Jeremy Lush remembers when he first assessed the soils at his family’s newly acquired property near Sherwood in South Australia’s south-east it “felt like Christmas”.
Although compacted after carrying a heavy livestock load, the clay in the soil profile offered a far greater potential than the water-repellent, deep sand-on-limestone characteristics of his childhood farm, west of Sherwood at Keith.
The then 21-year-old, with his father Rodney, immediately set a path for continual improvement, ameliorating soils and starting a rotation to build carbon and other nutrients.
Five years later, in 2024, they are trialling lentils for the first time – part of a plan to increase diversity of rotation on the 450-hectare site from four crops (beans/wheat/canola/barley) to six by including two legume crops over six years. Economic analysis has shown that even if they do not yield well, lentils should return a greater margin than canola, Jeremy says. They also help spread risk and provide more market opportunities.
We know we can grow legumes profitably with good agronomy, but I’m starting to understand the flow-on benefits in terms of residual nitrogen and the value not just in the following year, but also in subsequent years, Jeremy says.
He says the importance of providing adequate nutrition to his ameliorated soils is one of most valuable insights he has gained from amelioration research underway at a nearby property.
Managed by Dr Melissa Fraser from Soil Function Consulting, the three-year GRDC and SARDI investment with Mackillop Farm Management Group is looking to minimise risks and improve and sustain soil productivity after amelioration. Jeremy says the research has demonstrated the importance of feeding a crop appropriately post-amelioration to meet its increased productive capacity.
Collaborating with Dr Fraser, and learning from the amelioration trials, Jeremy is increasingly using a zone-based approach to target inputs and meet yield potential in different parts of the paddock.
Introducing a second legume (such as lentils or vetch) into the rotation would help to feed productive areas with extra nitrogen without increasing their spend on urea, he says. “We’re big advocates for cost control, but not at the expense of productivity. So two legumes in six years allows us to manage the cost but still have the nitrogen available for us to capitalise on in a good year.”
This year, after detecting some acidic zones, he has also moved to an acid-tolerant rhizobia to improve nitrogen fixation. “We’ve identified a few things that will reduce risk from an expense point of view,” he says. “If we use acid-tolerant rhizobia, there will be more nitrogen from nitrogen-fixation available to the following crop, so there is a flow-on effect.”
Jeremy hopes that building carbon following amelioration will not only support yield increases in the short term, but also build sustainability of the soils and the cropping program into the future. “When you add clay into the mix you really change the dynamic of the soil and what it can do, so we’re trying to take advantage of that and build resilience into our business.”
More information: Amplifying the impact of amelioration