Long term sustainability of drip irrigation in vineyards

Abstract

Drip irrigation, is used extensively in Australian vineyards to conserve water. As this project began in 2006 there were believed to be soil problems that threatened the long-term sustainability of drip irrigation.

Summary

rrigated vineyards in Australia have seen extensive adoption of drip irrigation. At the start of this project there was concern about the sustainability of drip irrigation based on previous field observations. Drip irrigation conserves water but the concentrated nature of its application was believed to cause serious soil structural decline directly under drippers. This project aimed to identify such decline under drippers in Barossa Valley vineyards, to establish the causes of the decline and to suggest management and monitoring strategies to deal with the problem.

To identify such decline we adopted a “paired site” approach and examined subsoil structural problems, at depths of 30-50 cm, directly under drippers, midway between well-spaced drippers (>2 m) and at nearby non-irrigated control points. While we were encouraged to find no evidence of any preferential subsoil structural decline under drippers, we were surprised to find that all the subsoils we examined were of such generally poor structure that there was little prospect of further decline. However, we also realized that application rates in the Barossa Valley are dwarfed by those used elsewhere and proceeded to extend our investigation to the finer-textured soils of Sunraysia and the Murrumbidgee Irrigation Area (M.I.A.). The story here was no different and it became clear that the structural status of subsoils in vineyards is generally poor and is probably undermining good water use efficiency by vines. In 22 distinct soils air-filled porosities were universally very low, resistance to root penetration was high and infiltration rates were frequently poor. A comparison of root length density with subsoil structural properties strongly suggests that poor aeration poses the chief limitation on root proliferation and water use efficiency.