Five year-round forage systems in a dairy effluent sprayfield: phosphorus removal

Area of Science:

• Agricultural Science
• Soil Science
• Environmental Science

Background:

• Dairy operations generate effluent rich in phosphorus (P).
• Forage crops are utilized in sprayfields to manage and recover excess P from dairy effluent.
• Sustainable nutrient management is crucial for reducing environmental impact.

Purpose of the Study:

• To evaluate five year-round forage systems for their capacity to remove phosphorus (P) from a dairy sprayfield in northern Florida.
• To determine the effectiveness of different forage combinations in P recovery over five annual cycles.
• To identify the most efficient forage system for P removal in this specific environment.

Main Methods:

• Five forage systems were tested: bermudagrass-rye (BR), perennial peanut-rye (PR), corn-forage sorghum-rye (CSR), corn-bermudagrass-rye (CBR), and corn-perennial peanut-rye (CPR).
• Forages were grown over five 12-month cycles with effluent P application rates of 80, 120, and 165 kg ha⁻¹ cycle⁻¹.
• Phosphorus removal was quantified for each system across the five cycles.

Main Results:

• The bermudagrass-rye (BR) system achieved the highest overall 5-cycle P removal (67 kg ha⁻¹ cycle⁻¹).
• Perennial peanut-rye (PR) system's P removal increased over time as the perennial peanut established and yielded more.
• Corn-based systems (CBR, CSR) showed consistent high yields but moderate P concentrations, while sorghum had low P levels.

Conclusions:

• The bermudagrass-rye system demonstrated the greatest potential for phosphorus recovery in northern Florida dairy sprayfields.
• System performance varied across cycles due to shifts in perennial forage establishment and yield.
• A high-yielding, persistent bermudagrass is likely the optimal warm-season forage for maximizing P recovery in these conditions.