DRIP IRRIGATION DISTRIBUTION UNIFORMITY IN VINEYARDS OF AUSTRALIA: TOOLS FOR MAPPING AND ESTIMATION OF IMPACTS

Abstract

Increasing pressure is being placed on water resources due to the extensive drought and low water allocations in Australia. This has caused a shift to pressurized irrigation systems for many crops. Essential to getting the high returns required is that the irrigation system performs at high levels of distribution uniformity to maximise uniformity of crop and provide more efficient use of water and fertiliser. In commercial situations, field evaluations of drip irrigation systems are often overlooked with many growers taking for granted their system is behaving according to the design specification. Drip irrigation systems theoretically have high distribution uniformities and application efficiencies, however in commercial field systems these theoretical efficiencies can be difficult to achieve. This paper outlines recent research monitoring actual distribution uniformities in vineyards of SE Australia and the impact on total water applied over a season and also fertiliser application. The paper also outlines how satellite derived NDVI remote sensing measurements can be used for targeting sampling strategies to perform performance assessments on drip systems. The paper also outlines the development of a web based interface (http://www.irrigateway.net/tools/du/) developed to simplify the analysis of field collected data and relate this performance to indicators which can clearly be understood by irrigators - such as effects of poor distribution uniformities on seasonally applied water and nitrogen fertigation.This paper addresses these issues and describes implications of poor distribution uniformity on crop performance, especially when watering below maximum crop water requirement and as such falling into a higher risk region on the irrigation:yield production function. This is done using an adapted crop growth model that accepts spatial input data for irrigation and fertiliser.