INNOVATIVE CARBON STORAGE AND NITROGEN MANAGEMENT STRATEGIES IN THE wa WHEATBELT
This project has two main aims:
Reduce nitrous oxide emissions
The project will trial and demonstrate innovative on-farm practices that can reduce nitrous oxide emissions, through the rotational use of leguminous crops to reduce the use of nitrogenous based fertilisers whilst maximising net primary production (biomass).
Increase carbon stored in soil
The project will trial and demonstrate innovative on-farm practices that can increase the sequestration of carbon in soil, through the use of biochar, soil amendments, biological amendments, and use of additional composting materials to develop economically viable farming practices that sustainably build and store soil carbon.
Project lead organisation
University of Western Australia (UWA)
The project will trial and demonstrate on-farm practices to reduce nitrous oxide emissions and increase sequestration of soil carbon through the rotational use of legumes and the addition of soil amendments (including biochar, compost, manure, and biological amendments) on paired sites on nine cropping and grazing farms throughout the Western Australian wheatbelt.
Carbon (C) is an important part of maintaining soil health and the productivity of the soil. It provides an energy source for many functions considered important for soil biological health, including the transformation of nutrients to more plant available forms, increasing soil pH buffering capacity, increasing cation exchange capacity, stabilisation of soil structure, and the degradation of soil pollutants.
Building soil carbon is a product of soil type, climate, and management factors. The soil organic content that can be achieved depends not only on the potential of the soil to protect C but also on the productivity of the crop or pasture. Theoretically, there is a soil carbon upper and lower limit in all soils. Previous research conducted by the Liebe Group show that in the low rainfall environment in the Northern Wheatbelt of Western Australia, the upper and lower limits of soil carbon will reach an equilibrium over time, that is where the microbial decomposition of organic carbon is lower (upper limit) or higher (lower limit) than the input of new carbon inputs.
The challenge for our farming system is to find methods to push our current carbon storage equilibrium more towards the upper limit and thus the soils potential and keep it at that current equilibrium.
Hoyle, Baldock & Murphy (2009), indicate that there a number of management options for farmers to sequester soil carbon, centring around increasing inputs of soil C, improving soil structure, and supplying adequate amounts of nutrients to the soil.
This project aims to demonstrate practices that cover all three of these areas. In the area of addition of soil C, growing more biomass such as perennial pastures, eliminating fallow, or adding biochar to the soil all present a viable way to add soil C.
Improving soil structure, through improved stubble management and reduced wind erosion achieved by cover cropping, decreases loss of organic residues from the soil, and thus the loss of soil C, from the soil.
Thirdly, by supplying nutrients through brown manuring crops, utilising the N-fixing ability of leguminous crops and adding organic soil amendments ensures crop biomass and root growth is maximised, thus increasing the C in the soil. As organic materials decompose, nutrients can be released (mineralised) or taken up (immobilised) by soil organisms.
Increased capture of CO2 from the atmosphere through increased rates of photosynthesis contributes to C sequestration through the return of plant residues, root exudates, and root biomass to the soil. Some of this C will return to the atmosphere as CO2 through biological decomposition but a component is likely to be sequestered within the more stable fractions of SOC that are resistant to biological decomposition.
Therefore C losses (i.e. CO2 into the atmosphere) can be reduced by increased movement of C into stable SOC pools or the microbial population. This could be achieved by increasing plant growth (and the amount of photosynthetically-fixed CO2) or through improved agronomic and soil management options that reduce losses through decomposition and erosion.
The Liebe Group has a strong history in research, development, extension, and validation of agricultural practices that improve the economic, environmental, and social aspects to a farm business.
The group has taken a lead role in soil carbon & biology research at a paddock level and has a 10 year, long-term trial that is demonstrating the upper and lower limits of carbon storage in our soils. This research has been conducted with UWA who have strongly backed and provided technical support to this project over the past 10 years.
Impact of rotation on fertiliser efficiency and nitrous oxide emissions: Trial at Dalwallinu
Locally referred to by growers as the practice for profit trial the heavy clay site has been home to this trial since 2010. Four different crop types are compared (canola, wheat, field peas and volunteer pasture) in different rotations. Over top of the crop types, high and low fertiliser regimes are compared to see which combination has the least nitrous oxide emissions.
Testing the forage shrub Tedera: Trial at Watheroo
Tedera, a drought tolerant legume, has shown an excellent ability to produce sheep feed over summer on good yellow sand at the Liebe Groups’ Buntine site. However, this project is now testing the plants ability to grow on the poorer quality land which is unsuitable for cropping. If the plants can be successfully grown it will be of great benefit to farmers by producing sheep feed over autumn when there is no other feed around. The group also expects the root system of Tedera will increase carbon storage in areas of soil where other plants will not grow. Seedlings were planted in August 2013.
Bentonite clay incorporation for increasing production on sandy soil: Trial at North Miling
Here we are investigating if increasing the clay content of a soil by adding a soil amendment (bentonite clay) will increase biomass production, which in turn will increase soil C.
Using cereal rye to increase soil carbon: Trial at Wubin
This patch of soil became so windblown and low in C that it would not grow conventional crops like wheat, so the Liebe Group and local farmers tried cereal rye. This deep rooted, drought-tolerant plant is on its way to increasing soil carbon.
Can mouldboard ploughing increase soil carbon storage by ameliorating soil constraints?: Trial at Buntine
We hypothesize that by creating a soil free of constraints, such as acidity and compaction, crop roots will be able to grow more extensively and thus store more carbon in the soil. This trial compares the effectiveness of a mouldboard plough and deep ripper in ameliorating these constraints.
Biochar: Trial at Buntine
Biochar, the by-product of using organic matter such as old mallee’s for electricity generation, has potential as a carbon storage method. In this trial we add 4t/ha of biochar to a deep yellow sand and are awaiting the results.
Brown maturing: Trial at Buntine
In this trial we returned our 2012 canola crop to the soil using offset disks to see if the economic benefits of increased nutrition, weed control, and carbon storage in future years outweigh the loss of grain income in 2012.
Results and Reports