Effect of leaf nitrogen concentration versus CND nutritional balance on shoot density and foliage colour of an established Kentucky bluegrass (Poa pratensis L.) turf

Abstract

N. 2006. Effects of leaf nitrogen concentration versus CND nutritional balance on shoot density and foliage colour of an established Kentucky bluegrass (Poa pratensis L.) turf. Can. J. Plant Sci. 86: 1107-1118. A 3-yr field study was conducted in a loam site and a sand site to determine the effects of N, P, and K application rates on N status, shoot density and foliage colour of Kentucky bluegrass clippings and to derive critical N values. The experiment was arranged in a completely randomized block design with four replicates and three nutrients, N (0 or 50 to 300 kg ha -1 yr -1 ), P (0 or 21.8 to 87.3 kg P ha -1 yr -1 ), and K (0 or 41.7 to 250 kg K ha -1 yr -1 ), equally broadcast six times per growing season. We examined N concentration values, log-transformed N concentration values, and CND values for compositional nutrient simplexes comprising one (V N1 ), three (V N3 ), five (V N5 ), or 11 (V N11 ) macro-and micro-nutrients. Critical values for N expressions were obtained from linear relationships with targeted visual shoot density and foliage colour ratings that were closely related to each other (R 2 = 0.92). The highest coefficients of determination (0.975 to 0.980) were obtained with V N5 and V N11 . The V N5 values were consistent with literature data and across experimental sites, and were the most successful (99% success) in diagnosing N sufficiency in 328 qualified specimens from commercial sod farms. Compared with raw concentrations, the CND transformation reduced from 0.6 to 0.1 the degree of inter-correlation among nutrients in principal component analysis and was amenable to a χ 2 distribution of CND indices. Using a critical imbalance index (CNDr 2 ) of 5.6 as χ 2 value, and a critical CND I N 2 index of 1.5 for a 5-nutrient simplex, we diagnosed as imbalanced 179 qualified specimens of which 110 specimens presented excessively high N level among the 328 qualified specimens in commercial stands. The proposed five-nutrient CND norms proved to be effective in diagnosing N status in Kentucky bluegrass clippings across experimental, literature, and survey data sets. To whom correspondence should be addressed (leon-etienne.parent@sga.ulaval.ca).

Defining Sufficiency Levels of Nitrogen in Cool‐Season Turfgrass Lawns Using Macy's Concept

“…This makes it difficult to make conclusive comparisons among studies that used different species and growing conditions. Our estimated sufficiency levels are within the few reported ranges for both the minimum and critical N concentrations (Bowman, 2003;Badra et al, 2006;Mangiafico and Guillard, 2007), but showed slight seasonal differences, as well as differences between the two cool-season turfgrass species.…”

“…A minimum concentration of N in the clippings, below which no net growth was predicted for this ryegrass species, was estimated to be 27 g kg -1 . Acceptable to optimum density and color of Kentucky bluegrass grown for sod in Quebec was obtained when clippings N concentrations ranged from 30.4 to ≥34.7 g kg -1 (Badra et al, 2006). In a field experiment in Connecticut with a mixed species cool-season lawn turf (Kentucky bluegrass, perennial ryegrass, and creeping red fescue [F. rubra subsp.…”

“…rubra]), linear-response plateau models predicted critical leaf tissue N concentrations from 30 to 34 g N kg -1 that maximized clippings yields and color (Mangiafico and Guillard, 2007), but no minimum concentrations were reported. Acceptable to optimum density and color of Kentucky bluegrass grown for sod in Quebec was obtained when clippings N concentrations ranged from 30.4 to ≥34.7 g kg -1 (Badra et al, 2006). In the same study, the CND approach was effective in diagnosing N status in Kentucky bluegrass clippings across experimental, literature, and survey data sets when the geometric mean used to compute row-centered log ratios was based on five nutrients (N, P, K, Ca, Mg).…”

Guiding fall fertilization of cool‐season turfgrass lawns with verdure tissue‐N tests

“…Dumort. ], 33 to 51 g kg -1 for perennial ryegrass, and 25 to 51 g kg -1 for Kentucky bluegrass (Mills & Jones, 1996), 27 to 35 g kg -1 for various species (Turner & Hummel, 1992), 30.4 to ≥ 34.7 g kg -1 for Kentucky bluegrass (Badra et al, 2006), 30 to 34 g N kg -1 for mixed species and separately for Kentucky bluegrass (Mangiafico & Guillard, 2007), and 32 to 46 g kg -1 and 28 to 42 g kg -1 for Kentucky bluegrass and tall fescue, respectively (Geng, Guillard, Mangiafico et al, 2014). These previous studies, however, report total N concentrations in the clippings and not the verdure.…”

“…Sufficiency or critical concentrations of total N in the clippings of various perennial cool‐season turfgrasses range from 24 to 82 g kg −1 , depending upon species and management systems (Badra et al., 2006; Butler & Hodges, 1967; Geng et al., 2014; Geng et al., 2014; Mangiafico & Guillard, 2007; Mills & Jones, 1996; Smith, Cornforth, & Henderson, 1985; Turner & Hummel, 1992). There are higher N concentrations in clippings than in the associated verdure (the aerial shoots and leaf blades remaining after mowing) (Kaufmann & Aldous, 1980; Picchioni & Quiroga‐Garza, 1999).…”