Mark Krasnow (left) with Stewart Field in the EIT vineyard.

EIT and Thoughtful Viticulture Ltd are conducting Hawke’s Bay trials for a New Zealand Winegrowers-funded research project aimed at using water more efficiently to irrigate grapevines.

Established by Dr Mark Krasnow three years ago, Thoughtful Viticulture is collaborating with the School of Viticulture and Wine Science in undertaking the trials at sites in the Bridge Pa Triangle.

Heading the project for EIT, viticulture lecturer Dr Stewart Field says the irrigation trials will continue throughout the growing season. The exercise is aimed at helping the industry optimise its use of a limited resource.

“That’s becoming an increasingly important consideration as territorial and local authorities look to better regulate the use of water in agricultural endeavours.”

The project, which focuses on Chardonnay and Merlot grown on six separate sites in the Bridge Pa Triangle by a number of different growers, will also demonstrate EIT’s research capabilities.

The trials centre on the use of a pressure chamber – more colloquially known as a pressure ‘bomb’ – to measure water stress in vines. The usual method for
determining when to irrigate vines is to measure soil moisture levels.

The research trials will compare results from the conventional and pressure chamber methods.

Using the pressure chamber method, the petiole is fed through a gasket, which seals the leaf blade into the chamber. The chamber is then pressurised, and as the pressure increases at some point sap will be forced out and will be visible at the cut end of the petiole. The pressure that is required to do so is equal and opposite to the water potential of the leaf.

“If the vine is well watered it takes hardly any pressure to record the result,” says Stewart.