It was a shock on Saturday to see Weatherzone predicting 28ºC for today and tomorrow, and mid 20’s to Tuesday.
Similarly, YR is predicting 25ºC for today, 26ºC Saturday, 27ºC Sunday, 28ºC Monday and 29ºC Tuesday.
Hence the daily evaporation and crop water use is going to jump right up.
You need to water as soon as possible.
As you may remember from our past season yield diagnosis in 2020 and 2021, the optimum maximum temperature for wheat and canola flowering and grain filling is 28ºC.
Temperatures this high so soon in September are a big worry, as the implications are for higher temperatures over 28ºC later which will reduce wheat and canola grain setting numbers.
An Arizona reference I have used, Mon J. et al (2016), found that in a spray irrigation wheat trial that the canopy temperature minus air temperature values decreased linearly with greater irrigation number.
Although subsoil moisture levels are good, topsoil moisture to 30cm is critical as there are many yield producing roots in this zone.
Hence the old G Dot probes were located at 30cm to assess soil moisture and help make decisions on optimum watering decisions preventing crop moisture stress.
Deeper root soil moisture roots are survival roots still capable of producing high dryland yields as we found in 2021 aided by the low maturing temperatures.
The critical moisture sensitive stage for wheat starts at the boot stage coming up very soon and for canola the current flowering pod set stage.
~ John Lacy is an independent agriculture consultant based in Finley.
