The effects of nitrogen rate and frequency on Tifway 419 bermudagrass were studied, using a combination of sub-surface drip irrigation and fertigation with urea ammonium nitrate (UAN, 32-0-0) as the nitrogen source. Fertigation treatments were arranged into 3 frequencies (monthly, bi-monthly, weekly) X 5 nitrogen rates (0, 12.2, 24.4, 48.8, 97.7 kg N·ha⁻¹ ·month) with 4 replicates per treatment for a total of 60 lysimeters. Turfgrass quality and growth parameters were observed, as well as soil and leaching parameters.

Soil analysis was performed to determine the concentration of nitrate-nitrogen (mg·L⁻¹) at depths of 0 to 15 and 15 to 30 cm over a four week period. Rate was found to be significantly different at both soil depths during each of the four weeks. The 0, 12.2, and 24.4 kg N·ha ⁻¹·month⁻¹ rates had nitrate levels below 9.61 mg·L⁻¹ which prevented large amounts of leaching from occurring at these rates. The 48.8 and 97.7 kg N·ha ⁻¹ ·month⁻¹ rates had nitrate-nitrogen levels exceeding 30 mg·L⁻¹ which caused nitrate and nitrite leachate values to drastically exceed EPA limits after heavy rainfall events. The leachate analysis of nitrate and nitrite showed rate having a significant difference during the second and third samplings. In the third leachate sample, nitrate and nitrite levels exceeded EPA limits above the 12.2 and 24.4 kg N·ha⁻¹·month⁻¹ rates respectively.

Fertigation rate had a significant effect on turfgrass vigor through out the growing season. In the leaf tissue analysis, fertigation rates between 12.2 and 48.8 kg N·ha⁻¹·month⁻¹ were statistically the same with the 97.7 kg N·ha⁻¹ ·month⁻¹ rate being significantly higher. However, all rates except the control were within the sufficiency range of 3–5% nitrogen in the leaf tissue (McCarty, 2001). The control was below this sufficiency range and had signs of nitrogen deficiency which ranged from stunted growth to light green and yellow leaf blades. Visual quality rating of the turfgrass also showed a significant difference between all five rates throughout the growing season. Turfgrass quality rating peaked at the 24.4 to 48.8 kg N·ha⁻¹·month⁻¹ application rates and declined a little at the 97.7 kg N·ha ⁻¹·month⁻¹. The 97.7 kg N·ha ⁻¹·month⁻¹ rate started to show signs of toxic nitrogen levels including, burnt leaf blades and reduced cold weather tolerance.

Frequency did not play a significant role in this study. Results from the study indicate that a fertigation rate 12.2 kg N·ha⁻¹ ·month⁻¹ produced a quality turfgrass while minimizing nitrate and nitrite leaching levels below EPA standards when a using sandy-loam soil. Even though frequency did not play a significant role, it is recommended that a frequency of 7 to 14 days be used when sandy or sandy-loam soil is being used.