By Susan Hall
A visiting US agricultural researcher has urged Australian R&D corporations to invest in researching ground cover crops after seeing the quick dividends they paid in Australian soils.
Professor Perry Miller, a keynote speaker at the GRDC-supported 2004 WA No-Tillage Farmers Association"s New Frontiers Conference earlier this year, said he was surprised at the rapid payback in productivity from brown manure or "ground cover" crops in WA.
“We typically must wait five or six years to see a shift in soil quality associated with ground cover crops,” he said.
“Rotational benefits from pulse crops are primarily associated with soil nitrogen dynamics, rather than soil water.”
He said it appeared that the function of soil organic matter was even more critical in some Australian soils, particularly in the WA wheatbelt, than in the northern Great Plains of North America.
“If I held the purse strings to your research budget, I"d invest aggressively in understanding the role of ground cover crops, as it seems to offer a much quicker payback here.”
Professor Miller"s US work looked at rotational benefits and the long-term effects of diverse rotations on things such as soil nutrient dynamics and soil carbon sequestration.
He found greater crop diversity paid off by delivering real dividends. “All cropping systems must increase rotational diversity if they are to overcome sustainability issues,” he said.
“Concerns with rising groundwater, soil salinity, soil organic matter and soil health can all be addressed through prudent use of plant species.”
Soil water balance can be affected by the rooting depth of crops that may impact on the yield of subsequent crops, according to Professor Miller.
“This is important in the northern Great Plains, but will have to be studied in context. Australia"s old soils are very different from our young soils.”
He proposed WA growers in particular look beyond their traditional grain crops of wheat, barley and canola.
“Diversified cropping systems have increased rapidly in Canada and have the potential to do the same in other semi-arid regions,” Professor Miller said.
“Therefore, it is important to understand how flexibility in cropping systems is increased by including broadleaf crops. Importantly, a grain yield advantage for no-tillage over conventional grain production systems occurs in diversified crop rotations containing broadleaf crops.”
Professor Miller was concerned about the lack of perennials in Australian cropping systems.
He said the problem with continuous cropping of annuals was that they did not use enough water: “Growers need to look at other options, including deep-rooted annual crops such as sunflower and find ways to get perennial plants back into the system. Growers should consider using deep-rooted crops to draw down watertables, especially where salinity is a concern.
“Trees are difficult to put back in the system, but perennial forages seem to have an obvious and historical fit.”
Professor Miller said he was impressed with the productivity gained from the very low quality soils of WA, but also very concerned about their sustainability. “WA soils are far more fragile than almost any soil types we have in the northern Great Plains.”
For more information:
Professor Perry Miller, 0011 1 406 994 5431, firstname.lastname@example.org
GRDC Research code: WAN 00006, program 6