After seven months, heavy, lifeless clay unearthed from under the trial of a long-season bean crop in tropical Thailand had been converted into healthy-smelling and crumbling soil filled with insect life. This happened despite the high temperatures and moisture which leads to rapid degradation of soil organic matter. The question is whether similar results can be found in Australia.
Cover crops have been shown to increase soil organic carbon which reduces soil surface strength, increases subsoil permeability and improves the soil’s water-holding capacity. This can encourage vigorous and deep root growth, which is generally associated with higher yields.
However, some studies have not seen a significant response in soil properties to cover crops, and more work needs to be done on the interactions between climate, management history and soil type.
In parts of the USA where cover cropping is a well-established practice many swear by its benefits for long-term productivity.
Trials in the high rainfall zone by Southern Farming Systems and others have shown that this region might benefit from the opportunistic use of cover crops. From the protection of the soil from sunburn and dehydration over the summer months to providing a fodder option and improving detrimental soil characteristics such as hostile subsoils, bleached layers, acid layers at depth and buckshot, that restrict plant growth, the popularity of cover cropping is increasing.
Rainfall data from 1913 to 2016 at Lake Bolac shows that on average, 25 per cent of the annual rainfall falls in December through March. Trials in 2010 – 2012 in Werneth, Winchelsea and Skipton grew a summer fodder crop followed by a winter grain crop that did not suffer any yield penalty.
It seems worthwhile to keep an eye on this research, check out a neighbour’s summer crop or even trial one of your own. Options include sunflower and sorghum, with promising results for spring-sown winter canola as a dual-purpose crop.
