IRRIGATION BEST MANAGEMENT PRACTICES - THE AUSTRALIAN EXPERIENCE

Processing tomatoes are grown under irrigation in the semi-arid environment of south eastern Australia. Water supplies are limited, and there are social as well as environmental pressures on growers to maximise their water use efficiency. Studies were conducted over three years (1997-2000) to identify, document and promote best management practices for the irrigation of processing tomatoes in this region. A grower census was conducted in early 1998 to gather information on water use, irrigation practices and problems. Both drip (53%) and furrow (47%) irrigation are used extensively. Water use efficiency (WUE) measured as tonnes of fruit per megalitre (Ml) of water applied, varied from 10t Ml^-1 in the top 15% of growers using drip or furrow to 4 t Ml^-1 for the bottom 15% of furrow irrigators. Most of the top growers (top 15% WUE) used some form of soil moisture monitoring, but very few growers measured the amount of water applied. On-farm demonstrations, using various devices for measuring soil moisture levels, served to illustrate irrigation problems and promote the value of monitoring to growers. Nine commercial tomato crops were instrumented in total -3 under drip and 6 under furrow irrigation. Typical problems included the loss of irrigation water through deep percolation under both irrigation systems, establishment of perched water tables, and plant disease arising from over-watering. Good irrigation management and design were found to be crucial to achieving high WUE, irrespective of the delivery system.