has been suggested to correspond with various anatomical and morphological plant characteristics. These char- Evaluations of Kentucky bluegrass (Poa pratensis L.) wear toler-acteristics include total cell wall content (TCW), quanance have been conducted; however, studies investigating wear mechanisms within this species is limited. This information would be valuable tity of schlerenchyma fibers, leaf width and leaf tensile in selecting wear tolerant genotypes. The objective of this study was strength, and shoot density (and verdure) (Shearman to identify anatomical and morphological characteristics in diverse and Beard, 1975band Beard, , 1975c. wear tolerant Kentucky bluegrasses. Wear treatments were applied Studies by Shearman and Beard (1975c) and Trento the 2000 National Turfgrass Evaluation Program (NTEP) Kentucky holm et al. (2000) have focused on the constituents of bluegrass field plots in the fall of 2002 at the University of Massachucell walls as a principle means of explaining turfgrass setts Joseph Troll Turf Research Center at South Deerfield, MA.wear tolerance. Cell wall components include cellulose, Wear treatments were applied to 173 genotypes with a differential hemicellulose, and lignin (Taiz and Zeiger, 1972). Celluslip-wear apparatus, and plots were visually rated for wear injury.lose is a tightly packed group of polysaccharide chains The 10 most wear tolerant (TOL) and intolerant (INTOL) genotypes that provides plant tissues with a high tensile strength. were selected for further evaluation. Twelve characteristics were measured in 2003 and 2004 comparing TOL and INTOL genotypes in This suggests that plants with higher percentages of field plots and as greenhouse grown spaced-plants. Characteristics cellulose may be more tolerant to wear stress. Hemiincluded tiller density, shoot fresh weight and dry weight, shoot water celluloses are a heterogeneous group of polysaccharides content, leaf turgidity, number of leaves per shoot, leaf width, leaf that bind to cellulose to further strengthen cell walls. strength, leaf angle, and leaf cell wall constituents [total cell wall Lignin is a highly branched polymer of phenylpropanoid content (TCW), hemicellulose, and lignocellulose]. Not all differences groups that possesses high mechanical rigidity and thereobserved in the greenhouse were present in field plots. Significant fore strengthens stems and vascular tissues (Taiz and differences were found between genotypes and TOL and INTOL Zeiger, 1972). Because of its physical toughness, lignin groupings. No significant interaction with year was detected. Tolerant deters feeding by animals (van Soest, 1994) and theregenotypes were associated with a more vertical leaf angle, greater fore may play a role in wear tolerance. TCW and lignocellulose content, and a lower shoot moisture content and leaf turgidity. Leaf angle was the single most important attribute Anatomical characteristics unique to the cell walls of separating wear TOL and INTOL genotypes. Biological explanation wear tolerant species have been ana...

A basic understanding of the eff ect of cultural practices on wear tolerance mechanisms in turfgrass is lacking. This information will be critical in helping turf managers optimize wear tolerance and thereby improve the quality and safety of sports fi elds. Nitrogen (N) and potassium (K) are the most frequently applied nutrients to sports fi elds, but little is known about the eff ects of N and K on wear tolerance and associated plant mechanisms. Several studies have been conducted on the eff ects of N and K on cool-season turfgrass wear tolerance, including Kentucky bluegrass (Poa pratensis L.) (Carroll and Petrovic, 1991) and creeping bentgrass (Agrostis palustrus Huds.) (Shearman and Beard, 1975a;Hawes and Decker, 1977;Carroll and Petrovic, 1991), but only Shearman and Beard (1975a) evaluated the eff ects of N and K on associated plant mechanisms. Shearman and Beard (1975a) reported that N increased wear tolerance and total cell wall content (TCW) content in creeping bentgrass, while K had no eff ect on TCW content but did increase wear tolerance. They also found that shoot density, verdure, leaf tensile strength, and moisture percentage increased with N. Potassium had no eff ect on measured parameters, although K fertilization was associated with decreased percentage moisture. In warm-season turfgrass, seashore paspalum (Paspalum vaginatum ABSTRACT Wear tolerance is important in sports turf, but the effects of nitrogen (N) and potassium (K) on wear mechanisms in perennial ryegrass (Lolium perenne L.) are unknown. The objective of this study was to evaluate wear mechanisms in response to N and K in this species. Field studies were conducted in 2006 and 2007 using fi ve N levels (49, 147, 245, 343, and 441 kg ha -1 yr -1 ) in combination with three rate levels of K (49, 245, and 441 kg ha -1 yr -1 ). Wear was applied in both years using wear simulators. Ten plant characteristics were measured in fi eld plots. Nitrogen had signifi cant effect on wear tolerance and plant characteristics. Shoot growth accounted for as much as 94% of the variation in wear tolerance (r = -0.97, P ≤ 0.001). Tissue moisture measured as relative water content and shoot water content covaried with shoot growth. Wear injury, shoot growth rate and tissue moisture increased with increasing N, especially when fertilized in excess of 245 kg N ha -1 yr -1 . Tissue moisture explained as much as 66% (r = -0.81, P ≤ 0.001) of the variation in wear tolerance. Cell wall components, leaf strength, and shoot density were secondary in explaining wear tolerance. Verdure was not important. Tissue K and soil-available K were not correlated with wear tolerance. These results suggest fertilizing at no more than 245 kg N ha -1 y -1 to maintain optimum wear tolerance, shoot growth rate and tissue moisture.

No abstract

RESEARCHP erennial ryegrass (Lolium perenne L.), along with Kentucky bluegrass (Poa pratensis L.), is cited as one of the most commonly used turfgrass species in athletic fi elds grown in cool-season climates (Puhalla et al., 1999). Turfgrass function and quality are aff ected by wear and soil compaction, the two major components of traffi c stress (Carrow and Petrovic, 1992). As the demand and use of sports fi elds increase, there is an increasing need for sports turf and fertility programs that maximize wear tolerance and recovery under intensely traffi cked conditions. Nitrogen and potassium are the most frequently applied nutrients to sports fi elds, but little is known about the interaction of N and K on wear tolerance and recovery from wear. Optimum N for maximum wear tolerance varies with the species. Nitrogen can promote an increase in wear tolerance up to some critical threshold beyond which wear tolerance can decrease. In perennial ryegrass, Canaway (1985) made comparisons between the eff ects of six rate levels of N ranging from 0 to 625 kg ha -1 yr -1 and found the optimum N level for maximum ground cover following wear to be 225 kg ha -1 yr -1 . Sorochan et al. (2001) detected little to no diff erence in wear tolerance of supina bluegrass (Poa supina Schrad.) and Kentucky bluegrass mixtures under two N rates (196 and 294 kg ha -1 yr -1 ). Carroll and Petrovic (1991) evaluated two rate

Applications of N are mandatory if acceptable yields are to be obtained from pure stands of reed canarygrass (Phalaris arundinacea L.). Potassium requirements and the N × K interaction are not well defined, however. A 3 × 3 factorial field experiment was conducted from 1983 to 1988 to evaluate the response of reed canarygrass to N and K fertilization. Rates of K were 0, 200, and 400 lb/acre and were applied annually. Nitrogen was applied at 0, 200, and 400 lb/acre in 1983 and 1984 and 100, 200, and 300 lb/acre from 1985 to 1988. Yields were consistently increased by N application. Initially, the response to K was minimal but in 1986 N × K interactions developed. Yield response to K was inconsistent when made in conjunction with 100 lb N/acre. At higher rates of N, however, positive curvilinear responses to K were obtained. Concentrations of K in the herbage reflected applied K levels. At the lowest N level, the application of K resulted in tissue concentrations of K that varied from 1.2 to 3.7%. These variations, however, were not associated with increased yields. When N was applied at 200 to 300 lb/acre, optimum yields occurred when herbage had K concentrations of 2.5 to 2.7%. Without K fertilization, soil test K values remained low (22 to 43 ppm). As K was applied, changes in soil test K varied with N level. The greatest increase in soil K occurred when low N fertilization was combined with high K fertilization, a change reflecting a major difference between applied K and K uptake. Where 200 or 300 lb N/acre was applied, recovery of K was approximately 100% when K was applied at 200 lb/acre. Maintaining soil test K between 40 and 60 ppm supplied sufficient K to support high yields of reed canarygrass fertilized with 100 to 300 lb N/acre.