Swine effluent application timing and rate affect nitrogen use efficiency in common bermudagrass

Area of Science:

• Agronomy
• Soil Science
• Environmental Science

Background:

• Bermudagrass hay production is key for swine manure management in the Southeast.
• Synchronizing swine effluent application with crop nitrogen demands is vital to prevent soil nitrogen accumulation and nitrate leaching.

Purpose of the Study:

• To determine nitrogen-use efficiency (NUE) and residual soil nitrate-nitrogen (NO(3)-N) in bermudagrass under varying effluent application rates and timings.
• To assess the impact of swine effluent management on water quality.

Main Methods:

• Field studies on Prentiss sandy loam using two effluent rates (10 and 20 cm/yr) and four application timings (full season, early, mid, late).
• Harvesting forage every 7-9 weeks and sampling soil in fall and the following spring.
• Analyzing nitrogen and phosphorus uptake and residual soil NO(3)-N.

Main Results:

• Nitrogen and phosphorus uptake were lowest with August-September application timing.
• Doubling effluent rates significantly increased nitrogen uptake but also elevated soil NO(3)-N levels, especially in dry conditions.
• Low NUE (30-38%) was observed for late-season applications, indicating high risk for water contamination.

Conclusions:

• Swine effluent application timing significantly impacts nitrogen uptake and NUE in bermudagrass.
• Late-season applications pose a substantial risk to surface and groundwater quality due to increased residual soil nitrate.
• Optimizing effluent timing is essential for sustainable swine farming and environmental protection.