With Damian Jones
Most areas across the Murray Valley had an exceptional start to the season with a much wetter than average April. Deniliquin had 93mm, Kerang 89mm, Moulamein 73mm, Shepparton 132mm and Tocumwal 88mm. This set up many paddocks for cropping in 2020 without the need for pre-irrigation, and allowed timely, if not a little early, sowing for most crops. Warm soils and good soil moisture have seen crops to get off a good start. It has also been a good start for graziers with the common complaint of having too few livestock. There are many volunteer cereal crops that are now in head which are providing feed but are potentially a source of crop fungal disease inoculum for later in the season.
As the season has progressed, an east/west divide has emerged. Those in the west of the region have seen the promise of good winter rains evaporate with below average May and June. Areas east of an imaginary line running roughly north/south through Deniliquin and Echuca have seen winter rainfall being close to average. A common theme on the variability of rainfall across the districts “we got a couple of mil but next door got 30”.
This starts to make irrigators think about the first irrigation. Timely application is needed to ensure the crop doesn’t stress and lose yield potential. This can occur quite quickly where rainfall rather than pre-irrigation has got the crops away, as there is no or minimal deep soil moisture reserve in the west.
As a general observation, timely sowing and good moisture have produced crops with high biomass, which can quickly become water hungry monsters.
Nitrogen management is critical to managing crop biomass – local irrigators have been setting their yield targets somewhat conservatively with the anticipation of only 1 spring irrigation and have reduced the amount of N accordingly. A couple have paddocks with higher soil N and these will be the crops that will be pushed to higher yields if the water is available and at a viable price. But as the ICC saw last in last year’s Smarter Irrigation for Profit 2 trials, irrigation can’t bring back lost yield, it needs a crop that can respond with sufficient tiller numbers or biomass to drive target yields.
To Irrigate or not?
Check out our ‘Irrigate or not’ gross margin spread sheet and info graphics about when to water to optimise yield.
NSW DPI also have some great information about best practice irrigation management.
GRDC have a fact sheet based on crop surveys conducted by the ICC at https://grdc.com.au/the-costbenefit-of-irrigating-wheat-under-drought-conditions that details the steps needed to determine if irrigating wheat is profitable, based on tiller/shoot counts.