Nitrogen Recovery, Use Efficiency, and Soil Losses of Three Cool-Season Turfgrass.
Kristina S. Walker and Cale Bigelow. Purdue University, 3164 Stratus Drive, 3164 Stratus Drive, West Lafayette, IN 47906
There is concern that nitrogen (N) losses from regularly fertilized turf is negatively affecting water quality. The purpose of this study therefore, is to not only assess soil N losses but to also assess above-ground plant responses to determine environmentally responsible N fertility programs for lawns. This two and one half year field study measured dry matter yield (DMY), leaf tissue N content, and potential soil N loss of eight N-programs which varied by N amount, 0 – 196 kg N ha-1 yr-1, and seasonal application timing of three cool-season lawn species: Kentucky bluegrass (Poa pratensis L.) (KBG), perennial ryegrass (Lolium perenne L.) (PRG), and turf-type tall fescue (Festuca arundinacea Schreb.) (TTTF). Dry matter yields for the study differed substantially between species and ranked, TTTF>KBG>PRG, with 9,426, 7,750, and 7,011 kg ha-1, respectively. Leaf tissue N ranked PRG>KBG>TTTF with 35.2, 33.9, 31.5 g kg -1, respectively. Nitrogen uptake (NUP), N recovery (NREC), and N use efficiency (NUE) was calculated, where TTTF (276 kg ha-1) had the greatest NUP followed by KBG (269 kg ha-1) and PRG (249 kg ha-1). Apparent NREC ranked, TTTF>PRG>KBG with 44, 41, and 39 %, of applied N. For NUE, values ranked 13.3, 11.1, 10.1 kg DMY kg N -1 for TTTF, PRG, and KBG respectively. Soil nitrate (NO3- -N) and ammonium (NH4+ -N) concentrations in soil solution as measured by suction cup lysimeters were low, < 1 mg L-1, throughout most of the study. Where N-loss is of concern a deep rooted efficient species like TTTF which is capable of producing high DMYs, NUP, NREC and NUE should be considered.