In Wimmera and Mallee farming systems stubbles and crop residues provide a valuable nutritional source for sheep and lambs, and if managed appropriately, grazing need not compromise a no-till cropping system.
Research has shown that providing a minimum of 50-70 per cent groundcover, grazing crops does not have a negative impact on summer fallow efficiency or subsequent crop yield.
BCG trial work, carried out in a low rainfall environment on both a clay and sand soil-type found that grazing stubbles over the summer fallow period in a southern Mallee environment does not have negative effects on stored soil water, weed seed burial or crop growth the following season.
These results were supported by NSW research which showed that putting sheep onto stubble need not affect subsequent crops if managed carefully. It was found that stubble grazing can be sustained over summer provided ground cover is not reduced to less than 2t/ha of standing stubble or 70 per cent cover.
Grazing a cereal stubble also won’t compromise soil organic carbon accumulation as significant (uneconomic) levels of added nutrition are required to achieve the required activity and growth of microbes for optimal mineralisation.
This is positive news for growers who can now confidently make use of crop stubbles without fear of suffering any significant yield penalty in the following season.
However, it should be remembered that to avoid any negative effects from grazing stubble both the paddock and sheep need regular monitoring.
From an animal health perspective, it is important to understand that nutrition predominantly comes from spilt grain and green pick, as opposed to the straw and stubble and the nutritional value of the stubble will decline once the grain has been consumed.
The findings from a Mallee CMA project which involved tracking sheep grazing behavior at Nandaly (using GPS tracking collars) showed that while sheep preferred to spend more time on higher sandy areas, they utilised the paddock evenly while spilt grain was present.
University of New England precision agriculture specialist Mark Trotter, who led the project, in partnership with BCG and Mallee Sustainable Farming (MSF), said that when spilt grain ran out sheep tended to spend less time grazing. This coincided with grain counts falling below 40kg grain/ha – a similar result to that found in southern Victoria when cattle grazing cereal stubbles started to lose weight when grain fell below approximately 40kg/ha.
On a practical level, livestock consultant Hamish Dickinson (AgriPartner Consulting) said for the best results, producers planning to graze stubbles should plan ahead, but also have the ability to be flexible according to the season.
“It is important to align the feed with the requirements of the animal … each type (pregnant ewes, weaner lambs etc.) will have different nutritional needs,” he said.
In his ‘Five steps to successful stubble grazing’ article, which was published by MLA (16/10/16), Mr Dickson listed a number of tools producers could use to work out the nutrition needs of their stock, create a feed budget and appropriately monitor sheep.
