Annual bluegrass (Poa annua L.) was controlled in bermudagrass [Cynodon dactylon (L.) Pers.] turf when ethofumesate [(±)-2-ethoxy-2,3-dihydro-3,3-dimethyl-5-benzofuranyl methanesulfonate] was applied at 1.1 kg/ha in October and again in November, but not when applied in February and March. A single, October ethofumesate treatment, did not affect spring growth of nonoverseeded bermudagrass, but the growth of selected cultivars was delayed slightly from October + November treatment. Turf growth was severely delayed for all bermudagrass cultivars when ethofumesate treatments were delayed until February and March. The October and November ethofumesate treatments reduced the quality of overseeded perennial ryegrass [Lolium perenne (L.) ‘Medalist VI’] slightly, but did not injure it permanently and the turf recovered fully. The transition from ryegrass back to bermudagrass turf was good in the spring regardless of ethofumesate treatment. Even though turf cover was excellent throughout the transition period, bermudagrass cover during June and July was less when ethofumesate was applied in October than when application was delayed until after bermudagrass became dormant.

Experiments were conducted at three locations to evaluate the efficacy of fall and spring herbicide treatments for vegetation control and enhancement of alfalfa (Medicago sativa L.) establishment. on a sward dominated by quackgrass [Agropyron repens (L.) Beauv.], fall and spring glyphosate [N- (phosphonomethyl) glycine] treatments were equally effective in reducing competition from quackgrass and in establishing alfalfa. on a mixed grass sward, spring and fall glyphosate treatment resulted in similar alfalfa yields with early spring seeding; however, alfalfa yields were lower with delayed seeding on fall-treated plots, compared with spring treatment, because of greater weed competition. Pronamide [3,5-dichloro(N-1,1-dimethyl-2-propynyl) benzamide] applied in the fall controlled perennial grasses, and when it was followed by paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) in the spring controlled broadleaf weeds as well, resulting in greater alfalfa yields compared with pronamide alone. Alfalfa established more slowly in the paraquat-treated and check plots, than in glyphosate-treated plots.

Gibberellin-enhanced response of bean plants (Phaseolus vulgaris L. ‘Black Valentine’) and Canada thistle [Cirsium arvense (L.) Scop.] to bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] and glyphosate [N-(phosphonomethyl)glycine] was determined on both species under controlled photoperiods in the growth chamber and on Canada thistle under natural conditions in the field. Pretreatment of bean plants in the growth chamber with 10 mg/L gibberellin (GA3 or GA4/7) more than doubled the herbicidal effect of 1600 mg/L bentazon treatments. Pretreatment of Canada thistle plants in the growth chamber with 100 mg/L GA4/7 increased the herbicidal effect of 50 mg/L bentazon applications more than four-fold, and that of 400 mg/L glyphosate applications by more than two-fold. The phytotoxicity of bentazon to field-grown Canada thistle increased 10% or more in populations pretreated with 25 g/ha gibberellin; and that of 840 g/ha glyphosate was similarly increased. The effectiveness of a higher glyphosate dosage (1680 g/ha) was not significantly increased by GA pretreatment. Plants induced to bolt with gibberellin (GA4/7) were injured more by bentazon than were plants that bolted naturally.

A three-piece soil-sampling device was constructed to collect soil cores in polyvinyl chloride tubing to a depth of 92 cm with no or minimum contamination. The device with tube is driven into the soil with a hydraulic post-driver and removed with a chain attached to the bucket of a front-end loader on a tractor. Various depths can be sampled for analysis by cutting off proportionate sections of the tubing containing the soil core. This procedure is more rapid and poses less chance of contamination than by taking progressively deeper soil samples.

Solarization by means of transparent polyethylene sheets for 1 week in mid-summer significantly (P = 0.05) reduced numbers of viable prickly sida (Sida spinosa L.), common cocklebur (Xanthium pensylvanicum Wallr.), velvetleaf (Abutilon theophrasti Medic.) and spurred anoda [Anoda cristata (L.) Schlect.] seeds remaining after burial in soil. Solarization treatments for 1 to 4 weeks significantly reduced the total weed emergence of prickly sida, pigweeds (Amaranthus species), spurred anoda, morningglories (Ipomoea species), horse purslane (Trianthema portulacastrum L.), and various grass species from natural seed populations for the growing season by 64 to 98%. Purple nutsedge (Cyperus rotundus L.) emergence was increased by solarization in some instances. It was not determined if the increased emergence was from tubers or seeds. Maximum temperatures at the 1.3-cm soil depth under the polyethylene sheets reached 65 to 69C for 3 to 4 h of the mid-afternoon on clear days as compared with 43 to 50C at 1.3 cm in the soils that were not covered. Surface soil-moisture levels were also elevated under the polyethylene covers. Although solarization did not eliminate dormant weed seeds from the germination zone, the treatment killed nondormant seeds and greatly reduced the number of weed seedlings that otherwise would have emerged.

Twenty days after rice (Oryza sativa L. ‘IR28’) emergence, water was withheld from the stress treatment for 20 days while the control was kept well-watered by furrow irrigation. In the control plots, rice leaf water potential at 0800 hours was –5.5 bars and leaf length 30 cm on the 12th day of stress. In the stress treatment, leaf water potential decreased to –8 bars and leaf length to 20 cm, when no weeds competed with rice. With maximum weed competition, rice leaf water potential decreased to –18 bars and leaf length to 15.5 cm. on the 20th day of stress, dawn (0600 h) leaf water potential of rice in the stress treatment was reduced from –8 bars when no weeds competed with rice to –19 bars when competition was maximum. The weed species had higher water potential values than the rice in both control and water-stress treatments.

Herbicides were applied annually in March or March plus August to bermudagrass [Cynodon dactylon (L.) Pers. Tifdwarf’] putting greens for 6 yr. Bensulide [O,O-diisopropyl phosphorodithioate S-ester with N-(2-mercaptoethyl)benzenesulfonamide] delayed early spring growth of bermudagrass less than the other herbicides, but did not adversely affect turf quality during the growing season. Oxadiazon [2-tert-butyl-4(2,4-dichloro-5-isopropoxyphenyl)-Δ2-1,3,4-oxadiazolin-5-one] treatments applied twice each year severely retarded turf growth and reduced the quality and stand of bermudagrass. Napropamide [2-(α-naphthoxy)-N, N-diethylpropionamide] and prosulfalin {N-[[4-dipropylamino)-3,5-dinitrophenyl] sulfonyl]-S,S-dimethylsulfilimine} treatments reduced root growth of bermudagrass.

Nine soil-applied herbicides were evaluated in the field in cotton (Gossypium hirsutum L.) and soybeans [Glycine max (L.) Merr.] and in the greenhouse without crops to determine their effects on the control, regrowth, and tuber production of yellow nutsedge (Cyperus esculentus L.). Fluridone {1-methyl-3-phenyl-5-[3-(trifluoromethyl) phenyl]-4(1H)-pyridinone} and norflurazon [4-chloro-5-(methylamino)-2-(α,α,α-trifluoro-m-tolyl)-3(2H)-pyridazinone] provided the best (100%) control in the greenhouse. Tubers exposed to herbicide-treated soil in the greenhouse for 4 or 8 weeks produced fewer new tubers when transplanted into nontreated soil than nontreated tubers did. Yellow nutsedge shoot and tuber populations in the field were significantly reduced by all herbicides, except for alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide], after 2 yr of treatment in cotton and soybeans.

Field sudies on the persistence of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] showed less persistence under coulter than chisel or conventional plow tillage in the year of application. The residue on the coulter system from the previous corn (Zea mays L.) crop initially prevented as much as 30% of the atrazine from reaching the soil surface. After five annual applications, the atrazine residue was generally higher in the coulter than the chisel or conventional tillage systems, but below levels considered to be biologically active.