IT'S A simple enough concept — if farmers have a weed problem, one control option is to increase the crop seeding rate; this, in turn, increases the number of crop plants in the paddock placing pressure on the weeds.
Simple! Weed numbers are lower, crop yields are higher and less weed seed is produced. But many farmers believe that, at higher seeding rates, the crop plants could become stressed and a higher proportion of shrivelled lower-priced grain (screenings) could be produced.
Research is showing, however, that there is no direct relationship between higher seeding rates and more screenings.
The Cooperative Research Centre (CRC) for Australian Weed Management at two sites in SA looked at wheat seeding rates, weed suppression and grain yield.
"One part of the study at Roseworthy showed significant reductions in annual ryegrass survival at wheat seeding rates of 100 kg/ha and above," the CRC's Gurjeet Gill said. "There was also a large reduction in the number of wild oat heads produced."
Overall, the research in the lower and mid-north areas of SA showed that doubling the wheat seeding rate in these regions from 50 kg/ha to 100 kg/ha can reduce ryegrass growth and seed production by about 50 per cent, and this is often accompanied by higher yields.
"Other than herbicide application, increased crop density is probably the most effective method of reducing weed competition and should be seriously considered for all potentially weedy paddocks going into wheat production," said Dr Gill.
Program 3 Contact: Dr Gurjeet Gill 08 8303 4455