LAUSR

Funding information ScandinavianTurfgrass andEnvironment ResearchFoundation Abstract Phosphorus is an essential plant nutrient, but primary resources are limited and overfertilization may cause eutrophication of freshwater. Our objectives were to examine temperature effects on (a) optimal P rate for turfgrass establishment, and (b) increasing rates of foliar vs. granular P for early spring growth of established greens. Two trials, both on USGA root zones and replicated in April−May over 2 yr, were conducted in daylight phytotrons at 7, 12 and 17 C. Experiment 1 compared 5 P rates from 0 to 0.48 g P m−2 wk−1 for creeping bentgrass establishment on a sand containing 13mgPkg−1 (Mehlich-3). Results showedno temperature effect on the optimal P rate. Bentgrass coverage and clipping yield increased up to 0.12 and 0.24 g P m−2 wk−1, corresponding to 6 and 12% of the N input, respectively. The concentration of P in clippings was higher at 7 than at 17 C indicating that temperature was more limiting to shoot growth than to P uptake. A higher root/top ratio showed that plants invested more in roots under P deficiency. Experiment 2 was conducted using intact cores from a 4-yr-old creeping bentgrass (Agrostis stolonifera L.) green with aMehlich-3 P level of 34 mg P kg−1. Results showed increased clipping yields up to 0.18 g P m−2 wk−1 and higher P uptake with granular than with foliar application, but there was no effect on turfgrass color and no interaction with temperature. Low temperatures did not justify higher P applications.