Moisture Sensor‐Controlled Irrigation for Reducing N Leaching in Bermudagrass Turf¹

The study was conducted to determine the feasibility of using a tensiometer‐controlled irrigation system to reduce N leaching in turfgrass while maintaining acceptable growth. Bermudagrass ( Cynodon dactylon × C. transvaalensis ) was grown on a sand soil (Pomano fine sand, a siliceous, hyperthermic Typic Psammaquent) during a series of 2‐month (bimonthly) cycles. Irrigation was applied either daily (Daily irrigation), or when permitted by tensiometer soil moisture sensors (Sensor irrigation). Nitrogen at the rate of 5 g m −2 month −1 was applied bimonthly as NH 4 NO 3 , (AN) or sulfur‐coated urea (SCU), or as NH 4 NO 3 , through the irrigation system with each irrigation (Fertigation). The effect of these treatments on turfgrass color, clipping weights, and on tissue N content were measured. Nitrogen was determined in soil water samples obtained on a near daily basis from below the rootzone using ceramic cup suction lysimeters. Nitrogen leaching ranged from 56% to less than 1% of that applied, depending on treatment and cycle. The AN source combined with Daily irrigation produced the greatest N losses (22 to 56%), and Fertigation with Sensor irrigation produced the smallest losses ( <l to 6). Sensor irrigation reduced N leaching from all N sources. For SCU and Fertigation with Sensor irrigation, the peak and average N concentrations were less than 0.9 and 0.3 mmol L −1 , respectively, whereas for AN these values were as high as 2.8 and 1.0, respectively. The combination of Sensor irrigation and fertilization by Fertigation or SCU produced the least N leaching while maintaining acceptable turfgrass growth and quality.