Increasing irrigation water and controlling vigour by collecting runoff from the mid row of vineyards

Apart from increasing the scope for water harvesting there was interest in whether vineyard treatments could be used to manage vegetative growth early in the season and reduce recharging of the saline groundwater which is at a very high level in the region..

The replicated trial compared a normal cover crop treatment, surface sprays of infiltration-reducing chemicals and black plastic. It was set up in a block of nine year old Shiraz vines at Powder bark Ridge Vineyard on sandy loam with a high gravel content and clay at depth, a common soil type in the region. Measurements spanned vine growth and fruit quality parameters as well as soil moisture and the amount of water harvested and drained off to a dam. Trials were conducted over two years, both of which had lower than average rainfall.

Although black plastic meant a high initial cost this has to be weighed against its superior efficiency, enabling 90% of rainfall to be collected while there was almost total infiltration on grassed surfaces. Bare surfaces sprayed with sealant enabled run-off of 28% of rainfall. It was noted, however, that while sealants did not work well on loams with some surface organic matter they would continue to be a useful option for roaded catchments. Another observation was that ultra violet light resistance properties might increase the life of plastic.

The most important outcome is that it has been demonstrated that the plastic sheeting technique is viable. In the process grape growers in the region have been provided with additional information about the vineyard environment.