Influence of overwatering and fertilization on nitrogen losses from home lawns

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Fertilized home lawns represent a potential source of NO3-N contamination to groundwater and surface waters. The waterborne losses of inorganic N from Kentucky bluegrass (Poa pratensis L.) turf subjected to three levels of N fertilization (0, 97, and 244 kg N ha-1 yr-1 as urea and methylene urea) and two irrigation regimes (scheduled by tensiometer and overwatering with 3.75 cm of water per week in addition to rainfall) were measured. The site was located on a Merrimac sandy loam (sandy, mixed, mesic Typic Dystrochrept). Soil-water percolate was collected by suction plate lysimeters placed below the root zone. Surface runoff was quantified with orifice flow splitters. Soilwater percolate flux comprised > 93% of the total water and inorganic-N discharged from all treatments. Mean annual flow weighted concentrations of inorganic N in soil-water percolate were below the U.S. drinking water standard on all treatments and ranged from 0.36 mg L-1 on the overwatered, unfertilized, control treatment to 4.02 mg L-1 on the overwatered, high N treatment. Annual losses ranged from 32 kg ha-1 on the overwatered high N rate treatment to 2 kg ha-1 on the scheduled irrigation, unfertilized, control treatment. Overwatering in conjunction with fertilization generated significantly higher annual flow weighted concentrations and mass loss than the unfertilized controls. Nitrogen loss and concentrations from the scheduled irrigation treatments were not significantly different from the controls.

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Journal of Environmental Quality