Tuesday, March 5, 2024

Project looks at Agroforestry benefits in Canterbury plains

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New research is looking at the benefits of planting trees in paddock corners outside the reach of irrigation pivots on dairy systems.
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By Delwyn Dickey for Our Land and Water

Native forest once covered the vast Canterbury Plains, but trees haven’t been a big part of the landscape for centuries. The region has instead become an agricultural powerhouse of pastoral farming, cropping and seed production.  

Agroforestry was always small-scale on the plains and largely revolved around growing radiata pine for timber. Much of this was felled when dairy conversions started ramping up 25 years ago.  

However, trees may make something of a comeback as the region faces increasing climate-related challenges in the future.   

New research is looking at the benefits of planting trees for stock to run under as part of dairy farming systems on some of the estimated 30,000 hectares of dry land in paddock corners outside the reach of irrigation pivots. 

“Agroforestry is an integration of trees and grass. People initially think it’s just forestry, they don’t consider the rest of the farming enterprise and how its included in the same area,” said Kyle Wills, a farming systems consultant with WSP.

With funding through Our Land and Water’s Rural Professional Fund, Wills leads a project looking at the economic benefits of growing forage trees on dairy farms while also gaining carbon credits through the Emissions Trading Scheme. 

By providing shade for cows, the trees could also help reduce milk production loss due to heat stress. The plains could be seeing temperatures above 25degC for three months of the year by the end of this century. 

Wills is among a number of agricultural consultants who anticipate legislation change, making shade for livestock a legal requirement as animal welfare concerns increase.

Two neighbouring dairy farms in the Waimakariri are being modelled on desktop to see how their decisions affect agroforestry design and economic performance. 

Both would have forage poplars and mulberry, with honey locust to fix nitrogen in the dryland corners. One would have a handful of high-value black walnut in the mix, while the other would include natives like kowhai and ribbonwood to attract native birds, with the intention that natives would replace exotics over time, eventually becoming a native agroforestry setting. 

With the project set to wrap up shortly, so far the economics look positive, Wills said.

“There’s lots of opportunity but often for farmers anything that’s not radiata pine for timber is a bit of an unknown. Some individuals might not see any value in indigenous biodiversity, but if they gained biodiversity credits, as they potentially could in the future, they would likely see it differently.”  

Inoculating trees for mushrooms or high-value truffles is another possibility, though not covered in this project. “You certainly don’t see people cutting down trees in a 

truffière for timber,” Wills said. 

More trees on the plains may also make other agriculture more resilient. 

Along with increasing temperatures, strong mid-spring to mid-summer winds are set to get stronger and more common in the future, pulling moisture out of soil and pasture through evapotranspiration, while irrigation is likely to reduce. 

More trees in the environment for shade and to slow down these winds would be of benefit to more than just weary mobile home users out on the roads. 

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