OPEN HYDROPONICS OF CITRUS COMPARED TO CONVENTIONAL DRIP IRRIGATION BEST PRACTICE: FIRST THREE YEARS OF TRIALLING AND AUSTRALIAN EXPERIENCE

Hydroponics is a system of growing plants in an inert media (e.g. rockwool), supplying the plants’ nutrition using mineral salts dissolved in the irrigation water and irrigating frequently throughout the day. “Open Hydroponics” (OH) is a system where trees are grown in soil, but nutrient needs are managed similarly to hydroponics and trees are irrigated throughout the day. OH is a relatively recent production innovation, and is being adopted around the world, and there are anecdotal reports of superior yields attributed to OH. However, OH programs do not necessarily consider the soil as a critical part of the production program. This has raised concerns regarding soil acidification, waterlogging and nitrate leaching. Little objective scientific data are available on OH, and there is an industry-wide knowledge gap. A replicated extension trial is being conducted to compare citrus OH to conventional practice in young citrus. The first three years of data indicates no differences in yield, soil and/or leaf nutrient dry matter content to conventional best practice. Soil solution data is highly variable but indicates that adequate levels of nitrogen are present in the soil for both programs. Data suggests acidifying irrigation water has no benefit and water use in pulse irrigation is higher than best practice conventional.