Irrigation Management Effects On Nitrate Leaching.

Increased urbanization across the United States has caused increases in home lawn irrigation system installment as well as the amount of over-irrigation caused by these systems.  This is cause for concern about the leaching of nitrates from fertilizers in these urban watersheds.  The objectives of this research were to evaluate differences in nitrate leaching and water usage between soil moisture sensor (SMS) based systems and a standard homeowner irrigation controller setup.  The study was initiated at the Rocky Ford Turfgrass Research Center on a Chase silty clay loam in Manhattan, Kansas in 2011.  Plots of tall fescue [Festuca arundinacea] turfgrass were assigned to either a standard irrigation or SMS-based irrigation treatment.  Standard irrigation cycles ran three times weekly to apply 2.54 cm.  The SMS irrigation cycles ran when the predetermined stress threshold level, based on volumetric water content (21-25%), was reached for each zone sensor.  When an irrigation cycle occurred on a SMS-based zone, it applied 2.54 cm of water.  Subplots consisted of no fertilizer application and urea (46-0-0) and polymer coated urea (41-0-0), each at 122 and 244 kg N ha^-1 yr^-1.  A suction lysimeter was used to extract nitrate leachate monthly.  Turfgrass quality was at or above acceptable levels for all treatments throughout the study.  The SMS-based irrigation systems showed a water savings compared to standard irrigation practices during the study years from 2011-2013.  All leaching rates recorded throughout the study were below EPA acceptable levels of 10 mg L^-1.  Results indicated SMS-based irrigation systems conserved water compared to standard irrigation practices while providing acceptable quality.