Revisiting the role of soil organic matter in delivering the essential nutrients within the sugarcane cultivation regions in Australia – A landscape perspective

Summary

The project will revisit the role of soil organic matter in delivering the essential nutrients within the sugarcane cultivation regions of Australia, taking a landscape perspective. This broader perspective will provide new insights into the release of key nutrients through the mineralisation process of soil organic matter. The planned work will further explore the direct and indirect contributions of soil organic carbon and its forms, along with other crucial soil attributes and environmental drivers, in the release of these essential nutrients. This research aims to investigate these aspects using broader landscape-scale datasets that cover entire sugar production regions in Queensland. The work will also provide underpinning data for the development of rapid and cost-effective measurement and prediction of soil organic carbon stocks and potential delivery of plant-available nitrogen from mineralisation (potential mineralisable nitrogen – PMN). The outcomes of the research will provide an avenue to rethink the current broader recommendations on the estimation of PMN, leading to a more spatially explicit decision-making process. This, in turn, will reduce the input costs for inorganic fertiliser, decrease GHG emissions, and promote more sustainable farming systems.

Acknowledgement
This project is fully funded by the Department of Primary Industries and managed by Sugar Research Australia.

Objectives

Create a spatially explicit PMN, soil organic carbon, soil carbon fractions (labile vs stable), and other key soil properties such as plant available Phosphorous and Potassium measurement across key sugarcane growing regions: Currently, six broad regions are defined for PMN associated with sugar-growing soils. These regions are relatively large, and considering the spatial variability of soil attributes and functions, there is room to re-assess and gather PMN data using a spatially optimised sampling design.
Develop a comprehensive measurement database for PMN, soil organic carbon, different forms of soil carbon, and other key soil properties targeting key sugarcane growing soils: A key feature of the project’s soil database will include measured PMN and various forms of soil carbon. This new knowledge will facilitate contributions of soil organic matter to PMN, providing first-hand information to farmers and a new understanding of nutrient management on their farms.
Develop Infra-red spectral models: Predictive models will be developed utilising Infra-red spectroscopy and evaluated to estimate key soil attributes for measuring PMN cost-effectively and rapidly.
Develop pedo-transfer functions to estimate PMN: Pedo-transfer functions will be developed to estimate PMN, which are equations that use easier to measure soil properties to predict those that are harder to determine. This will enable the rapid and cost-effective estimation of the PMN with measured or estimated inputs using IR technology.

Expected Outputs

Feasibility of using infra-red spectral measurement methods and predictive models and pedo-transfer functions for rapid and cost-effective estimation of soil organic carbon, labile and stable C fractions and PMN for soils in sugarcane growing regions.
Soil spectral libraries and associated predictive models and/or pedo-transfer functions for soil organic carbon, labile and stable C fractions and PMN representative of key sugarcane growing regions in Qld.
New insights into the release of key nutrients through the mineralisation process of soil organic matter.
Industry workshops for sugarcane growers and extension officers.
Research and Cane Matters publications and presentations at industry conferences and other events.

Expected Outcomes

Outcomes:

SRA laboratory services, field agronomists and extension officers utilise cost-effective methods to determine soil organic carbon, labile and stable C fractions and derive PMN.
Reduced cost and time to deliver critical soil information to growers enabling improved decision-making regarding fertiliser management and soil health assessments.
Enabling environment (via the provision of data and methods) for new agronomist soil services regarding N mineralisation and soil health assessments.
Enabling environment for assessing PMN and soil organic matter from a broad range of sugarcane growing environments and yield interactions via industry trials.

Impacts:
Cost-effective method developed to reduce soil testing costs.
Increased soil information, together with its timely delivery enables industry, growers, agronomists and policy to make agile decisions (long-term).
Development of a decision support tool for utilising the new methodologies and knowledge when making nutrient management decisions.
Enhanced data-driven decision-making for sugarcane farming system management practices.
Pathway towards a sustainable sugarcane farming system in Qld and the broader Australian industry through improved soil carbon and nitrogen diagnostic methods.