Nitrogen source and rate influence on tall fescue quality and nitrate leaching in a southern California lawn
In California, residential lawn area is second in planted acreage to production agriculture. Due to the demand for visually attractive lawns, relatively large amounts of N are often applied. The objective of this research was to investigate the effect of N source and application rate on tall fescue [Schedonorus phoenix (Scop.) Holub] visual quality and color, clipping yield, N uptake, and nitrate leaching under normal irrigation practices. Three annual N application rates (195, 293, and 390 kg ha–1) and four N sources (AN, ammonium nitrate; MUN, methylene urea; NON, natural-organic nitrogen; and PCN, polymer-coated nitrogen) were applied in four equal applications per year. The factorial experiment was replicated four times and conducted on a Hanford fine sandy loam at the University of California, Riverside's Turfgrass Research Facility from October 2002 to October 2004. Turfgrass visual quality and color ratings were evaluated every 2 wk. Clipping yield, clipping tissue total Kjeldahl nitrogen (TKN), and N uptake were measured or calculated in four 4-wk growth periods per year. Suction lysimeters were used to collect soil water below the rootzone (leachate) to determine nitrate and ammonium concentrations once every two weeks. Soil nitrate and ammonium concentrations were analyzed at 12 and 24 mo. after initial fertilizer treatments. An annual N application rate of 195 kg ha–1 produced an acceptable to good quality tall fescue lawn. Higher rates were not necessary, and increased nitrate leaching. Among the N sources, slow-release N resulted in less nitrate leaching than the fast-release N source.