Digging out the old tools

However, he said the future of weed control looks to lie in technologies that integrate the best of chemical control – like weed detection systems – coupled with on-the-spot, strategic tilling.

Dr Widderick says what is clear from his research, which is supported by the Grains Research Development Corporation (GRDC), is that continuing to rely wholly on chemical control is not an option.

“The spread of no-till farming has meant almost all weed control now revolves around herbicides. As a result, the weed spectrum in the northern grain region has changed to favour herbicide-resistant, surface-germinating weeds like common sowthistle, fleabane and feathertop Rhodes grass,” he said.

The challenge was to identify ways of using tillage that retained the benefits of zero-till while also addressing weed management issues. Tillage presents a mixed bag of benefits and problems to grain growers. Aside from the damage it causes to soil structure, its effects differ markedly on different weed species.

He said burying seed can prevent weed germination, but it generally also preserves seed viability.

In one Queensland Department of Agriculture and Fisheries (DAF) trial, virtually all barnyard grass and liver grass seed became unviable after two years on the soil surface, but at least 10 per cent of seed survived when buried at a depth of 10 centimtres.

However, overall, Dr Widderick said tillage had the potential to reduce the emergence of all weed species compared to emergence under zero-till. Tillage treatments proved most effective on small-seeded species like fleabane and common sowthistle and the greater the tillage intensity, the lower the subsequent weed emergence across all species.