GROWERS need to assess a range of amelioration activities on their properties in order to find the most appropriate method to ensure the best outcome.
Deep ripping trials, conducted across WA for the past two years, have started to clarify which soil amelioration practices increase crop production across a wide range of soil types.
The Grains Research and Development Corporation Ripper Gauge project is being conducted in conjunction with the longer-term investment 'Subsoil constraints - understanding and management'.
The West Midlands Group (WMG) is co-ordinating the Ripper Gauge project in WA in conjunction with eight other grower groups including the South East Premium Wheat Growers Association, Stirlings to Coast, Facey Group, Corrigin Farm Improvement Group, Liebe, Mingenew-Irwin Group, Southern Dirt and the Merredin and Districts Farm Improvement Group.
WMG executive officer Nathan Craig said the use of deep ripping to reduce soil compaction, mouldboard ploughing, rotary spading, and 'Plozza' ploughing to reduce soil water repellence have led to significant increases in grain yield for many growers, but not all.
"To date, much of the research has been conducted on sandy soil types that are easier to work with," Mr Craig said.
"The question has been asked by many growers of the benefit of soil amelioration on many of the other dominant soil types in each region of WA."
As part of the GRDC project, 20 demonstration sites were established across WA in 2018, from Yuna to Esperance.
The soil types tested range from loamy sands through to gravel and sand duplexes, forest gravels, and clay soil types.
Four standard treatments were tested against a control consisting of; ripping to 30 centimetres, ripping to 60cm, and a local farmer solution which often contained a combination of soil amelioration treatments.
For each of these treatments, plant growth was monitored during the season and grain yield measured using yield mapping at harvest.
Mr Craig said the results from the two years indicated that groups of soil types were generally behaving similarly to each other.
"The soil types that are described as sand, for example 'loamy sand', responded best to ripping to 60cm depth across most sites in this project and this positive benefit was largely consistent across both years," he said.
"The soils that are described as having a gravel component, for example 'sand over gravel', tended to respond best to amelioration that involved higher levels of soil disturbance, this could include an aggressive tillage machine or Plozza Plough.
"This effect was greatest in 2018, the season immediately following the amelioration being completed, but did not always follow through to the next year."
In the first year of the project, some significant management issues with amelioration activities were identified.
One issue was the large increase in weed populations where aggressive 'maximum tillage' was used, while when ripping in clay and gravel soils was scheduled, the dry season limited the effectiveness of most machines in achieving the target ripping depth.
Mr Craig said the cumulative gross return of all treatments varied considerably across treatments and sites, with 27 per cent of treatments returning negative gross returns across the two years.
"Approximately half of the treatments returned a positive gross margin, but only 28pc of treatments returned a cumulative gross return of greater than $100/ha, which is considered to cover the cost of the amelioration activity," he said.
"This result highlights the need to assess a range of amelioration activities on growers' properties in order to find the most appropriate amelioration method.
"This is particularly important for the 'other' soil types that have historically not had as much work completed compared to sandplain soils where the response to amelioration, particularly deep ripping, is well known."
The project will continue throughout 2020 and will be the final year of the trial.
