Nitrogen Fertigation of Subsurface Drip Irrigated Bermudagrass.

Subsurface drip irrigated 'Tifway 419' hybrid bermudagrass (<i> Cynodon dactylon x C. transvaalensis</i>) was used to evaluate 5 fertigation rates (0, 12.2, 24.4, 48.8 and 97.7 kg N ha^-1 month^-1) using urea ammonium nitrate (32-0-0) and 3 frequencies (weekly, bi-monthly and monthly) factorial design with 4 replicates. Each experimental unit consisted of an above ground lysimeter with 5 cm of gravel at the bottom and 30 cm of sandy loam soil, sodded with hybrid bermudagrass, and a single 3.8 LPH drip emitter 15cm below the soil surface . Leaf tissue was collected once during the growing season to determine leaf nitrogen concentration. Leachate was collected after rainfall events that produced adequate sample and analyzed for nitrate-nitrogen concentration. Soil samples were collected weekly at depths of 0 to 15cm and 15 to 30cm during one fertigation cycle to determine soil nitrate-nitrogen concentrations. There was no significant difference in fertigation frequency for any of the parameters evaluated. Leaf tissue nitrogen was significantly lower at the 0 kg N ha^-1 month^-1 rate as compared to other rates. Except for the 0 kg N ha^-1 month^-1 rate all treatments were within the sufficiency range of 3 to 5% N. For soil nitrate levels rate was found to be significantly different at both soil depths during each of the four weeks (fertigation cycle). The 0, 12.2, 24.4 kg N ha^-1 month^-1 rates had nitrate levels below 9.61 mg L^-1l while the 48.8 and 97.7 kg N ha^-1 month^-1 rates had levels exceeding 30 mg L^-1. Leachate analysis of nitrate-nitrogen had a significant rate response with the 0 and 12.2 kg N ha^-1 month^-1 rates below EPA limits (10 mg L^-1). Results from this study indicate that a fertigation rate of 12.2 kg N ha^-1 month^-1 produced a quality turfgrass while minimizing nitrate leaching levels below EPA standards in a sandy loam soil.