Monday, 7 November 2005 - 9:45 AM
63-8

Nitrogen Fertilization Effects on Three Cool-Season Lawn Species in Indiana.

Kristina Walker and Cale A. Bigelow. Purdue University, 3164 Stratus Drive, West Lafayette, IN 47906

There is growing concern that excess nitrogen (N) is being applied to lawns and may be contaminating groundwater. The purpose of this two-year field study was to evaluate current lawn N recommendations and investigate alternative N programs for three cool-season lawn species grown in Indiana: Kentucky bluegrass, turf-type tall fescue, and perennial ryegrass. Eight N programs were designed ranging from 0 to 196 kg N ha-1 yr-1 applied as urea, sulfur coated urea or a combination depending upon season. Turfgrass N response was evaluated using dry matter yields (DMY), leaf tissue N content, and canopy greenness. Visual ratings for turfgrass quality and disease incidence and severity were also regularly recorded. Soil N was monitored using suction cup lysimeters, 45 cm below the soil surface, and by KCl extractions. As expected, DMY increased with N fertilization, especially for turf-type tall fescue. Additionally, leaf tissue N content increased with N rate, ranging from 2-5 %. Plots receiving multiple fall N applications retained their green color longer into the late-fall and generally had faster spring green-up except for Kentucky bluegrass. During July of both years, dollar spot severity was worst in perennial ryegrass, regardless of N program and Kentucky bluegrass receiving low, < 74 kg N ha-1 yr-1 N rates. Soil N levels were generally very low (< 1.5 ppm) except for under Kentucky bluegrass during spring green-up (April-May) where nitrate levels in some plots exceeded 10 ppm . For a moderate quality lawn, turf-type tall fescue or Kentucky bluegrass fertilized at 123 kg N ha-1 yr-1 applied in three annual applications is sufficient with minimal risk of N leaching.

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