Maximising the subterranean clover content on a summer-dry Wairarapa hill-country farm through grazing management

Abstract

Tokaroa Farm is a 608-ha sheep and beef farm, in the Wairarapa. Paddock slopes range from flat to steep (>25°) with a predominance of gentler north facing slopes and steeper south facing slopes. Annual rainfall is 810 mm and average summer dry is three months. Resident subterranean (sub) clover (Trifolium subterraneum L.) populations were identified on an uncultivatable north-west facing hill slope in 2015, and a management plan devised to increase its contribution to pastures.
Exclosure plots showed that an eight-week spell in spring 2016 increased resident sub clover groundcover from 13 to 54%, while in the lightly grazed paddock control sub clover increased from 10 to 28%. There was a positive linear relationship (R²=0.51) between the total number of established sub clover seedlings on 30 March 2017 and the previous spring sub clover groundcover (%) on 25 November 2016. In October 2017, the effect of the spring 2016 exclosure treatments was still evident with 57% sub clover groundcover in the eight-week spelled areas compared with 37% in the control despite all the exclosures being grazed in 2017.
Sub clover management strategies were developed, using slope and aspect, and applied to a GIS map of Tokaroa Farm. This suggested that 53% of the farm could have sub clover overdrilled into it and 29% could have the resident sub clover population actively managed and/or oversown with sub clover seed.