Mr Glenn Mcdonald1, Mr Grey Poulish1
1DPIRD, Albany, Australia
Biography:
Glenn is a research scientist with the Department of Primary Industries and Regional Development. He has more than 25 years’ experience in crop agronomy and physiology research including soil amelioration, waterlogging, drought and oats as well as a stint as a grower group facilitator. Glenn and his family live in Albany and he works throughout the South Coast and Great Southern as part of DPIRD’s “Soil Reengineering” project.
Abstract:
Gravelly duplex soils cover a large proportion of the southern WA grain growing areas. These soils often have multiple soil constraints including soil water repellence, low nutrient and water holding, compaction and transient waterlogging. The effects of subsoil amelioration on these soils are poorly understood with growers actively seeking amelioration options.
This research aimed to determine the potential advantage of mixing subsoil clay into the shallower soil layers and improved nutrition to enhance crop performance.
This experiment utilised a long-term soil water repellence site that had previously showed inversion tillage consistently higher yielding than other treatments. In 2020 the site was bulk sown after which new treatments were imposed in 2021 that included deep ripping and additional nitrogen and the experiment was sown to canola.
The deep ripping to 550 mm increased yield on average by 0.3 t/ha and the extra nitrogen applied before sowing increased yield by 0.2 t/ha. Where deep ripping and extra nitrogen were both applied, the yield was more than 0.5 t/ha greater on average than the unripped treatments with the recommended fertiliser application (no extra nitrogen).
All unripped treatments had some yield response to the extra nitrogen that was applied, but this effect was much less consistent when ripping was applied.
This duplex soil is typical of many other locations in the region and the deep ripping at this site shows that mixing suitable subsoil clay into shallower soil layers can improve yield more than increasing nitrogen inputs alone.