2007 Annual Report - Central Queensland University

2007 Centre for Plant & Water Science Annual ReportOXYGATION: POTENTIAL FOR IMPROVED YIELD, WATER-USEEFFICIENCIES AND ENVIRONMENTAL MANAGEMENTSUMMARYLarge scale trials, planted with cotton, chick-pea and sorghum have been conducted inEmerald to verify earlier promising results from aeration of irrigation water in glass-house andscreen-house trials. With replicated plots each of 0.4 ha, and with drip-line lengths of 270 m,these trials have allowed a critical examination of the benefits of oxygation – the aeration ofirrigation water – with venturi valves. Results from the 2005 and 2006 and 2008 cotton trialswere encouraging. In 2005 aerated cotton provided a 29% increase in yield with an associated27% improvement in crop water-use efficiency i.e. increased yield using less water. Yields andwater use efficiencies of the subsequent 2006 and 2008 cotton crops also respondedsignificantly to the aeration treatment (16% and 12% higher yields respectively and improvedin crop water-use efficiencies of a similar magnitude). No cotton was planted in 2006-07 due toinsufficient irrigation water availability.The process of soil aeration is one of the most critical determinants of plant productivity. Asirrigation water enters the soil, whether overhead, flood or drip it purges the soil pores of airand can often result in anoxic conditions to the detriment of plant growth and water useefficiencies. In a range of glass-house/shade-house experiments oxygenation, i.e. hyper-aeratingirrigation water supplied through subsurface drip irrigation systems, has consistently producedenhanced growth, yield, and water use efficiencies (WUE).Although the use of SDI leads to demonstrable increases in WUE over other irrigation methods,its potential (in yield advantage and adoption) is still not being reached. If aerated SDI wouldprovide additional increased yield, and were to reducing irrigation rates, it would have greaterappeal to growers. Increased attractiveness and consequently take-up rates of SDI techniqueswould then have a positive impact on the utilization of Australia’s water resources.The project aims to achieve three main objectives:1. Elaborate on the specific mechanisms by which plant growth, yield and water useefficiencies are affected by increased root-zone aeration, to include a study of the plantgrowth regulators abscissic acid and cytokinin, and of nutrient availability and uptake.2. Develop a commercial-scale methodology (i.e. identify and resolve any practicalconsiderations for the use of aerated SDI).3. Conduct a cost benefit analysis and modelling.Agreement was reached with an established cotton grower in the Emerald area (gypsic vertisol)to establish a system capable of running suitably designed trials that conform to acceptedstatistical analysis. A large scale trial (with treatment plots of 0.4 ha) was superimposed uponcommercial production at a site initially set up by the Qld DNRM, and co-managed with CQU.Analysis of data from the 2005 and 2006 cotton experiments have been completed howeverdata from the chickpea and sorghum trials of 2006/7 are yet to be undertaken.The data collected from these experiments employing the venturi principle (Mazzei aerators)trialling various rates and under varying soil moisture contents have included both soil andplant based parameters to assist in interpreting the measured biomass and yield effects.30