32 IREC Farmers' Newsletter No. 198 — Spring 2017 main aims. The first is to assess the impact of varying surface irrigation management strategies (scheduling and frequency) on nitrogen use efficiency, water use efficiency and overall system profitability. The second is to develop irrigation design criteria that allow precise application of water in basin irrigation layouts, such as bankless channel systems. Commercially relevant trials The Max project established cotton and maize trial sites with IREC at Darlington Point and ICC at Numurkah, respectively, to investigate the interaction between irrigation and nitrogen, as well as other management interactions. In the cotton trial, treatments were irrigated with siphons in order to achieve the most accurate water control at a commercial scale. The intention was to obtain data to guide system targets for optimising scheduling when using automated irrigation layouts. In the maize trial, treatments were irrigated using fully automated border check irrigation systems. At both sites, different irrigation schedules that applied approximately the same amount of water over the season were tested. The aim of both the cotton and maize trials was to see what irrigation and nitrogen strategy produced the best productivity and nitrogen recovery in the two crops, to provide information for greater management flexibility, within the realms of commercial risk taking. Cotton at Darlington Point In the cotton trial, there were three different irrigation schedules: l short deficit — watered every 7 days at -30 to -40 kPa l standard deficit — watered every 14 days at -70 kPa l long deficit — watered every 19 days at -110 kPa. Figure 1 shows the soil tension data from gypsum blocks for each of the irrigation treatments. Soil tension is the measure of how much suction a plant needs to extract water from the soil. A zero reading means the soil is waterlogged. Each irrigation treatment was overlain with two different nitrogen rates, with nitrogen supplied as urea: l  180 kg N/ha — 90 kg N/ha top dressed on 21 November and 90 kg N/ ha on 28 December l  270 kg N/ha — 90 kg N/ha top dressed on 21 November and 180 kg N/ha on 28 December. The treatment plots were 1.38 ha each and replicated three times in a factorial design. Each plot was picked commercially, modules were weighed on a weigh trailer and each module was ginned individually at a commercial gin. Cotton results The trial at Darlington Point was planted at 18 seeds/linear metre into fairly wet conditions with minimal land preparation. Establishment resulted in a plant stand of 11 plants/m. All treatments were irrigated with the same volume of water on 3 January, and thereafter different irrigation timings were imposed until a final irrigation to all treatments on 15 March (Figure 1). The first fertiliser application was late in the third week of November, followed by a second application in the fourth week of December. There was no insecticides used throughout the entire season. Overall yield was 9.8 bales/ha, 9.1 bales/ha and 8.4 bales/ha for the short, standard and long deficit irrigation treatments respectively. Gin turnout was 42% for all treatments. The short deficit treatment matured 26 days later than the long deficit and 19 days later than the standard practice (Table 1). The greater nitrogen application rate increased yield in all treatments but not significantly (Figure 2). Cotton conclusions The short deficit (7-day watering) resulted in a 1 bale/ha or greater yield than longer watering deficit strategies at Darlington Point, on clay loam soils. Evapotranspiration was approximately 0.5 ML/ha greater, harvest date was up to four weeks later and the crop required Data from the cotton trial will be used to guide system targets for optimising irrigation scheduling using automated layouts.