Dr Ron Hutton says using neutron probe measurement to determine soil water content can help reduce nutrient losses.

Viticulture researchers are investigating how to manage irrigation in vineyards to avoid nutrient losses through surface run-off and deep drainage, while maintaining optimum nutrient requirements for vines.

Nutrient concentrations of fruit from six Chardonnay vineyards were measured over three seasons.

'Providing canes are left in the vineyard after pruning, the main loss of nutrients should occur when fruit is removed from the vineyard at harvest,' said Dr Ron Hutton, deputy director of the National Wine and Grape Industry Centre (NWGIC).

'The amount of nutrient removed by the crops was determined by the yield level and the concentration of particular nutrients.'

Dr Hutton said crop nutrients give an indication of how much fertiliser needs to be applied to replace the nutrient loss.

The work is part of a Co-operative Research Centre for Viticulture project in the Riverina. The NWGIC, in partnership with the CSIRO and the Victorian Department of Primary Industries, have undertaken a collaborative project to quantify the extent of nutrient losses in irrigated vineyards and how they relate to irrigation practices, fertilizer inputs and whole vine nutrient requirements.

'Some consideration is also needed for nutrients lost through surface run-off and following rainfall or irrigation that leads to water drainage below the rootzone,' Dr Hutton said.

'This is particularly relevant for nitrogen, which is highly mobile and easily transported through the soil with any water movement.

'Ideally, losses from run-off and drainage should be kept to a minimum, but some losses are inevitable where a leaching fraction is required to avoid salt build-up in the root-zone, or rainfall occurs on already full soil profiles.'

Dr Hutton said that because determining the extent of total nutrient losses was not practical in a commercial vineyard situation, researchers were now working on how to match nutrients to vine requirements.

'Vine growth may already be reduced before nutrient deficiencies can be seen and applying more nutrients than required can result in unwanted vigour,' he said

'Managing irrigation to avoid excessive drainage below the rootzone is part of the answer, as is the timing of fertilizer applications to help keep additional nutrient requirements to a minimum.

'Our goal is to produce quantifiable information that growers can use to improve their irrigation and fertilizer management, to ensure balanced vine growth and avoid some of the problems that nutrient deficiency or excess can have for fermentation and wine quality.'

Contact: Dr Ron Hutton, WaggaWagga, (02) 6933 2108.

This story appears in Agriculture Today.