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- Author or Editor: Dennis P. Shepard x
A creeping bentgrass (Agrostis palustris Huds. `Penncross') green was treated with flowable tri-calcium arsenate (Ca-Ars) in increment levels of 17 or 34 kg·ha-1 in 12 multiple treatment date programs. Treatments were made over 4 years to determine effectiveness of initial applications and accumulated residues in controlling annual bluegrass (Poa annua var. annua L.) and large crabgrass (Digitaria sanguinalis L. Scop.) and to evaluate the phytotoxicity to the bentgrass. Multiple treatments of Ca-Ars at increments of 17 or 34 kg·ha-1 effectively controlled annual bluegrass and large crabgrass when cumulative application amounts totaled at least 136 kg·ha-1. Excellent control of annual bluegrass was achieved by timing treatments and soil residue buildup totals to coincide with the major germination and regrowth period of late winter to early spring. Optimum timing included treatments during the fall and spring. This treatment sequence also gave excellent control of crabgrass. Sustained control of both weeds was achieved when continued low level follow-up applications totaled >136 kg·ha-1. Penncross bentgrass appeared tolerant of Ca-Ars treatments totaling as high as 272 kg·ha-1. Arsenic apparently influenced thatch accumulation by killing earthworms.
A simplified design for measuring the height of turfgrass (or forage) was developed and used by the Louisiana Agricultural Experiment Station (LAES). The device is similar to the common “disc meter” devices used for turfgrass and forage height measurement, but it uses a constant-force spring to simplify construction and operation. Use-of a constant-force spring allows a steady operating force on the sliding member of the device and eliminates the need for machining slots, thus greatly simplifying construction and reducing cost. The simplified device has worked well in the turfgrass research program of the LAES.
Priming or presoaking seed of common carpetgrass (Axonopus affinis Chase) and centipedegrass [Eremochloa ophiuroides Munro. (Kunz)] increased germination percentage and decreased mean time of germination (MTG) at 20, 25, and 30 °C. The effect of presoaking and priming was dependent on grass species and temperature. The optimum seed germination temperature for both of these warm-season species was 30 °C. Maximum effect on common carpetgrass or centipedegrass seeds was achieved by priming in 2% KNO3; higher concentrations did not improve germination percentage or MTG, and 4% was in some cases detrimental. Germination was higher and MTG lower at 20 and 30 °C than at 15 °C. Presoaking common carpetgrass and centipedegrass seeds was the most efficient seed enhancement treatment for germination at 30 °C.
Common carpetgrass (Axonopus affinis Chase), mowed at 3.8 or 7.6 cm and fertilized with at least 98 kg·ha–1 N, maintained acceptable lawngrass quality during the 1993 and 1994 growing seasons. Cumulative vegetative growth (CVG) quality and coverage were increased in mowed plots fertilized with 98, 147, or 196 kg·ha–1 N. Unsightly seedheads were a problem in nonmowed plots 3 weeks after the start of the experiment, but did not appear in the mowed plots. Our results indicate that mowing common carpetgrass at 3.8 or 7.6 cm and fertilizing with 98, 147, or 196 kg·ha–1 N will provide acceptable turfgrass quality.
Field studies were performed on established carpetgrass (Axonopus affinis Chase) in 1994 and 1995 to evaluate plant growth regulators (PGRs) and application rates. Trinexapac-ethyl (0.48 kg·ha-1) improved turf quality and reduced cumulative vegetative growth (CVG) of unmowed and mowed plots by 38% and 46%, respectively, in 1995, and suppressed seedhead height in unmowed turf by >31% 6 weeks after treatment (WAT) both years. Mefluidide (0.14 and 0.28 kg·ha-1) had little effect on carpetgrass. Sulfometuron resulted in unacceptable phytotoxicity (>20%) 2 WAT in 1994 and 18% phytotoxicity in 1995. In 1995, sulfometuron reduced mowed carpetgrass CVG 21%, seedhead number 47%, seedhead height 36%, clipping yield 24%, and reduced the number of mowings required. It also improved unmowed carpetgrass quality at 6 WAT. Sethoxydim (0.11 kg·ha-1) suppressed seedhead formation by 60% and seedhead height by 20%, and caused moderate phytotoxicity (13%) in 1995. Sethoxydim (0.22 kg·ha-1) was unacceptably phytotoxic (38%) in 1994, but only slightly phytotoxic (7%) in 1995, reduced clipping yields (>24%), and increased quality of mowed carpetgrass both years. Fluazasulfuron (0.027 and 0.054 kg·ha-1) phytotoxicity ratings were unacceptable at 2 WAT in 1994, but not in 1995. Fluazasulfuron (0.054 kg·ha-1) reduced seedhead height by 23% to 26% in both years. Early seedhead formation was suppressed >70% when applied 2 WAT in 1994, and 43% when applied 6 WAT in 1995. The effects of the chemicals varied with mowing treatment and evaluation year. Chemical names used: 4-(cyclopropyl-x-hydroxy-methylene)-3,5 dioxo-cyclohexane-carboxylic acid ethyl ester (trinexapac-ethyl); N-2,4-dimethyl-5-[[(trifluoro-methyl)sulfonyl]amino]phenyl]acetamide] (mefluidide); [methyl 2-[[[[(4,6-dimethyl-2-pyrimidinyl) amino]carbonyl] amino] sulfonyl]benzoate)] (sulfometuron); (2-[1-(ethoxyimino)butyl-5-[(2-ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one) (sethoxydim); 1-(4,6-dimethoxypyrimidin-2yl)-3-[(3-trifluoromethyl-pyridin 2-yl) sulphonyl] urea (fluazasulfuron).