Environmentally Sustainable Nitrogen Fertilizer Management for ‘Tifton 85’ Hay Production in Sandy Soils

Nitrogen is a critical element for sustainable forage production but N surpluses in sandy soils could result in nitrate leaching and water contamination. Our objective was to identify a N application rate that optimizes yield and quality of ‘Tifton 85’ bermudagrass (Cynodon Rich. spp.) with minimal N leaching losses in a typical Florida sandy soil. Four N application rates (30, 50, 70, and 90 kg N ha−1 per harvest) and an unfertilized (0 N) control in a Tifton 85 bermudagrass hay field were evaluated. Suction lysimeters were installed in each plot at 30 and 100 cm below the soil surface to measure soil water nitrate concentration. Nitrogen application at the recommended rate of 90 kg N ha−1 per harvest produced the greatest total dry matter yield (DMY) (∼22 Mg ha−1 yr−1), but a modeled optimum DMY of ∼18 Mg ha−1 yr−1 occurred at 57 kg N ha−1 per harvest. Nitrogen application increased herbage nutritive value, but the difference was not significant above 30 kg N ha−1 per harvest. Treatments with N rates ≤ 50 kg N ha−1 per harvest had leachate nitrate concentration below the maximum contaminant limit (MCL) of 10 mg L−1. However, N rates ≥ 70 kg N ha−1 per harvest had leachate nitrate concentration that exceeded the MCL, suggesting a risk of impacting groundwater quality. The results demonstrate that although Tifton 85 bermudagrass is an efficient N remover, there is potential for N leaching in sandy soils. Therefore, site-specific evaluation of appropriate N management is critical.