In the Great Southern region summer crops have predominantly been grown opportunistically when there is ample soil moisture post-harvest with the express purpose of filling the summer and autumn feed gap. Recently, some growers have started using summer crops to dry out waterlogged paddocks over the summer fallow period to prevent early season waterlogging in the following winter crop. However, this can be dependent on what type of summer cop has been grown, and how it is managed. Crops with a low water use efficiency, and produce a large leaf surface area such as forage canola tend to be more effective in removing soil moisture. Whereas a grass variety such as a millet or sorghum can actually preserve soil moisture within the fallow period, more effectively than a chemical controlled fallow, particularly when managed by grazing.
Gravimetric water content was taken at the Webb Summer cropping site prior to seeding and at the termination of the summer crop frow a specific location within the treated (millet) and the untreated (bare fallow) area. The results show that there was a higher percentage of water content within the treated zone then within the untreated. This highlights the ability for the millet to preserve soil moisture over the summer period, compared to a bare fallow. This is likely a result of the millet providing ground cover that reduces evaporation from the soil, coupled with the high water use efficiency of the millet, particularly after it has had a lot of the leaf area removed by grazing. Additionally the summer crop will increase the soils infiltration rate, allowing the soil to recharge more efficiently when summer rains fall, particularly on soils where non-wetting issues are prevalent.
