Grazing stubble benefits sheep and next season crops
GroundCover™ Issue: 122 | 02 May 2016 | Author: Toni Somes
New South Wales grower Michael Sinclair says new research has given him insight into the value of grazing livestock on crop stubble.
Stubble has always played a part in the Sinclairs’ livestock enterprise, but the family began to have concerns about the impact sheep were having on soil structure during the Millennium Drought.
So they started to either not graze stubbles, or graze them lightly. However, during the past six years their country in southern NSW has experienced productive seasons creating a greater stubble biomass.
This, coupled with GRDC-supported research has given them the courage to put livestock back on stubble. The Sinclairs also have an improved understanding of the role controlled grazing can play in a grain enterprise.
“We have always looked at stubble as a valuable resource for livestock and a way to spell our perennial pastures,” Michael says. “But we were concerned about compaction, how grazing impacted sowing and the effect on the subsequent crop.
“This research has given us a better understanding of the impact sheep have on our soil and its water harvesting ability and the potential contribution grazing can make to the following crop through nutrient cycling.
“It has also given us a few basic rules of thumb for grazing stubble without having a negative impact on weed control and subsequent moisture harvesting over the summer.”
The Sinclair family put sheep onto stubble immediately following harvest and take them out when stubble starts to deteriorate.
The exit date hinges on summer rain, which reduces the quality of the dry feed.
“We don’t like to have sheep on stubble if we get a lot of rain, due to compaction risk,” Michael says.
“If the summer is drier, the feed quality of the stubble is generally higher, so we will graze them for longer – as long as we can maintain adequate ground cover to maximise rainfall infiltration.”
Michael says grazing stubble allows the spelling of their pasture country, which is predominantly perennial species of lucerne, tall fescue and chicory. Sheep are also drenched prior to grazing stubble, providing worm-free paddocks to break the worm cycle.
“The grazing of some stubbles, particularly barley, enhances our ability to sow into those stubbles with our tyned seeder,” he says.
However, Michael says from a cropping perspective it is difficult to quantify the increases in soil nitrogen data from the trial.
“I don’t think we would be able to replicate the kind of nitrogen level and yield increase results that the trial achieved, purely because we cannot replicate the high stocking rates that the small trial paddocks had.
“So this is an area of the research project that has asked more questions than it has answered.”
Yet the upside of the research work is the emphasis it put on weed control.
“The one factor we have not compromised since we have started grazing our stubbles again has been weed control,” Michael says.
“As the research project indicated, any green leaf in a stubble paddock over summer is a source of moisture loss from the system.
“The sheep are managed around our need to keep the stubbles weed-free, and in most cases they will follow the boom spray (after withholding periods), to help control hard-to-kill weeds such as milk thistle and prickly lettuce.
“We don’t back-off our chemical rates, and we will still double-knock a paddock if we need to.”
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