Field Research & Agronomy

Nitrogen and Phosphorus on Pastures

Cost Based Decision Making

To assess the most efficient way to allocate nitrogen (N) and phosphorus (P) fertiliser spend on second year consecutive pasture rotation in the Cordering area.

For greater detail on this trial contact your Area Manager, or email our research team on research@summitfertz.com.au

‍Nitrogen and phosphorus fertilisers are utilised on pasture both to maintain soil levels and to improve productivity by allowing a higher stock carrying capacity.

Tactical nitrogen application can be used to generate feed to fill in season feed deficits. Continual cropping can deplete the soil of nutrients and organic matter resulting in altered nutrient requirements when entering back into a pasture phase.

This trial looks to determine the most profitable fertiliser spend on a ryegrass dominated pasture following a medium term cropping phase.

The trial will be continued over successive years to monitor compounding nutrient responses.

Being a grass based pasture, nitrogen responses were greater than phosphorus.

These results don't account for the decline in soil phosphorus levels if a farmer chooses to use only nitrogen.

The results reaffirm that in a pasture situation, higher rates over smaller areas are likely to have a greater overall impact than low rates over a larger area.
In practical situations using Phosphorus (and Potassium) with strategic HIGH rates of Nitrogen on parts of the farm is likely to give the best results.

Under these conditions for pasture grown the second year after a medium term cropping phase, 35 to 50 $/ha spent on nitrogen generated the highest dry matter and returns.

For the most profitable N application, a balance between application when the requirement for extra feed is greatest and when growth conditions are more favourable need to be weighed against each other.
Lower response efficiencies during winter when soils are cold and wet may be offset by the increased value of the feed generated.
The results reaffirm that in a pasture situation, higher rates over smaller areas are likely to have a greater overall impact than low rates over a larger area.