Nitrogen leaching and Tifway bermudagrass response to simultaneous nutrient and pre-emergence herbicide applications

Pre-emergence (PRE) herbicides are commonly applied simultaneously with fertilizers to turfgrass; however, the influence of PRE herbicides on nitrogen (N) uptake and leaching from turfgrass remains unclear. The hypothesis of this study was that PRE herbicides applied simultaneously with N fertilizers increase N leaching from Tifway 419 bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy, 'Tifway'] above that from fallow soil. A nutrient leaching study was conducted from June 2017 through June 2019 in Fort Lauderdale, FL. Treatments consisted of indaziflam (25 g a.i. ha^-1 ), prodiamine (540 g a.i. ha^-1 ), and oxadiazon (4,480 g a.i. ha^-1 ); a nontreated turfgrass control (turfgrass fertilized but not treated with PRE herbicides); and a fallow soil. Fertilizer (15-2-12) was applied every 60 d at 49 kg N ha^-1 , and PRE herbicides were applied every 120 d. Pre-emergence herbicides resulted in a 3.6- and 5.5-fold increases in NO₃ -N concentration compared with fallow soil during June 2017 and January 2018, respectively, whereas fallow soil resulted in increased NO₃ -N concentration during 10 mo and ranged from 3.8- to 15-fold greater than that from turfgrass plots. Turfgrass plots resulted in reduced N leaching of ∼7% during 5 mo compared with fallow soil and did not result in increased N leaching during any month. Cumulative N leached from turfgrass plots ranged from 75 to 120 kg ha^-1 and did not differ from fallow soil. Turfgrass growth rate and N uptake were not influenced by PRE herbicide. The results indicated that fertilizers applied with PRE herbicides does not result in increased N leaching or reduced N uptake.