Stubble grazing no problem with no-till
GroundCover™ Supplement Issue: 113 | 03 Nov 2014 | Author: Ken Flower
Grazing and no-till can get along fine with careful management
Light summer grazing of stubbles in no-till systems has little impact on soil health or subsequent crop yields, according to recent research in Western Australia as part of the Grain & Graze 2 program.
Full retention of crop residues is a common recommendation of no-tillage systems and has been one of the major constraints to full adoption of the system by some growers who maintain livestock.
A four-year project carried out by the University of Western Australia – in conjunction with the WA No-Tillage Farmers Association (WANTFA) in Cunderdin/Meckering and the Facey Group in the Wickepin area – examined the impact of summer grazing on soil health and subsequent crop yields on a range of soil types, including red sandy clay loam, sand over grey clay loam, sandy gravel and sand over gravel loam.
Generally, relatively light grazing occurred at all sites over the summer periods, with stocking rates ranging from 2.3 to 5.1 dry sheep equivalents (DSE) per hectare and grazing intensity from 112 to 357 DSE days per hectare.
The stubble paddocks were either sown to crops following the summer stubble grazing or returned to pasture. Light grazing of stubble over summer had no significant effect on following crop yields compared with ungrazed stubble plots. There were no differences in soil bulk density, infiltration rate or soil water (measured before sowing) at any of the sites.
In 2012 only one grazed paddock yielded significantly less than the ungrazed plots. This paddock was grazed over both summer and winter and had heavy clay subsoil. The bulk density increased and infiltration decreased in this paddock following grazing.
There were few differences in soil chemical components between the grazed and ungrazed plots except at the Meckering sites, where the ungrazed plots had higher levels of mineral and total nitrogen. The higher nitrogen at these sites was thought to result from increased growth of the pasture legumes in the ungrazed plots.
Generally, grazing was light and resulted in no significant differences in the amount of crop residue remaining in autumn between the grazed and ungrazed plots; the exception was paddocks kept in pasture over the winter as well, in which the grazed plots had significantly less crop residue. Light grazing over summer resulted in more than 50 per cent ground cover and had no impact on subsequent crop yield. The main impact of the light grazing was to loosen and flatten the stubble residue. In contrast, the stubble in ungrazed plots was left standing in the crop rows.
The results suggest that light grazing of crop residues over summer has negligible effect on soil health, ground cover and subsequent grain yields.
More information:Dr Ken Flower, School of Plant Biology, University of Western Australia,
08 6488 4576,
GRDC Project Code FGI00007
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