A SA agricultural machinery research and development team is providing the engineering expertise needed to investigate soil amelioration and mitigation strategies and their impacts on soil and crop health.
Research engineers at the University of SA Agricultural Machinery Research and Design Centre are involved in a number of GRDC-funded projects that aim to tackle a range of subsoil constraints in cropping, including compaction, low nutrient status and organic matter, water repellence and chemical imbalances.
The projects are being conducted by multi-disciplinary teams involving research partners like CSIRO, PIRSA, Vic and WA agriculture departments, and key agronomy research consultants.
UniSA research engineer Jack Desbiolles said the projects investigated how to best implement the recommended agronomic strategies addressing topsoil and subsoil constraints, by evaluating and improving machinery solutions to get the best outcomes.
While seasonal rainfall often dictates how much this translates into grain yield, research is focusing on identifying the most cost-effective approaches.
"These constraints limit root development and their extractive functions leading to crops haying off early, despite significant water being available in the subsoil," he said.
"In a one-off amelioration intervention aiming to boost crop response, we look to modify the soil profile by loosening, delving, mixing, inverting and adding some organic and/or mineral amendments to redress chemical and biological constraints.
"In Vic, work done in high rainfall areas with organic manure injection achieved really good long-term responses.
"These have transformational impacts onto the soil, not just incremental improvements."
Research has particularly highlighted the opportunity to increase yields on under-performing sandy soils, according to UniSA research engineer Chris Saunders.
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"Projects focusing on sandy soils across the southern and western regions are looking at the impact of mouldboard ploughing, rotary spading and topsoil slotting techniques," Dr Saunders.
"There has been doubling and tripling of crop biomasses and lasting significant impacts.
"While seasonal rainfall often dictates how much this translates into grain yield, research is focusing on identifying the most cost-effective approaches."
Dr Saunders said another project was examining the inclusion of top layers, including surface amendment, down to depth using a concept developed in WA.
"Inclusion plates are fitted behind deep ripping tines, creating a gap to let the top layer backfill in a mix behind the tyne and creating a column of improved soil/amendment mix, which acts as a bridge between top soil and lower subsoil for roots to go down."
AMRDC research associate Dr Mustafa Ucgul explained that part of the agricultural engineering process involved computer simulation using a state of the art technique called District Element Modelling.
"DEM enables full scale machinery simulation in a soil-like environment to assess and optimise performance," he said.
"The simulation medium is made up of a bulk of discrete particles that are millimetres in size and that behave like soil.
"The particles are calibrated against measured field soil properties and key machine simulations are also validated in the field using full scale implements.
"The DEM work applied to rotary spaders showed how the soil-amendment mixing uniformity is highly dependent on forward speed.
"We are now conducting research on the link between soil-amendment mixing uniformity and crop response, contrasting lime and organic matter".
UniSA agricultural research engineer Dr James Barr, also involved in conducting DEM simulations, said the approach was revolutionising agricultural machinery development, with much of the work able to be done 24/7 on modelling stations to select design and setting optimums, which are ready to test and fine tune in the field.
Dr Barr has focused his input into modelling no-till seeding systems for optimising furrow management in non-wetting sands.
"The work has been critical in understanding the process of furrow backfill and how design and operating parameters directly influence the extent of topsoil backfill ending up in the seed zone," he said.
"This knowledge also has ramifications for optimising crop establishment in marginal moisture conditions but also how to control crop damage from pre-emergence herbicides."
"The latest trials, conducted this season on the Eyre Peninsula, have demonstrated drastic improvements in crop establishment in a highly water repellent sand, with combinations of in-furrow soil wetters, on-row sowing, inverted T openers, deep-till sowing and paired row sowing."
NEW MACHINE EXPANDS TRIAL POSSIBILITIES
TO ASSIST recent soil improvement projects, the Agricultural Machinery Research and Design Centre led the development of an amendment injection subsoiler, to test subsoil amelioration techniques in a project led by Agriculture Vic.
The machine was co-developed and manufactured by AgriBits in Adelaide and included supplied components like a liquid unit from Liquid Systems SA, belt hoppers from RiteWay Farming, ripping tines from Tilco Ag Systems and a clod-breaker roller from Kiki Engineering.
University of SA agricultural research engineer Jack Desbiolles said the AIS was a versatile machine aiming to test out a wide range of soil amelioration strategies.
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"The dual-depth tine system loosens soil to full depth and amendments are injected out of multiple hoppers into a boot section behind the deeper tines, allowing products to be applied at full depth and an adjustable intermediate depth," he said.
"The project field trial results will guide what is the most effective approach and will also guide the optimum machinery solutions down the track.
"We are trying to promote access to deeper layers through the constraint layer, as well as improving the constraint layer itself."
The AMRDC group has also developed a sowing kit to allow one-pass spade and sow operations to tackle soil erosion risks associated with deep tillage operations in fragile soils.
"Our latest approach includes modifying the spader to spade 35cm wide strips only and leaving standing stubble in between," Dr Desbiolles said.
"A strip-spade and sow operation can more safely treat a whole sandy area in two halves over two consecutive seasons so this approach is worth evaluating."