7. Set the last irrigation value and then select the two deficits option with an initial deficit of 70mm, a change date of January 1, and the post change deficit of 90mm.
8. Assume no rainfall from the Run Date onwards and use rainfall records to date from the 'Farm' (which is your own onfarm records).
9. Enter a water allocation.
10. Save all changes and then develop two new scenarios which use 90mm and 110mm as the initial irrigation deficit.
11. Open the report generation screen by selecting the 'Report Manager' icon on the toolbar.
12. Compare the initial results using the Multiple Scenario Comparison report and selecting the appropriate farm, field and crop. The optimum scenario for the first irrigation can now be examined in detail using the Scenario Summary reports.
Interpreting the results – What does the report mean?
HydroLOGIC was set up for a field at Narrabri to evaluate the optimum first irrigation date. This field was planted on October 3 with Sicot 71BR and watered up the following day. A range of scenarios were developed using initial deficits of 60, 70 and 90mm, with a subsequent change on January 1 to a higher deficit. The HydroLOGIC report is shown below with results ordered by yield.
The report indicates that three scenarios have the potential to achieve an average of 10.1 bales/ha. At first glance the optimum first irrigation deficit appears to be 70mm and change to 90mm on January 1.
Cotton Seed Distributors Ltd reports the summary report for this scenario schedules the first irrigation date on December 16, with an average yield of 10.1 bales/ha and ranging from 9.6 to 10.7 bales/ha.
Looking at the range of values in the percentile column helps to understand the range of yields predicted and provide an understanding of the 'downsides' (30%) and 'upsides' (70%) attached with a scenario. This reveals that starting with a lower deficit of 60mm and changing to 100mm on January 1 actually has a higher 'upside' of 11.1 bales/ha. The first irrigation date in this case is December 11.
Cotton Seed Distributors Ltd
marketing@alchempro.com
