Nitrogen use in Tifway bermudagrass, as affected by trinexapac-ethyl

Nutrient movement from turfgrass systems into surface and ground water is a public concern. Data indicate that actively growing turf rapidly immobilizes applied N, thus restricting nutrient movement. It is possible, however, that growth suppression with plant growth regulators (PGRs) could reduce N demand and thus N uptake, resulting in greater leaching losses. An experiment was conducted with column lysimeters to investigate the effects of trinexapac-ethyl (TE) on nitrate leaching and N-use efficiency in Tifway bermudagrass (Cynodon dactylon x C. transvaalensis). The experiment was conducted in a growth chamber with day/night temperature set at 29/24 degreesC and a 12-h photoperiod. Trinexapac-ethyl was applied twice at 4-wk intervals at 0.11 kg a.i. ha(-1). Ammonium nitrate (AN) was applied at 50 kg N ha(-1) 2 wk after each TE application, and again 6 wk after the second TE application. Separate sets of columns received N-15-labeled AN for the first two applications. Irrigation was scheduled to provide a leaching fraction of approximate to50%; leachate was collected after each irrigation and analyzed for nitrate and ammonium. Cumulative nitrate leaching was unaffected by TE after the first two N applications, but was reduced approximate to60% by TE following the third N application. Trinexapac-ethyl reduced N-15 allocation to clippings by approximate to25% and increased N-15 allocation to roots and rhizomes; total recovery of applied N-15 in tissues was approximate to65%. Results demonstrate chemical growth suppression with TE does not reduce N uptake or increase nitrate leaching from bermudagrass.