Winepress - August 2024

Long spur pruning

Vineyard trials point to cost and labour savings

Penny Wardle

A permanent cordon is basically a trunk on its side.

AN ALTERNATIVE pruning method could cut costs of growing Sauvignon Blanc without compromising wine quality, early trial results suggest. At Grape Days 2024 in Blenheim, a poster presentation by Nelson Marlborough Institute of Technology student, Tracy Gilmore, set the scene. Vineyard labour costs were up 236% since 2013 and cane pruning was the most expensive activity, contributing 22% of operating costs.

Yuichi Ando, field trial coordinator for Bragato Research Institute, told Grape Days delegates that “labour shortage concerns became a serious crisis, under 2020 Covid restrictions”. Long spur pruning could ease these worries, “reducing labour while maintaining yield and quality”.

The viticulture research technician shared results of the fourth and final year of a long spur pruning trial. The Marlborough norm of cane pruning Sauvignon to four canes is compared with long spur pruning to four and five buds.

Yuichi said long spur pruning could save 80c to $1.40 per vine, depending on whether it was done mechanically or by hand. However, these savings may not be expected in the year one conversion as it may require extra cost to set up properly. The latest cost-benefit analysis – based on tonnes harvested in three trial sites, gross profit, and pruning savings – put long spur pruning mostly ahead on two vineyards. But on the third, profitability lagged at both four and five buds.

“To be successful with long spur pruning, initial setup is a key,” Yuichi advised, and the conversion may take over two years. In year one, canes on the bottom wire must be strongly attached to the trunk, and loosely wrapped to allow sap flow. Even spur spacing maximises light to the basal buds which improves fruiting the next season. And filling the gap between the cane ends maximises the space for spur selection and fruiting. Growers say these steps will increase the longevity of cordon life and reduce maintenance costs in future. Juice, acidity, sweetness and aroma were not significantly different in wines made from cane versus long spur pruned vines, Yuichi said.

Asked whether long spur pruning protected against Grape Vine Disease (GVD), he quoted the advice of Dion Mundy, Plant & Food Research Senior Scientist, that the method reduced the risk of primary infection compared with cane pruning. Symptoms generally showed up earlier, giving time to remove affected cordons before pathogens reached the trunk. And fewer cuts around the vine head protected against infection.

In Marlborough vineyards, long spur pruning is also filling gaps where GVD has killed vines and as a method to tackle overvigorous vines. Ian Buunk of Woodbourne Farm, Fairhall, long-spur prunes to two to five buds, to stretch across gaps where vines died of GVD. “It’s delaying the inevitable plus we can barrel-prune to reduce labour so it’s cheaper,” Ian says. The vineyard was planted in the early 1990s so vines were 2.5 metres apart, compared with today’s 1.8 metre standard.

Matt Gallop, Constellation vineyard manager, said long spur pruning was employed at a “hugely vigorous” site at Tua Marina where buds were so far apart it was a struggle to get lateral length short enough. “We have no labour shortage, this is simply to control vines so vigorous that fruit drops due to lack of light.” This winter would be the third of a regime of year-on year-off spur and cane pruning, Matt said.

More information on the long spur pruning research: bri.co.nz/long-spur-pruning.