There’s been a growing interest in cover crops over the last few years particularly in regenerative farming circles with people like Gabe Brown showcasing their work on YouTube. But do they have a fit in the Australian broadacre context?
A cover crop is a crop that is grown solely for the purpose of providing ground cover and/or building soil structure. Sometimes they are a single species but often they are thought of as a mixture of species each preforming a different role in the mix. For example a mix might contain a grass species like oats for cover, a tap rooted plant like tillage radish to improve soil structure and a legume like field pea to add nitrogen. However I believe that in the Australian context a we are suited to a straight grass type single species cover crop.
This is because we essentially a moisture driven system with our yields coming from being able to effectively store and utilise soil moisture turning it into grain yield. So we are getting our most bang for buck by effectively covering the soil and increasing our fallow efficiency. This is because your grass/cereal type species are high in lignin and are therefore slower to break down meaning they’ll cover the ground for longer and if you select the right variety it’ll be quick growing producing a heap of biomass in a short period of time. If there’s legumes in the mix they’ll increase nitrogen to carbon ratio which will speed up the break down of the cover crop.
I think cover crops have their best fit in a long fallow situation behind a crop that doesn’t leave a heap of stubble like cotton, sunflowers, chickpeas, or canola. This will help to build ground cover while also providing plenty of time to replenish the moisture in the fallow used to grow the cover crop.
However I’d like to see more research done on the long term effects of continued cover crop use and the use of cover crops in short fallow systems. As there is still a lot to learn on how they fit in the Australian farming system.