B.FLT.5005 - Organic amendment calculator

Summary

The integration of plant nutrients released from organic soil amendments into farm fertiliser budgets allows not only for the reduction of synthetic fertiliser rates without compromising crop yield, but also multiple environmental and soil health co-benefits. This project provided farmers, agronomists and suppliers of manures and composts with a decision support tool for integrating organic amendments into farm nutrient budgets. On-farm field validation and demonstration sites from the Queensland to Victoria across vegetables, cotton, cropping and pasture showcased the tool and provide case studies of reduced fertiliser use and cost reductions, yield benefits possible from using organic amendments, and potential additional soil health and sustainability benefits. The manure and compost nutrient calculator is freely available as a farmer-friendly web and smart phone application.

Objectives

The aim of this project is to provide farmers, agronomists and suppliers of manures and composts with a decision support tool for integrating organic amendments into farm nutrient budgets.

Key findings

Overall the project tested 65 different organic amendment types across 20 different field trials over four years. Sites were located from Roma in Queensland, through to Geelong in Victoria, spanning the beef, dairy, irrigated and dryland cropping and intensive horticultural industries. A common methodology was used across the sites, a combining laboratory analysis and farmer field trial and demonstration sites. The Organic Amendment Nutrient calculator was developed using the data generated from the lab and field analysis, and incorporated farmer feedback from the workshops.

Benefits to industry

The calculator is free to use as a web or phone based application, and provides farmers with a one-stop resource for using organic amendments. It allows farmers to easily tap into the OA nutrient database generated by the project to predict how the supply of nutrients from the OA will meet the plant requirements from a range of key Australian crops, and compare the prices with conventional fertiliser. The calculator can be found here: https://oa-nutrient-calculator.netlify.app/.

As well as developing the calculator the project engaged with OA generators such as feedlots, composters, agronomists, state government regulatory bodies and of course farmers to demonstrate the advantages and challenges of incorporating OA’s into farm nutrient budgets. Over the four years the project conducted 14 farmer/industry workshops, 12 conference seminar or webinars, 10 newsletter or media releases, 8 on-farm field tours and 7 scientific papers or conference proceedings.

MLA action

MLA will continue to explore ways that the Australian feedlot industry can increase value of manure and effluent produced by the sector.

Future research

The variability of OA products remains the key barrier to their wider incorporation into farm nutrient budgets. Even using best practice of nutrient testing, there is a mismatch between how they are sold, transported and applied (per meter cube fresh weight), and how their nutrient contents are reported (kg per dry weight). As such moisture content and bulk density are the two largest variants of what ends up on the farmer field – and neither are reported well.

Several questions remain, all of which point towards the need for long term trials. This project covered some of the driest, and wettest years in Australian history, but even then it didn’t cover the range of crop rotations, management and climatic conditions experienced on the average farm. Permanent, long-term trials are required to better understand the interaction OA nitrogen and synthetic urea nitrogen has on nitrogen mineralisation throughout the season, and can this be used to further reduce N rates without compromising yield or quality.