Grains Research and Development Corporation (GRDC) trials in the north are answering growers’ questions about stubble management in no-till and zero-till controlled traffic farming systems in southern NSW.
Part of the GRDC flagship stubble initiative, Maintaining Profitable Farming Systems with Retained Stubble, the past six years of trials conducted by FarmLink Research and CSIRO at Temora have shown that grazing and retaining stubble (not burning) is the most profitable treatment, conserving water, speeding up nitrogen (N) cycling and reducing N tie-up by the stubble.
Outgoing research lead and La Trobe University lecturer Dr James Hunt says when the amount of N available is dictating the yield they’ve seen a positive change in yield and quality by manipulating the N available.
“The reason we did this trial was because farmers were wondering if the full potential of no-till and controlled traffic could be realised if sheep are grazed on cropping country,” Dr Hunt said.
“Sheep remove residue cover and trample soils, but there was little contemporary research to show what affect that might have on crop yields.
“By averaging results across the six years that the trial has run we see that the grazing and then retaining without burning stubble treatment had the highest gross income.
“Even if no value is placed on grazed stubble, the stubble-graze stubble –retain treatment still grossed $45/ha per year more than the nil graze stubble retain treatment. Assuming grazed stubble is valued as a feed source, this economic advantage can be raised to $178/ha.”
Since 2013 the trials show that the graze and retain treatment consistently delivered higher yields, whereas burning was only of benefit due to frosts in 2013 and the wet growing season of 2015.
“Burning stubble decreased the amount of water stored over the summer fallow that was used by crops by 8 – 21mm, but this didn’t always decrease yield due to frost damage, N limitation or adequate subsequent recharge,” Dr Hunt said.
“There are several benefits to mixed farming systems, including diversification, offsetting production and price risk and increasing resilience.
“Nitrogen fertilizer inputs may be able to be reduced and grain yields increased if measures are taken to ensure that stubbles are grazed thoroughly and evenly down to threshold levels.
“Our research shows that a well-managed livestock enterprise can complement conservation farming practices such as no-till seeding with stubble retention and controlled traffic to increase crop yields and water-use efficiency.”
Dr Hunt says while the results show mixed farmers can safely continue grazing stubbles under these practices, there are some basic rules that should be followed in order to avoid yield penalties.
“This includes controlling all summer weeds promptly with herbicides prior to grazing as weed control by livestock is unreliable, and not grazing below 70% ground cover to prevent water run-off and soil erosion,” he said.
“70% cover is equivalent to 2-3t/ha of cereal stubble cover, and to estimate initial stubble load, for every 1t/ha of grain yield about 1.5t/ha of cereal stubble will be left as residue.
“Ultimately the message is that grazing stubble after harvest will have benefits which far outweigh any negative effects in a well-managed mixed farming enterprise.”
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Ellen McNamara, Cox Inall Communications
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