Spectrum of yield outcomes still possible in 2018

After a very dry start to the year, rain over the last few weeks have helped get crops up and away in many dry-sown paddocks. But with many areas that have experienced only minor rainfall events,  there’s understandable uncertainty around what kind of potential can still be achieved. Fortunately, Yield Prophet^® modelling suggests that good yields are still possible, and this can depend more on the paddock history for each paddock than on rainfall so far.

Recent BoM climate outlooks suggest a low probability of exceeding median rainfall over the next few months. However, it’s important to keep in mind that similar forecasts, for this time of year for the Wimmera and Mallee have historically been accurate less than 50% of the time (Figure 1). Whilst there is rain on the horizon, a range of seasonal outcomes are still possible.

Similarly, Yield Prophet^®’s modelling suggests a spectrum of yield results are still possible depending on what happens next. Yield Prophet^® works out the yield potential for a paddock by using the last 55 years of climate records and measurements or assessments of current crop and soil conditions. What is the range of likely yields based on all of these possible outcomes for the rest of the season?

It is pleasing that Yield Prophet^® is still providing a wide range of possible yields for 2018 crops. After a dry start, the big factors defining the remaining potential is paddock history, soil type, and their combined effect on starting soil conditions.

Table 1. Narraport and Longerenong paddock information.

BCG’s Main Site paddock at Narraport, north east of Birchip, is an example of a paddock that still has good prospects (Table 1). This paddock has a high starting N, and a fallow in 2017 combined with good summer weed control translated into a healthy amount of subsoil moisture to support plant growth. Consequently, despite tracking close to decile 1 GSR so far, Yield Prophet^® is predicting a yield between 3.4 – 4.5 t/ha in an average finish (i.e. 30th – 70th percentile), which is in line with previous paddock performance.

For comparison, a BCG trial site on a barley stubble at Longerenong with similar soil texture has had almost twice as much GSR but started off with less in the tank – both in terms of moisture and nitrogen. Although Yield Prophet^® is also estimating a wide range of potential yields depending on how the rest of the season turns out, a much wetter finish and more substantial nitrogen applications will be required to achieve similar yields to Narraport because of the initial soil conditions. Yield Prophet^® predicts a yield between 0.7 – 1.7 t/ha in an average finish.

Neither of these scenarios are surprising, but reinforce the importance of understanding a paddock’s individual soil condition – particularly when the season is off to an uncertain start. Experience, paddock history, and soil sampling can all inform this. Yield Prophet^® provides another helpful tool to validate your thinking about the season ahead, but needs to be set up with the right soil type to be accurate. New features in Yield Prophet^® for 2018 make it easier to get started and keep an eye on all your paddocks – even if you don’t have recent soil test results. For more information on Yield Prophet^®, call the BCG office on (03) 5492 2787 or email info@bcg.org.au.