Keep an eye on daily ETo figures via the link to the SENRMB weather station network at left (nrmWEATHER). Suggestions on how to use this information can be found on the PIRSA website, but regular updates will be provided on this site. You can also look at the soil water graphs posted regularly on this site.
It is important at this time of the year to inspect all aspects of your irrigation system and ensure that it is operating according to design - do not allow maintenance problems to cause you to fall behind in your irrigation schedule.
To start with, make use of a fundamental system component - your water meter. A water meter provides simple information, but it is information that can be used to assess a variety of things. So it is important that you are familiar with your meter and know how to read it properly.
For example, to calculate the depth of irrigation applied (mm) you can use the following formula:
Depth Applied (mm) = Total Volume Applied (KL)
Area (ha) x 10
To find the Total Volume Applied simply subtract the start meter reading from the end meter reading - the time taken doesn't matter, just as long as you know the area irrigated between readings.
This calculation does not account for under or over-irrigation caused by poor system uniformity, but is useful for considering the level of water input against crop water use (i.e. daily ETc is given in mm). Particularly for centre pivot applications, this calculation will indicate whether the actual depth of irrigation applied is consistent with the designed application depth for the rotation speed used.
Keep a record of meter readings through the season and come back to this site for more ways in which to use this information.
Michael Zerk
Rural Solutions SA
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