A cost-effective management practice to decrease phosphorus loss from dairy farms.

Area of Science:

• Agricultural Science
• Environmental Science
• Water Quality Management

Background:

• Phosphorus (P) loss from agricultural land is a significant contributor to surface water quality degradation.
• Dairy farm management practices, particularly pasture composition, influence nutrient runoff.
• Optimizing pasture management is crucial for mitigating environmental impacts and enhancing farm economics.

Purpose of the Study:

• To evaluate the impact of strategic grass-clover monoculture implementation on phosphorus loss in a grazed dairy farm.
• To compare the P loss and potential profitability of a split-management system (ryegrass near streams, clover elsewhere) versus a mixed pasture.
• To test the hypothesis that this strategic approach reduces P runoff and improves economic returns.

Main Methods:

• A paired-catchment study was conducted on a dairy farm over a defined period.
• The treatment catchment was divided: ryegrass (low P requirement) near streams, white clover (high P requirement) elsewhere.
• Fertilizer application rates for nitrogen (N) and phosphorus (P) were varied between monocultures and the control catchment.

Main Results:

• Filterable reactive P and total P concentrations in the treatment catchment decreased by 44% and 26%, respectively, after implementing monocultures.
• The shift to monocultures resulted in better-quality forage, indicating potential for improved farm profitability.
• A minor increase (2%) in modeled nitrogen loss was observed in the treatment catchment.

Conclusions:

• Strategic use of grass-clover monocultures in dairy farm catchments can effectively decrease phosphorus loss to surface waters.
• This management approach holds potential for enhancing farm profitability compared to conventional mixed pastures.
• While effective for P reduction, potential trade-offs like slight increases in N loss require careful consideration.