Cool Soil Initiative
Cool Soil Initiative
Addressing soil carbon with Peter Campbell
Our cropping rotation is flexible. Generally, we start with a pasture phase, followed by canola followed by wheat, then barley, oats, triticale, narrow leaf lupins or arrowleaf clover. We rarely have two consecutive wheat crops and try to put a pulse in the middle of the 5-year cropping rotation.
We try to retain our stubbles 100% across the farm. This year was the first year in 20 years that we had to burn paddocks because of the large stubble load and high moisture in the soil. If we didn’t burn, then we would have had yield penalties and possibly would not have been able to sow in some paddocks due to how wet they were. Although we try to keep our stubbles and sow through them you must be flexible in your approach.
Riverine Plains
Peter Campbell
I have sown faba beans and albus lupins but found the grain yield to be unreliable so now we stick to narrow leaf lupins. The benefits of growing a pulse include providing a disease break and lower costs through not having to apply nitrogen and sometimes phosphorous. We use an aerial seeded clover such as arrowleaf in the middle of the cropping phase for a disease break and nitrogen input.
We run a mixed farm with sheep and cropping over 1200ha. We currently have around 2800 breeding merino ewes and 2000 lambs.
We have a pasture phase of 7-10 years in paddocks. Generally, the paddocks with poor draining soil types stay in pasture longer than those that drain more freely. We use a lucerne sub-clover mix on the free draining soils and either phalaris or tall fescue and sub-clover on the poorly drained soils.
Our aim is to have 2 to 2.5% carbon in our soils. Some paddocks have over 3% carbon.
There seems to be variation again based on soil types. The poorly drained soil average around 2.2% carbon in the top 10cm, possibly due to a longer pasture phase, with the better soil types struggling to reach 2%, again possibly because of more intensive cropping regime.
When testing it is important to sample at the same GPS point each time and at the same time of year to allow a fair comparison.
Maintaining and improving our soil carbon levels is very valuable to us. It is important as high carbon levels are linked with good soil fertility and allows us to reduce our nitrogen fertiliser use.
We preserve and increase our soil carbon through stubble retention, through having a zero-tillage system and using pastures in our rotation.
Healthy pastures need healthy soils and lime is a critical component to correct acidity.
We could currently put fertiliser on cereal stubbles to prevent the tie-up of nitrogen while the stubbles are being broken down, however for us I don’t feel like it is a financially viable option.
I was a bit disappointed with our soil test results as we were only around the mid-range of values.
It will be interesting to see if they are different when we test again as there are some anomalies compared to our regular soil testing programme.
From the Initiative, I would like to see a methodology developed for Australian farmers around how we can market and sell our carbon.
We have tried companion cropping forage radish with winter cereals for grazing. We didn’t identify any real benefit for soil health however radish provides good nutritional value for the sheep when combined with a cereal.
I am interested in cover crops however sceptical about the benefits to the soil compared to simply retaining stubbles, which provides biota habitat and protection from erosion.
No, not specifically. We have planted thousands of trees on our farm which I believe helps reduce the GHG emissions.
Not burning stubbles will help too. It is hard to reduce livestock emissions especially when they are out in a paddock and not in a feedlot as you can’t control their diet.
Yes, we are flexible in our approach depending on how the season is going. 2022 is the first year over a 20-year period we have had to burn a number of stubbles.
To prevent nitrogen volatilization, we avoid spreading urea onto waterlogged soils and we don’t apply it in the summer months. Like most growers we tend to wait until there is a strong forecast for rain before we apply any fertilizer.