N. 2005. Quantitative and qualitative responses of an established Kentucky bluegrass (Poa pratensis L.) turf to N, P, and K additions. Can. J. Plant . Kentucky bluegrass is a common turf species used on golf courses, sports fields, municipal parks, sod farms, road banks, as well as residential and school yards. Our objective was to determine the effects of N, P, K rates on turfgrass quantitative response (clipping yield and underground turf biomass) and qualitative response (shoot density and foliage colour) under a continuous clipping removal. A 3-yr field study was conducted on two sites, a sand that met the specifications of the United States Golf Association (USGA) and a loam. The factorial experiment was arranged in a randomized complete block design with four replicates and different levels of 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 ). The maximum clipping yield was produced at the rate of 200 kg N ha -1 yr -1 in the loam and 300 kg N ha -1 yr -1 in the sand. Increasing N rates linearly reduced underground turf biomass. Added P and K had no effect on clipping yield and underground turf biomass. Nitrogen significantly improved shoot density and foliage colour. However, equivalent shoot density and colour ratings required 40 to 80 kg more N ha -1 yr -1 in the sand compared to the loam. Phosphorus and K had no significant effect on shoot density and colour in the loam. Colour response to P and K depended on N rates in the sand. Fertilizer units needed to increase soil test P averaged 6 kg added P ha -1 mg -1 P M-III kg -1 across soil types. To replenish soil K, 7 kg K ha -1 per mg K M-III kg -1 were required in the sand, and 3 kg K ha -1 per mg K M-III kg -1 in the loam. Phosphorus and K fertilizer programmes should account for P and K removals to maintain low to medium fertility levels for P, and medium for K when conditions are similar to those in this research. [193][194][195][196][197][198][199][200][201][202][203][204]. Le pâturin des prés est une espèce de gazon couramment utilisée dans les terrains de golf, les terrains sportifs, les parcs municipaux, les gazonnières, les bordures de route, et les aires résidentielles et scolaires. Notre objectif était d'évaluer les effets de la fertilisation en N, P et K sur le rendement de débris de tonte, la biomasse souterraine du gazon, la densité de tallage et la couleur du feuillage en cas de débris de tonte ramassés. Une étude sur trois années a été réalisée sur deux sites, l'un sableux conforme aux spécifications de la United States Golf Association et l'autre loameux. Le dispositif expérimental était en blocs complets aléatoires avec quatre répétitions et différents niveaux pour trois éléments fertilisants, soit N (0 ou 50 à 300 kg ha -1 an -1 ), P (0 ou 21.8 à 87.3 kg P ha -1 an -1 ), et K (0 ou 41.7 à 250 kg K ha -1 an -1 ). Le plus grand rendement de débris de tonte a été produit par la dose de 200 kg N ha -1 an -1 dans le loam et 300 kg N ha -1 an -1 dans le s...

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).

rielce, utilisant les m€mcs g6notypes. datcs et densit6s dc semis, on a constat6 quc les rachis "tweaked" ct/ou branchds, observ6s sur les plants m0rs, ont comrncnc6 d €tre visible clurant lcs quelqucs premidres semaines du ddveloppemcnt de la plantulc. La formation dc ces anormalitds scmblait 6trc influenc6e par la temp6raturc ct la densit6 du sernls.For the past two decades, non-tillering Based on a uniculm barley breeding probarleys (Hordeum vulgore L.), usually gram, Donald (1978) observed that the uniknown as uniculms, have been observed to culm gene has many effects on the growth and develop morphological spike abnornialities development of the barley plant, namely: which aff-ect grain yield by decreasing the suppression of tillering, earlier maturity, and number of spikelets per spike. Uniculm increases in plant height, stem diameter, leaf barleys are the result of a mutation induced by length, leaf width and root growth. Kirby X-rays andthis non-tillering habit is control- (1973) For personal use only.

Kentucky bluegrass (Poa pratensis L.) is the most common perennial turfgrass species grown on playgrounds, municipal and residential lawn areas, and golf tees, fairways and roughs. Fertilization is the most efficient way to improve and maintain turfgrass aesthetic quality. Tissue diagnosis can guide fertilization, but tissue concentration ranges are biased by not taking into consideration nutrient inter-relationships, carryover effects and other key features. The centered log-ratio transformation reflects nutrient interactions in plants and avoids statistical biases. Machine learning (ML) models relate the target variable to the key features ex ante, and can predict future events from prior knowledge. The objective of his study was to predict turfgrass quality from key features and rank nutrients in the order of their limitations. The experimental setup comprised four N, three P, and four K rates applied on permanent plots during three consecutive years. Soils were a loam and an USGA sand. Eleven elements (N, S, P, K, Ca, Mg, B, Cu, Zn, Mn, Fe) were quantified in clippings collected during spring, summer and autumn every year. Turfgrass quality was categorized as target variable by color rating. Concentrations were centered log-ratioed (clr) partitioned into four quadrants in the confusion matrix generated by the xgboost ML model. The area under curve (AUC) and model accuracy were high to predict turfgrass color from the nutrient analyses of clippings collected in the preceding season, facilitating the seasonal adjustment of the fertilization regime to sustain high turfgrass quality. We provide a computational example to run the ML model and rank nutrients in the order of their limitations.