Crop response to nutrient application following mill by-product application to optimise nutrient inputs and manage impacts on CCS

Summary

Annually Australian sugar mills produce 1.5 million wet tonnes of mud and 200,000 wet tonnes of ash, as by-products of the milling process. They are generally used by farms within close proximity to the mill due to transport costs. Refining banded application at lower rates offers an opportunity to expand their availability to growers further from the mill due to improved profitability compared to the conventional practice.

Applying mill by-products at high rates can increase the risk of nutrient loss and negatively impact sugarcane CCS. While yield increases associated with mill by-product application have been demonstrated, there is limited research on optimising fertiliser decisions through the development of N response curves or the use of NIR technology to better inform nutrient management decisions following their application.

Objectives

Yield increases associated with mill by-product application have been demonstrated, however their negative impacts on CCS and profitability have also been observed. There has been limited research on optimising fertiliser decisions following the application of mill by-products.

The key objectives of this project are:
1. Refine the SIX EASY STEPS recommendations for modifications to nitrogen application rates where mill by-products are banded at rates less than 100 wet t/ha.
2. To maintain the yield benefit associated with mill by-product applications without suffering a CCS penalty.
3. Better understand the long-term impacts of mill by-products applied at rates less than 100 wet t/ha on CCS.
4. Improved understanding of the economic implications of utilising mill by-products at rates less than 100 wet t/ha.
5. Validation of NIR technology to assess moisture and nutrient content of mill by-products to better inform growers in real time of available nutrients provided by these products and their economic value.

The project aims to refine current guidelines (agronomic and economic) in the SIX EASY STEPS Toolbox for accounting for nutrients provided by mill by-products when applied at rates less than 100 wet tonnes/ha. It will also continue the development of NIR technology so that it can be utilised to provide real time analysis of nutrient and moisture content of mill by-products when exiting the mill or on delivery to the farm.

Expected Outputs

Output from this project will include:

1. Guidelines and publications
• Refinement of the Six Easy Step Toolbox. Agronomic and economic guidelines for using mill by-products will be updated.
• Development of a final report which will include agronomic, economic and NIR findings.
• Development of papers/s for presentation at ASSCT 2029 conference.
• Cane Matters article at project initiation (2024), mid project (2026) and project completion (2028).

2. Tools
• The continued development of NIR for assessment of mill by-product nutrient and moisture content at mills and in the field. Development of NIR devices which can be utilised by commercial providers or organisations such as productivity services.• Presentations at shed meeting, industry events, and field days providing project updates.
• Grower visits to trial sites in each region in collaboration with mill agronomists.

Expected Outcomes

Short term:
• An understanding of the agronomic and economic impacts of banding mill by-products and the opportunities for expansion of their use across industry.
• An understanding of the potential impacts of mill by-products on CCS.
• An understanding of the availability of macro and micronutrients in mill by-products for crop utilisation.
• The development of NIR calibrations for assessing nutrient availability in mill-by products.

Medium term:
• The adoption of mill by-products in areas where they were traditionally deemed too far from mills due to high transport cost.
• The commercial development of NIR devices which can be deployed and utilised by industry service providers to advise growers of nutrient status of mill-by products delivered on farm.
• NIR technology will provide opportunities for continued refinement of nutrient applications to maximise farm productivity and profitability.

SRA PROJECT CONTACT: Julian Connellan

RESEARCH AGENCY: Sugar Research Australia

CHIEF INVESTIGATOR: Julian Connellan with Co-investigator: Heidi du Clou, Sugar Research Australia and Co-investigator: Mark Poggio, Department of Primary Industries

PROJECT NUMBER: 2024/014

END DATE: 13/10/2028