Phosphorus (P) applications to turfgrasses vary with the development stage of the plant. At establishment, it is common to use “starter fertilizers,” such as 12N–25P–10K, that are high in P and relatively low in nitrogen (N). Mature grass plants, however, are very efficient users of P. As the root system develops, the amount of P added as fertilizer decreases, unless the soil is very deficient in P. A common analysis for mature turf would be a 20N–2P–15K. The reason for this change is the relative immobility of P in the soil. At the time of establishment, the limited root system is unable to obtain sufficient P to meet the plant's needs for this element. The P does not readily move in the soil solution to the vicinity of the plant and it must be placed on the surface in close proximity to the developing root. At maturity, the fibrous, multibranched root systems of grasses make them some of the most efficient species at removing P from the soil. A major concern over the use of P fertilizers on turf in recent years has been the possibility of movement of this element into surface waters. Excess P in surface water may result in algal blooms and other environmental problems. While there is some reason for concern where fertilizers are applied on sidewalks and streets in urban areas, P movement from most turf areas is very limited and properly applied fertilizer results in little damage to the environment.
Three preemergence herbicides [S-(0, 0-Diisopropyl phosphorodithioate) ester of N-(2-mercaptoethyl) benzenesulfonamide (bensulide) at 8.4 and 15.7 kg/ha, Dimethyl tetrachloroterephthalate (DCPA) at 11.8 and 16.8 kg/ha, and 2-tert-butyl-4-(2,4 dichloro-5-isopropoxyphenyl)-Δ2l,3,4-oxadiazolin-5-one (oxadiazon) at 2.2, 4.5, and 9 kg/ha] were applied to plugs of Kentucky bluegrass (Poa pratensis L. cvs. Baron, Enmundi, Newport, and Park) in the greenhouse. Bensulide and oxadiazon reduced root weight, but there were no cultivar differences. Cultivar differences in response to oxadiazon were observed for rhizome weight, rhizome length, and turfgrass quality, with ‘Newport’ and ‘Baron’ damaged more by oxadiazon than ‘Park’ and ‘Enmundi’. There were no cultivar differences in rhizome weight, rhizome length, and quality in response to bensulide or DCPA.
The practice of applying fertilizer in liquid form to turfgrass has become popular in the commercial lawn care industry, but foliar bum may become a problem following such applications. Fertilizer bum, ranging from leaf tip browning to bleaching of the entire leaf blade may result when a plant suffers physiological drought caused by an excess of soluble salts, either on the foliage or in the soil solution (2, 9). Researchers have reported that increasing levels of soil moisture stress may cause more severe fertilizer burn than nonstress conditions (4, 5, 6).
Chlorsulfuron was applied to annual bluegrass (Poa annua L.), creeping bentgrass (Agrostis palustris Huds ‘Penncross’), hard fescue (Festuca ovina var. duriuscula Koch ‘Scladis’), tall fescue (Festuca arundinacea Schreb ‘Kentucky 31’), quackgrass (Agropyron repens L. Beauv), smooth bromegrass (Bromus inermis Leyss), and perennial ryegrass (Lolium perenne L. ‘Crown’) at the rates of 0, 141, and 282 g a.i.·ha−1 in repeated greenhouse experiments. Tall fescue and perennial ryegrass were very sensitive to the chlorsulfuron in both experiments. Creeping bentgrass, hard fescue, quackgrass, and smooth bromegrass were more tolerant of chlorsulfuron treatments than the sensitive species. Annual bluegrass was damaged by chlorsulfuron in the first experiment, but not in the 2nd. Chemical name used: 2-chloro-N-[[(4-methoxy-6-methyl-l, 3, 5,-triazin-2-yl)amino]carbonyl]benzene sulfonamide (chlorsulfuron).
The objective of this study was to determine the effect of several preemergence herbicides and of fenoxaprop, a postemergence herbicide, on establishment of Kentucky bluegrass (Poa pratensis L.) sod. Fenoxaprop was applied at 0.20 and 0.40 kg·ha-1 28 and 14 days before sod harvest and 14 and 28 days after sod laying. Three preemergence herbicides, bensulide at 8.43 kg·ha-1, DCPA at 11.80 kg·ha-1, and pendimethalin at 1.69 kg·ha-1, were applied over the top of the freshly laid sod. All applications of fenoxaprop at 0.40 kg·ha-1 were phytotoxic by 14 days after application 8 weeks after sod laying in 1986. Fenoxaprop at 0.28 (1987 only) and 0.40 kg·ha-1 caused phytotoxicity on three of the four application dates, and fenoxaprop at 0.20 kg·ha-1 discolored the turf when applied 14 days before sod harvest. None of the treatments affected rooting 4 or 8 weeks after sod laying in 1987. Chemical names used: 0,(0-bis(1-methylethyl)-S-[2-[(phenylsulfonyl)amino]ethyl]phosphorodithioate (bensulide); dimethyl tetrachloroterephthalate (DCPA); (±)-2-[4-[(6-chloro-2-benzoxazolyl) oxy]phenoxy] propanoic acid (fenoxaprop); N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine (pendimethalin).
A series of studies was conducted during 2 years with various environmental and management conditions to investigate the effect of herbicides on rooting of Kentucky bluegrass (Poa pratensis L.). Benefin at 2.2 and 3.4 kg·ha−1, pendimethalin at 1.7 and 3.4 kg·ha−1, and DCPA at 11.8 and 16.8 kg·ha−1 inhibited rooting when tillers were grown in tubes in a greenhouse. Inhibition was greater in the upper 14 cm of the profile than deeper down. Prodiamine at 0.6 and 1.1 kg·ha−1 consistently reduced clipping weights and verdure. However, none of the treatments inhibited rooting in the field in the two years of the study. Chemical names used: N-butyl-N-ethyl-2,6-dinitro-4-(trifluoromethyl)benzenamine (benefin); dimethyl 2,3,5,6-tetrachIoro-1,4-benzenedicarboxylate (DCPA); (±)-2-[4-[(6-chloro-2-benzoxazolyl)oxy]-phen-oxy]propanoic acid (fenoxaprop); N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine (pendimethalin); N3,N3-di-n-propyl-2,4-dinitro-6-(triflouromethyl)-m-phenylenediamine (prodiamine).
The objectives of this study were to determine the effects of high P applications on `Baron', Kentucky bluegrass (Poa pratensis L.) turf quality, chlorophyll content, soil test levels of P and K, and foliar nutrient concentration. In this 5-year field study, P was applied at 0, 22, 43, 86, 172, or 258 kg·ha-1·year-1 using triple superphosphate (210 g P/kg) in single-applications in May. Phosphorus applications did not affect overall yearly quality, chlorophyll content, or soil pH, but increased available soil P and reduced available soil K and Cu concentration in clippings.