Farmers eye shelter belt options
Farmers will most likely look to slower growing shelter belts with less wind-catching foliage as replacements for the tall lines that took a hammering on Canterbury farms during the extreme September and October wind storms.
Shelter belts are expected to have less "sail" area and be more open to trimming to withstand the next big blow matching the ferocity of the 2013 and 1975 storms.
Retired forestry researcher Nick Ledgard said much thought was going into replacing felled shelterbelts with more durable replacements.
He said better management of shelter belts was needed to prevent damage to fences, buildings and the ground surface from uprooted farm trees and dairy farmers wanted alternatives to protect centre pivot irrigators.
"I think we have to manage the likes of our shelter belts more and choose species with smaller crowns and less wind-catching sail areas. We can always manage radiata but there might be other alternatives."
He said corsican pines might be a good option as they were slower growing with lighter branches and did not spread in the Canterbury Plains as they did in other areas to create wilding problems.
Leyland cyprus clones also withstood trimming and native species could have a larger role to play on the Plains. Native trees were hard to find as equivalents for fast growing tall species such as radiata on the Plains, but there were many hardier native shrub species that could be used for shelter and allow centre pivot irrigators to pass over them.
Mountain flaxes might be used instead of flax to control their fence spread as might pittosporum species and shrubs with densely tangled foliage provide shelter for livestock. Ledgard said there was still be a role for radiata pine.
"Definitely (we will need radiata pine), but we need better management for its porosity ... so it lets more wind through, but slows the wind down. It doesn't make a complete barrier and its height can still be managed."
Ledgard is co-ordinating a series of 10 workshops in the South Island to expose farmers to the best ways of using trees in farmland from April 22 to May 15.
Former NZFFA president Pat Milne will talk about how to make shelter belts more stable with slower growing species and reducing their height at the Trees on Farms' workshops, run by the New Zealand Farm Forestry Association (NZFFA) and backed by the Sustainable Farming Fund. Irrigation NZ chief executive Andrew Curtis will look at trees to protect centre pivot irrigators from wind. About 800 irrigators were damaged during last year's storm.
Other speakers will investigate the roles of trees in intensively managed irrigated farms and in the hill and high country to control nutrient leakage, provide farm investment as tree lots, develop ground-durable timber for farm posts and assist 'green tick' farming so farmers can sell farm products to market places needing to be reassured about the welfare of animals.
Ledgard said consumers wanted to know livestock were raised in an animal-friendly environment with trees for shelter and shade.
He said dairy farmers had come to them to look at shelter options for calf-rearing areas and cow herds and more studies were needed to understand how much water loss was prevented from tree lines after irrigating.
Riparian plantings were helping farmers intercept silt and nutrients before they reached waterways and trees could be greater used for critical source areas of extensive nutrient leakage such as gullies downstream from feedpads or stock truck areas, he said.
Ledgard said it would be virtually impossible for farmers to win the supreme title in the Ballance Farm Environment Awards today unless they had a strong commitment towards trees. "You only have to see past winners to see that."
Farm forestry leaders hope to convert the next generation of farm managers to tree growing for its many benefits.