Fertiliser Association Practice Guidelines Based on Science

The Fertiliser Association of New Zealand published a revised and updated Code of Practice for fertiliser management in March 2023, drawing on science produced by Our Land and Water.

The Code of Practice is a key resource tool for the management of fertiliser on arable and pastoral farms, horticulture and viticulture blocks, and market gardens, to avoid or minimise the loss of nutrients to the environment. Improving nutrient management is an important mitigation activity that can support improvements in freshwater quality, a critical aspect of Our Land and Water’s core objective.

The Code provides guidance for farmers, growers and farm advisors to use when developing nutrient budgets, nutrient management plans, farm plans and freshwater farm plans. It is also relevant for regional council planning and technical staff.

The revised Code (replacing the previous version published in 2013) had extensive input from agricultural and scientific experts, including Our Land and Water’s chief scientist Prof Richard McDowell, who has led our research into Phosphorus Best Practice. Research from four Our Land and Water-funded journal articles, cited in the Code’s references, was used in four sections of the Code that provide guidance on practices to address risk:

1. Risk: Phosphorus exceeding plant or pasture requirements
2. Risk: Unacceptable environmental impacts from direct application
3. Risk: Fertiliser nutrient loss from susceptible production areas
4. Risk: Fertiliser nutrient loss by not matching timing with crop growth stage, weather conditions and soil temperature

In those sections, Our Land and Water science provided the definition of soil test target ranges, areas of accumulation, avoiding soils with low ASC (P retention) and critical source areas.

Phosphorus Best Practice research investigated whether practice and policy for fertiliser and farm dairy effluent (FDE) application were sufficient to minimise phosphorus loss.  The research also explored the factors affecting phosphorus loss after the application of fertilisers.

One key finding of this research was that when fertiliser is managed badly, it’s responsible for 30 to 80% of the phosphorus that drains away from a farm. When it’s managed well, that can decrease to less than 10%. This research also provided a scientific basis for New Zealand and Australian farmers to follow the fertiliser industry-developed ‘4R guidelines’:  apply fertiliser in the Right place, at the Right time, at the Right rate, and in the Right form.

Key collaborators in the Our Land and Water research were AgResearch, Lincoln University, the South Island Dairy Development Centre and Ballance Agri-Nutrients who supplied time and resources including study sites and fertilisers.

Our Land and Water’s chief scientist is a frequently published expert on phosphorus in freshwater, with his own wide network of established phosphorus researchers working in an agricultural context and a strong connection into the fertiliser industry. This meant that Our Land and Water was very well positioned to identify new and effective ways to reduce the impact of fertiliser-derived phosphorus in our waterways, to communicate these to the industry, and to provide an overview of the new Code of Practice.

This article was originally submitted to MBIE as an impact case study as part of Our Land and Water's 2022–23 annual reporting.

More information:

• Phosphorus Best Practice research
• Code of Practice for fertiliser management
• Farmer Factsheet: Science-based advice for applying phosphorus fertiliser
• Direct exports of phosphorus from fertilizers applied to grazed pastures in Australasia
• Why are median phosphorus concentrations improving in New Zealand streams and rivers?