Year-round nitrogen fertilization effects on growth and quality of sports turf mixtures

The effect of three different nitrogen (N) levels applied monthly year-round on the growth and quality aspects of four different sports turf mixtures consisting of perennial ryegrass (Lolium perenne L.), tall fescue (Festuca arundinacea Schreb.), Kentucky bluegrass (Poa pratensis L.), creeping red fescue (Festuca rubra var. rubra L.), Chewings fescue (Festuca rubra var. commutata Gaud.), slender red fescue (Festuca rubra var. trichophlla), and Colonial bentgrass (Agrostis tenuis L.) were evaluated in this three year field irrigated study. Nitrogen was applied monthly at rates of low (2.5 g N m(-2)), medium (5.0 g N m(-2)), and high (7.5 g N m(-2)) starting in the first month after the sowing date in November 1998 and continuing for 34 months. The seasonal average differences in color, quality, cover percentages, and clipping yields of the mixtures were not significant. In contrast, N treatments greatly affected these characteristics, and differences were statistically significant at all the individual sampling dates and for seasonal averages during the three years of this study. Turf color and quality were generally associated with the N fertility treatments. Increasing N significantly (P < 0.01) enhanced the color and quality ratings and increased clipping yields in all turf mixtures. Fall and winter fertilizations significantly (P < 0.01) improved color and quality of turf without winter damage in the experimental area with mild winters. In particular, the high (7.5 g N m(-2)) rate resulted in decreased rooting at the both 0-15 cm and 15-30 cm depths