Nitrogen increases evapotranspiration and growth of a warm-season turfgrass

The effect of N fertilizer rate on Kikuyu turfgrass [Pennisetum clandestinum (Hochst. ex Chiov)] evapotranspiration was evaluated during two summers. Evapotranspiration was measured using weighing lysimeters (205 mm in diameter by 625 mm in length) inserted in turfgrass field plots (10 m2). The experiment was a randomized plot design with three replicates. Treatments included two turfgrass ages (established from 20 wk or 20-yr-old turfgrass) and three N application rates (0, 50, or 150 kg N ha−1 yr−1). Evapotranspiration ranged from 2.8 to 7.5 mm d−1 (or 56–81% of evaporative demand), and varied with daily evaporative demand, turfgrass age, and N fertilizer rate. The older turfgrass used more water than the younger turfgrass during both summers; while increasing the N application rate also increased evapotranspiration for both turfgrass types (younger turfgrass only in the second summer). Evapotranspiration was positively correlated with turfgrass growth (r 2 = 0.74–0.80) and transpiring leaf area (r 2 = 0.78). Older turfgrass at all N treatments, and the younger turfgrass receiving 150 kg N ha−1 yr−1, had adequate growth, color, and leaf N concentrations. Optimizing fertilizer applications such that the minimum N required to maintain turfgrass quality is applied, is an approach for decreasing water consumption by turfgrass.