SOILS Research

What are the physical and chemical requirements for sustainable and profitable agricultural production systems on shallow peat?

To answer this question, the soils researchers are seeking to understand the effect of peatland restoration practices on peat characteristics and water dynamics. Peat soil is highly heterogenic in terms of humification, vegetation type and fire history, and these factors all affect soil properties which, in turn, affect how best to restore peatland ecosystems. The physical and chemical nature of peat changes over time, and this has ramifications in terms of possible future land use, affecting suitability for conservation, mixed use or plantations.

The effects of peat fire on soil physical properties depend on a variety of variables, including the level of peat humification and the extent of fire in terms of fire frequency and intensity. Fire frequency, area, and intensity, all affect peat nutrient availability as well, such that intense fire regimes result in lower nutrient availability compared to less intense fire regimes. Such information is important when considering ways and means of restoring peatland areas affected by fire.

Physical soil properties may change, such as the capacity to absorb and hold water following fire, or as a result of compaction or degradation. Thus, understanding how soil and water dynamics change as peatlands dry and rewet will inform restoration and revegetation practices and assist in transitioning men’s and women’s livelihoods on rewetted peatlands. For example, in Central Kalimantan, excessive deforestation and drainage in the Mega Rice Project area have impaired peatland water retention and absorption properties, and have resulted in increased flooding during the rainy season.

Chemical soil properties may also change over time, affecting factors such as nutrient availability, and acidity. Slash and burn farmers believe that the ash generated will improve soil pH and fertility. Indeed, burning peat soils can produce free minerals from ash rich in organic carbon, magnesium, potassium, phosphorus and sodium. However, this nutrient increase declines rapidly by leaching during rainy seasons.

To date, our soils research has focused on capacity building around soil sampling, soil physics and soil and water chemistry as well as scientific writing and data analysis. The team has been building human and infrastructure capital to objectively quantify the soil and water properties of peat soils and the effect of peatland restoration practices on peat characteristics and water dynamics. Capacity building workshops have focused on building knowledge and practical skills of the research team around soil sampling, soil physical properties and soil chemistry, within the research team. The outputs developed by this component will help decision-makers in selecting the most locally-suitable restoration approaches and are intended for use primarily by those government agencies that have important responsibilities for monitoring the success of peatland restoration.

Peatlands also accumulate millennia-old carbon in the form of organic soil matter. Estimating carbon emissions from peatlands requires a consistent definition of peat, knowledge of peat thickness, peat volume and peat bulk density. In this component, Dr Liubov Volkova of the University of Melbourne is working with stakeholders and the Government of Indonesia to improve the knowledge base of parameters for calculating greenhouse gas emissions from peat fires in increasingly degraded peatland areas. This work will enable the government to include peat fire emissions in their international reporting to the UN Framework Convention on Climate Change and claim emission reduction benefits over time.

Peatland restoration efforts in Indonesia are progressing rapidly, but the success of these efforts is often low or undocumented. Two techniques trialled in previous ACIAR projects – eddy covariance flux towers and chameleon sensors – demonstrated their strong potential as tools to empower government and communities to monitor and help manage peatland restoration. These techniques monitor changes to peat moisture levels and carbon and methane flux from the ecosystem. A further small research activity, led by Dr Samantha Grover of RMIT University, is using this data to work with communities, government agencies and other stakeholders to provide valuable information that supports decision-making in peatland restoration and fire management. Stakeholder engagement, which has already commenced, is a major focus of this activity.