BCG with support from the Wimmera Catchment Management Authority, through funding from the Australian Government’s National Landcare Program are moving into the second year of the WCMA ‘Building Carbon and Capacity’ Project researching the relationship between soil amelioration techniques and soil carbon.
By solving soil constraints through soil amelioration BCG hopes to be able to produce more biomass which will, hopefully, lead to an increase soil carbon over time.
Soil amelioration is a term used to describe an improvement in soil structure through mechanical inputs with the primary aim of improving air and water balance within the soil. Increasing soil carbon supports increased microbial activity, provides a reservoir of organic nitrogen, phosphorus and other nutrients for plant productivity, and improves soil structure to help increase water infiltration and storage, while decreasing soil losses by wind or water erosion.
Each year the project team undertakes soil sampling from 20 or more grower paddocks which is recorded alongside rotation and management data to establish a baseline level of soil carbon across the Wimmera. This year, soil sampling is well underway with BCG staff busy conducting soil sampling on a range of properties and spoil types.
Baseline soil carbon results from sampling undertaken in 2019 in the Wimmera ranged from organic carbon levels of 0.78-1.78% in 0-10cm, with an average of 1.1%. Total carbon in the 0-10cm ranged from 0.87% to 1.89%, with an average of 1.4%.
Research plots are being sown at two trial sites in the Wimmera, one at Wal Wal (near Rupanyup) which was established in 2019 and one at Netherby (north of Nhill, south-west of Rainbow) that will be established this year. The mechanical treatments being undertaken in these trials include deep ripping, clay spreading and manure spreading at different district practice rates.
Throughout the growing season BCG will monitor and assess crop establishment and biomass. During harvest grain yield and grain quality are assessed for each treatment. Both trial sites in the Wimmera will run for four years, providing long-term data on the relationship between soil amelioration techniques and soil carbon. A normal rotation will be used, allowing BCG to understand the effect on pulses, cereals and canola.
At the annual BCG Trials Review Day earlier this year, BCG Research and Extension Officer, Kate Maddern, presented results from the trial undertaken at Rupanyup in 2019. “While the results of a single year of research need to be verified through ongoing research, we were able to identify some interesting outcomes which may be able to assist growers with their decisions” explained Kate. “Applying 20t/ha of chicken manure significantly increased yield compared to the control, by 1.3t/ha. However, the manure caused the crop to ‘hay off’ in the tight spring, decreasing grain quality” she said “ While deep ripping (~35cm in depth) and claying (200t/ha) significantly decreased crop establishment (75 plants per m2, compared to the control of 113 plants per m2). Ripping caused a significant decrease in yield, however claying did not.”
While the results may not provide a positive outcome for establishment, it shouldn’t be discounted as a solution. In relation to the operation Kate provided the following advice “If you are considering deep ripping or claying on your farm, it is important to understand which problem you are trying to fix, and to conduct the relevant soil testing first, to ensure that you aren’t making the problem worse.”
Soil Sampling is a key step in setting up your program, and to understand what actions you should take and why. It is also valuable when trying to determine what inputs you need in the current period is an important step and can help guide input decisions for growers.
“Understand your soils, understand your crop requirements and source inputs appropriately” explains James Murray, BCG’s Senior Manager Research, “Using soil data alongside a modelling tool, such as YieldProphet, can help growers match the input requirements with yield potential and ensure that farmers don’t over-invest. When supply lines are tight ensuring that you aren’t over-allocating your fertiliser per paddock is one of the most important things you can do.”
Growers who are interested in undertaking soil sampling to increase their soil knowledge are encouraged to visit the BCG website or get in touch at info@bcg.org.au for more information. Similarly BCG has recently presented a webinar on the benefits of soil sampling which can be accessed through the BCG website at www.bcg.org.au alongside other relevant information for Australian Broadacre Farmers.