RiskWi$e Project – Theme 2 Managing Phosphorus in the Farming System (Enterprise Agronomic Decisions)

Collaborating with CWFS, FarmLink and CSU, this project is funded by GRDC.

Theme 2: Phosphorus savings in Farming Systems – what risk?

The Participatory Action Research (PAR) process identified phosphorus (P) management as a priority amongst the grower and advisor community. With nitrogen work underway, P is the next largest, unavoidable expense for growers. In the target area (wider Griffith region) many of the soils have Colwell P values >40 mg P/kg soil.

Budget forecasting for the coming season projected very low returns, driven by softening commodity prices (particularly wheat) and high input costs. Growers are looking carefully as reducing the cost of production and by reducing P inputs, where soils have Colwell P values > 40 mg P/kg soil, as a measure of reducing cost of production risk. They are concerned about the unknown effects of reducing P inputs on a short-term bases on subsequent production and profit.

As growers have gradually accumulated P in their soils to above the critical range, they want to know where budget forecasts show low or negative profit outcomes, can they reduce P inputs without impacting profits in the year of implementation and in subsequent years.

As a result, Ag Grow Agronomy will test P saving decisions to inform risk/reward and profit by testing P application methodologies to establish:

• if short term input cost savings can be achieved with little or no risk to profit outcomes and
• if more flexible P input arrangements produce similar results to the set input arrangements.

This includes establishing an experiment in 2024 that sets up initial starting Cowell P values (~40 ~60 and ~90) that will allow us to test P saving strategies in following years.