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Determination of crop coefficients (Kc), the ratio between actual (ETa) and reference evapotranspiration (ET0), is necessary to schedule irrigation. Our objective was to determine Kc, turf quality and growth rate under daily irrigation to field capacity (FC = −3 kPa tension) and drying. Minilysimeters installed in a green (mowing height 3–5 mm) and fairway (15 mm) were weighed during four periods of 4–10 days duration in 2009 and 2010. Crop coefficients on the second and subsequent days after irrigation were not significantly different among species and averaged 0.81 and 0.91 on green and fairway, respectively. On the first day after irrigation, the Kc varied from 1.67 to 2.85 and decreased in the order Agrostis capillaris > Festuca rubra ssp. litoralis > F. rubra ssp. commutata > A. stolonifera > A. canina on the green, and F. rubra ssp. litoralis > Lolium perenne > F.rubra ssp. rubra > Poa pratensis > F. rubra ssp. commutata on the fairway. Drying reduced the average daily height growth from 0.98 to 0.74 mm on the green and 1.97–1.72 mm on the fairway. Scores for turf quality were reduced but remained acceptable. Although the Kc during the first day after irrigation to FC may be overestimated due to latent soil heat and a possible oasis effect, we conclude that irrigation to FC should be avoided as it causes excessive water use.

Red fescue (RF, Festuca rubra L.) is used on golf putting greens in the Nordic region due to its high disease resistance and low requirements for nitrogen (N) and water, but low density and growth rate makes RF susceptible to annual bluegrass (AB, Poa annua L.) invasion. Putting greens seeded with RF + bentgrass (Agrostis sp.) may be more competitive with AB but also have different playing characteristics. Our objective was to compare RF, RF + colonial bentgrass (CB, Agrostis capillaris L.), and RF + velvet bentgrass (VB, Agrostis canina L.) putting greens at two mowing heights (4.0 or 5.5 mm), three N rates (5, 10, or 15 g N m−2 yr−1), and three phosphorus (P)–arbuscular mycorrhizal fungi treatments (0 and 1.8 g P m−2yr−1 without inoculation and 0 g P m−2yr−1 with inoculation). The four‐factorial experiment was conducted in 2011 and 2012 at Landvik, Norway. Red fescue provided lower visual quality and density and less competition against AB than RF + bentgrass combinations. Increasing the N rate from 5 to 15 g N m−2yr−1 increased the proportion of bentgrass tillers from 53 to 64% in RF + CB and from 86 to 92% in RF + VB. Surface hardness increased in the order RF + VB < RF + CB < RF turfs. Ball‐roll distance decreased with increasing N rate and was longer with RF and RF + VB than with RF + CB. The main effects of N and mowing height on AB invasion were not significant, but lower mowing increased AB competition in RF. Mycorrhiza colonization of roots was not significantly affected by any practice, and neither P nor arbuscular mycorrhizal fungi influenced the competition against AB.

Turfgrass grow‐in on sand‐based putting greens usually incurs a high risk for nitrogen (N) leakage. Our objective was to evaluate how substitution of a standard mineral fertilizer with an amino‐acid‐based fertilizer affects creeping bentgrass (Agrostis stolonifera L.) establishment rate and the concentration of nitrate and total N in drainage water. The experiment was conducted from 19 May to 26 July 2016 in the United States Golf Association green field lysimeter facility at Landvik, Norway. The liquid fertilizers arGrow Turf (70% of N as arginine and 30% as lysine) and Wallco (60% of N as nitrate and 40% as ammonium) were applied at ∼2‐wk intervals at the two rates of 1.5 or 3.0 g N m−2 application−1. Results showed significantly faster grow‐in on plots receiving amino‐acid‐based fertilizer than on plots receiving mineral fertilizers; the average turfgrass coverage 26 d after the first fertilization was 75 and 36%, respectively. In parallel with this, the average concentration of nitrate and total N in drainage water, as well as the total N loss, were all reduced by 40 to 45%. Arginine and lysine at 1.5 g N m−2 gave faster grow‐in than Wallco at 3.0 g N m−2 and was the only treatment in which the drainage water complied with EU's requirements for maximum concentration of nitrate in drinking water.

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