after deferring (8.9 vs 7.7 t DM/ha, P<0.05). Metabolisable energy (ME) values at the end of the deferred period were lower in the deferred than grazed treatment (P<0.01) but similar in both treatments thereafter. The content of legumes other than white clover (Trifolium repens) was higher in deferred than grazed pastures in spring 2019 on one of the farms (treatment × farm interaction P<0.05). Ground cover of perennial ryegrass was greater and the area of bare ground smaller, in the deferred than grazed treatment on three of five occasions from after the beginning of the deferred period until up to 8 months after deferring (P<0.05). There was no difference between treatments in decomposition and stabilisation of organic matter (P>0.05). The topsoil water content was higher in the deferred than grazed treatment for 12 months after deferring. In comparison to regular grazing between October and March, deferred pastures provided drought feed in autumn 2019. Pasture productivity was increased after the deferred period without negative impacts on ME.