DPIRD researchers teamed up with consultancy Integrity Ag in 2020 to develop a carbon emissions footprint for the DPIRD Katanning Research Facility (KRF), a mixed farm that produces grain and sheep products. The analysis takes into account all farm emissions plus upsteam emissions such as the manufacture of agrichemicals, and the production of purchased livestock.
Based on this information, the team developed an emissions reduction strategy to enable the farm to be carbon neutral by 2030.
KRF comprises 2100 ha, of which 1700 ha is arable and the remaining 400 ha mainly natural vegetation with saline gullies and some tree plantings.
Approximately 50% of the arable area is cropped in any one year, employing a year-in, year-out rotation with pasture. The total sheep number in 2020 was 8000 dry sheep equivalents (DSE), with an annual stocking rate of just under 5 DSE/ha recorded in 2018.
Total emissions for KRF averaged 2480t of CO2-e (carbon dioxide equivalents) per year over 2018 and 2019, excluding changes in soil and vegetation carbon. Most emissions (61%) came from sheep enteric methane. Note that KRF emissions are higher than comparable farms due to the sheep flock being part of ongoing research projects.
Reducing crop emissions
Options identified to reduce emissions from cropping revolve around a reduction in nitrogen fertilisers (to reduce the increased risk of nitrous oxide emissions and the upstream emissions from fertiliser production). While improving the legume component of crops and pastures was an obvious focus, it is notable that the team also looked at addressing inefficiencies such as limiting production of low-yielding crops or switching from low-energy to high-energy fodder crops.
Yields for both canola and lupins tend to be relatively low at KRF. Growing less canola (except where required for strategic weed and pest control) can reduce nitrogen use but leads to reduced cashflow. Likewise, lupin yields are not carbon efficient, but less production of lupins would require off-farm purchase to maintain protein levels in young livestock.
More gains could be made by using higher energy fodder crops. KRF plan to replace oat crops with barley, which have a higher energy content compared to oats. At equivalent yields, less barley would need to be grown to match the energy in feed from oats, potentially facilitating longer pasture and shorter crop phases and reducing the need for fertiliser nitrogen.
Similarly, the quality of hay produced at KRF is low, and growing less would reduce fertiliser nitrogen.
Other potential strategies include improving weed control, resulting in an increase in yield and reducing the amount of crop that needs to be grown so that longer rotations can be used. Tools to achieve this include better rotation and harvest weed management.
Another strategy is to acquire more efficient machinery to reduce diesel emissions.
Nitrous oxide emissions can be reduced by preventing waterlogging, but this can be expensive. Using nitrification inhibitors can increase nitrogen use efficiency, while dealing with soil compaction may also address the problem.
All of the strategies for reducing emissions from cropping are contingent on sheep numbers not increasing because stock produce more emissions than crop.
Reducing livestock emissions
Enteric methane is easily the largest greenhouse gas emission at KRF, and this is also likely to be the case for most mixed farmers. Enteric methane emissions are calculated from the number of animals, class of animals, and an estimate of their feed quality.
Options to reduce enteric methane identified by KRF include:
- Reducing stocking rates – but obviously reduces income
- Introducing anti-methanogenic legumes e.g. Biserrula – but potentially lowers yield compared to other legumes
- Introducing anti-methanogenic feed additives – 3NOP, Asparagopsis, which are not yet available but expected to become commercial before 2030, and
- Breeding low methane sheep that eat less per unit of weight gain.
The benefits of reducing sheep numbers were outlined as:
- reduced supplementary feed,
- more opportunities to defer grazing at the break of season,
- a greater focus on reproductive rate and weaning weights, and
- an opportunity to renovate annual pastures and improve pasture growth rates.
Pasture management and soil carbon sequestration
For soil organic carbon levels to be maintained or increased, management should focus on increasing pasture yields, longer pasture phases and reducing soil loss through erosion. This needs to occur in a future climate predicted to have lower rainfall in winter and spring.
While declining rainfall could reduce the pasture production, KRF currently produces only 57% of its potential pasture yield, while the most efficient farms produce 80%. The research team estimates that yields could be increased by 1-1.5t DM/ha/yr (dry matter per hectare per year) by addressing soil acidity and fertility, re-sowing degraded pastures with more productive species, increasing legume content and managing grazing and stocking rates.
Increasing legume content to add more nitrogen without using fertilisers, as explained earlier, could also reduce enteric methane production because the rate of digestion is increased. However, the team notes that legumes are susceptible to false breaks, slow growth rates and lower carrying capacity.
Shrubs such as Eremophila glabra have also been shown to reduce methane, but come with an opportunity cost during establishment.
The team also considered other options to increase soil carbon, including biochar, green manuring and using perennial pastures (note that direct carbon increase from biochar is not an eligible activity under an ERF methodology).
As mentioned, preventing wind and water erosion is a vital strategy to prevent loss of soil carbon, emphasising the importance of managing grazing to maintain adequate groundcover.
Note the analysis estimated that soil carbon sequestration would account for only up to 6.5% of KRF emissions and that is more likely be around 4% or less.
Vegetation in the form or windbreaks, shelterbelts or shelter paddocks (distributed shelter) can also reduce erosion risk, providing shade and shelter. Shelter is an important factor in preventing lamb loss during lambing if wind chill is high. In addition, vegetation offers carbon sequestration potential and can increase biodiversity and canola pollinators.
Carbon sequestration is obviously greater for trees, but shrubs can also achieve this to a lesser extent, as shown in a recent study using saltbush, although the study did not observe soil carbon increases. In addition, saltbush also offers an edible shelter. Tagasaste is another option, more suitable for deep sands. Both saltbush and tagasaste also retard fires.
However, while the smaller Eremophila shrubs can reduce methane emissions from livestock, some research has suggested that saltbush increases methane production from sheep.
Other benefits from trees and shrubs are that they can both lower saline water tables and slow down fast-moving grass fires.
KRF modelled several scenarios using different options described above to achieve carbon neutrality by 2030.
Being a research facility, there is more flexibility to reduce stock numbers and plant significant areas to trees. However, they acknowledge that “this approach is not an option for many commercial sheep producers and has implications for the sustainability of the state sheep flock and export markets.”
Their “best bet” scenario involves a reduction in the flock to 85%, a reduction in cropping area of 50% and implementing a 3:1 pasture to crop rotation, which is achievable due to the lower flock numbers and reduced demand for supplementary feed. These changes would enable them to renovate pastures and establish permanent pastures on non-arable or low production arable land.
The ‘best bet” scenario relies heavily on Asparagopsis to substantially reduce methane emissions from livestock and requires planting 70ha of permanent pastures, 117 ha of saltbush and 20% to trees. Other requirements include increasing flock efficiency, applying biochar, green manuring, and changing crop type to barley.
If methane inhibitors don’t become commercial soon, the team estimate that they would need to plant about 580 hectares of permanent tree plantations on arable land.
Recommendations from the team include:
- Conduct a full soil salinity survey and radiometric survey of KRF farm to inform planning of strategic revegetation and suitable areas for permanent pastures.
- Develop a remnant vegetation and a revegetation management plan for new tree and shrub plantings that satisfy the needs for salinity management, carbon mitigation, amenity, and shade and shelter.
- Establish five long-term monitoring points for soil carbon to monitor changes resulting from implementation to 2030 and 2050.
- Investigate opportunities to trial delivery mechanisms for Asparagopsis in supplementary feed utilising the Feed Efficiency Facility at KRF.
- Identify opportunities to reduce the services footprint, including photovoltaics and machinery replacement plans.
- Focus on pasture renovation and shrub systems at the facility to provide a living demonstration of modern feed base in a drying climate.
- Track the transition costs (cash flow) of all the interventions (e.g. STEP model analysis) to look at the impact(s) on farm profitability as the system evolves.
For more information or to access the report, follow this link.
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