Research on a comprehensive range of deep tillage practices on sandplain soils has demonstrated the yield benefit is worth the investment.
There has been increasing interest across the Grainbelt in the use of deep rippers, mouldboard ploughs, one-way ploughs and clay delvers to manipulate the soil profile to depths of up to 70 centimetres.
Department of Primary Industries and Regional Development scientists, in collaboration with AgVivo consultant Tim Boyes, compared the performance of several strategic deep tillage options in field trials at Meckering and Goomalling, with support from the Grains Research and Development Corporation (GRDC).
The results, to be profiled at the 2018 GRDC Grains Research Update in late February, showed significant wheat yield benefits after one or two seasons.
Department soils researcher Steve Davies said good wheat yield responses were achieved across a range of deep tillage practices.
“Overall yields increased by 26-50 per cent in the first year and five-39 per cent in the second year on pale deep sand over gravel soil at Meckering, while at Goomalling yield increases to responsive treatments were two-93 per cent,” Dr Davies said.
“The most profitable treatment at Meckering over two seasons was one-way ploughing, followed by ripping with spading and soil inversion with a mouldboard plough.
“Only very deep ripping, with or without soil inclusion or with one-way ploughing, were profitable in the first year at Goomalling, which had a more difficult 2017 season with much lower yields.”
Dr Davies said the research provided a valuable insight into the complexities of the deeper soil profile.
“On the deep sand over gravel soils at Meckering, removing deep soil compaction improved the plant’s root access to potassium, nitrogen and water, which drove improved productivity in the first year,” he said.
“More sustained yield responses in year two were achieved by treatments with additional topsoil and subsoil modification, such as deep mixing with a spader or inversion with a one-way or mouldboard, which effectively removed the topsoil water repellence.
“At Goomalling, the removal of deep compaction, particularly in the dry season, improved root access to subsoil moisture, subsequently improving yields and the removal of water repellence achieved better crop establishment.”
The research also included an economic analysis of the investment, which demonstrated cost recovery from most treatments could be achieved within two years, apart from delving which has a higher initial implementation cost.
“Many treatments recover their costs in the first year, although this depends on the site,” Dr Davies said.
“The economic benefit from a number of other treatments are almost as large as the cost of the treatment, so the break-even point is year two.”
Dr Davies said the data from the research would assist the development of more comprehensive agronomic packages and assist consultants and farmers to make more informed decisions to optimise the benefits of soil manipulation at depth.
“We now have a better understanding of the soil profile and the gains to be attained by tapping into moisture and nutrients below 50 centimetres, which could make a substantial difference to crop performance in particular seasons,” he said.
The field trials will continue during the 2018 growing season and complement other soil manipulation trials being conducted by DPIRD with GRDC support across the Grainbelt.
“Understanding how long these treatments continue to provide benefit for is paramount to support grower adoption,” Dr Davies said.
More details on this project and a range of other research initiatives will be showcased at the 2018 GRDC Grains Research Update on Monday, 26 and Tuesday 27 February at Crown Perth.
Further information is available on the Grain Industry Association of Western Australia’s website. [1]
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Jodie Thomson/Megan Broad, media liaison
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