A silopasture trial helps reduce emissions

There are plenty of benefits of having trees on a farm - they help with carbon storage, increase biodiversity, provide shade and shelter, and help prevent erosion.

On the Fonterra and Nestlé Net Zero Pilot Dairy farm in Whareroa, Taranaki, a silvopasture trial is looking at the benefits of trees planted in paddocks grazed by dairy cows.

The pilot, run with Dairy Trust Taranaki, aims to create New Zealand’s first commercially viable net zero dairy farm within 10 years. Establishing a silvopasture paddock will contribute to emissions reductions through increased carbon sequestration.

Silvopasture is a type of agroforesty that incorporates trees with forage or pasture grazing animals. The trial on the Net Zero Pilot Dairy farm uses native kapuka (griselinia littoralis) and kanuka (kunzea ericoides), chosen for their 10-15m height to minimise competition with pasture.

The species are both salt tolerant, which is important given the farm’s proximity to the West Coast. In July 2024, 220 plants were planted in a 4ha paddock, at different densities, for example 40 stems per ha and 70 stems per ha, to understand the practicality on farm. So, what’s being measured?

Firstly, survival rates. To get any of the benefits, the trees need to survive and grow to maturity. It’s also important to evaluate whether that growth has any negative effect on pasture yield, or the flipside, if there are benefits from the shade provided in the warmer months. The impact of tree spacing on growth will also be measured, and finally, the impact on carbon storage, both in the trees and in the soil.

One challenge has been trying to deter cows from rubbing against the trees in the paddock. A recycled plastic tree guard was installed as a deterrent, but the cows damaged these through rubbing, and the plastic also became brittle in the summer. Scratching posts were tried as an alternative, and while the cows loved them, they didn’t completely deter them from the trees.

Next was a plastic mesh tube that went around the steel fence posts, but the cows rubbed up against these so much they pulled the mesh off the trees.

Finally, a solution was found in Ekidna tree guards, which were installed in May. These guards are designed to imitate the structure of a thorny shrub, allowing livestock to graze safely nearby while offering protection and support for young trees. The cows will continue to be monitored, assessing the effectiveness of the tree guards over time.

Everything trialled on the Net Zero Pilot Dairy farm needs to be scalable or available to all dairy farmers in New Zealand, and solutions need to be good for the farmer, good for the cow and good for the milk.