— 27 IREC Farmers' Newsletter No. 200 — Spring 2018 Distribution uniformity With each irrigation event, the goal is to have distribution uniformity as high as possible. In the trials, distribution uniformity was high with half of the events having a distribution uniformity greater than 90% (Figure 6) A high uniformity does not guarantee efficient irrigation. To achieve such uniform applications, often more water is applied than is necessary. Water savings One benefit of optimising flow rates and cut off times for irrigation is the potential for water savings. As the double siphons were generally run for far too long, resulting in excess tail water, the single siphons often saved considerable amounts of water, in this trial. If irrigators increase flow rates, excess tailwaters can result if siphons are not pulled at the correct time. This can significantly reduce the efficiency of an irrigation. On average the single siphons saved 0.24 ML/ha per irrigation compared with double siphons. To put this saving into perspective: 0.24 ML/ha x 6 irrigation events across the season = 1.44 ML/ha. Multiply this by a typical cotton area, e.g. 500 ha, then 720 ML of water could be saved over the season on a 500 ha farm. That’s enough water to grow another 72 ha of cotton. By optimising the irrigation event with double siphons, the water saving between the measured and optimised events was 0.4 ML/ha/irrigation. To put into perspective: 0.4 ML/ha x 6 irrigation events across the season = 2.4 ML/ha. Multiply this by a typical cotton area, e.g. 500 ha, then 1200 ML of water could be saved over the season on a 500 ha farm. That is enough water for another 120 ha cotton. Figure 6. Distribution uniformity of individual irrigation events for single and double siphon treatments 0 10 20 30 40 50 60 70 80 90 100 Irrig. 1 Irrig. 2 Irrig. 1 Irrig. 2 Irrig. 1 Irrig. 2 Irrig. 1 Irrig. 2 Irrig. 1 Irrig. 2 Border Rivers Border Rivers Gwydir (Weemelah) Gwydir (Weemelah) Gwydir (Moree) Gwydir (Moree) Namoi Namoi Sth NSW Sth NSW Distribution Uniformity (%) Distribution Uniformity Single siphon Double siphon Acknowledgements Growers and consultants who provided trial sites and assistance. CottonInfo Regional Extension Officers, Amanda Thomas, Geoff Hunter, Sally Dickinson and Annabel Twine John Smith (former NSW DPI Irrigation Agronomist) for collating the soil sample results Joseph Foley & Malcolm Gillies, NCEA, USQ for conducting the irrigation evaluations CRDC for funding the trials Further information Kieran O’Keeffe M: 0427 207 406 E: [email protected] — 27 IREC Farmers' Newsletter No. 200 — Spring 2018 Save water and nitrogen on cotton BACK TO CONTENTS PAGE