A new SAGIT funded project is studying the value of spading header rows to control weeds and improve soil health.
Insight Extension for Agriculture’s Chris McDonough says previous trials in the South Australian Mallee have shown that spading organic matter into the top 40 centimetres of sandy soils can have yield and soil benefits, however this project is the first to study its practicality across a whole farming system.
“Spading has been shown to reduce ryegrass populations by 75 to 87 per cent, which is significantly higher than burning header rows, without chemicals,” Mr McDonough says.
“Spading with added nutrition can also increase yields on sands by up to two tonnes per hectare, and break up compacted soils to improve soil health and water infiltration.
“It is already clear that spading is a very useful tool but it is important that growers know whether it is practical and if the benefits justify the expense of purchasing their own machines.”
The key challenges to be studied in the project are wind erosion, the risk of tying up nutrients in the decomposing straw, the impact of varying soil types, and the effect of spading over multiple years.
The project is trialling two soil types over a three-year period the Hayward family property at Lameroo on each phase of their crop rotation. Spading 4-metre-wide header rows will be compared full spreading of straw and narrow windrow burning, with a fourth strategy of adding nutrition to the spaded header rows.
Spading and burning operations were performed this season, with monitoring to be performed over three years.
“Many growers are wary of spading because of the risk of erosion, but what we’ve seen in previous trials and what I expect to see in this trial, is that by only spading the header row we are leaving most of the stubble behind to protect against erosion,” Mr McDonough says.
“There is also the risk in cereal-on-cereal rotations of the buried straw strips tying up soil nutrients to break down the residues.
“These straw residues have been measured at 20 to 30 tonnes straw per hectare, which represents a significant organic matter addition but also a large amount of material to break down, which is why we’re including a treatment of added nutrition.”
A key aspect of the project is overcoming the practices challenges that arise when adopting new technologies. For example, in 2016 some spading brought sodic clays to the surface that reduced crop germination, meaning the spader had to be lifted in heavy soils this season.
This trial is supported by the SA Murray-Darling Basin Natural Resources Management Board, through funding from the Australian Government’s National Landcare Programme and NRM levies.