Arsenic residues in soil were examined annually over a 5-yr period following annual applications of MSMA (monosodium methanearsonate) at 4.4, 9, 13, 18, 22, 36, 72, 144, and 288 kg/ha. Elemental arsenic did not increase in any plot receiving MSMA rates less than 36 kg/ha. Plots receiving 72, 144, and 288 kg/ha of MSMA for 5 yr showed significant increases in arsenic residues. The arsenic residues for the two heaviest treatments (144 and 288 kg/ha) increased significantly during the first 4 yr, but did not increase in the fifth year.

Perfluidone (1,1,1-trifluoro-N-[2-methyl-4-(phenylsulfonyl)phenyl]-methanesulfonamide) was chemically stable for 2 to 3 weeks on the surface of three Texas soils either air dry or at field capacity and at temperatures of 22 and 46 C. Perfluidone was susceptible to photodecomposition when applied to glass petri dishes and exposed to ultraviolet irradiation. Perfluidone was readily leached through neutral or slightly alkaline soils, with a tendency toward greater downward movement in soils having low clay and organic matter content. However, leaching was less in an acid loamy sand than in either neutral loamy sand or clay soils.

Field and greenhouse experiments were conducted on bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)one 2,2-dioxide] at 2.2 and 4.4 kg/ha and perfluidone {1,1,1-trifluoro-N-[2-methyl-4-(phenylsulfonyl) phenyl] methanesulfonamide} at 4.5 and 9.0 kg/ha for purple nutsedge (Cyperus rotundus L.) control and tolerance of five turfgrasses. A single application of each herbicide was applied to purple nutsedge, but single and repeated applications were applied to turfgrasses. Purple nutsedge control during the initial year of treatment was 98 to 100% when bentazon was applied in late spring, but the control was only 28 to 68% when applied in mid or late summer. Perfluidone controlled 76 to 87% of purple nutsedge when applied in late spring and 95 to 100% when applied in late summer. Bentazon treatments generally did not cause turf injury. In the field, perfluidone treatments injured St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze], zoysia grass (Zoysia japonica × Z. teniuflolia ‘Emerald’), centipedegrass [Erenoehloa ophiuroides (Munro) Hack.], and common bermudagrass [Cynodon dactylon (L.) Pers.]. ‘Tifway’ bermudagrass was generally tolerant to perfluidone treatments. In the greenhouse, perfluidone reduced the root growth of all turfgrasses except centipedegrass when compared with untreated checks.

We investigated germination enhancement of downy brome (Bromus tectorum L.) seeds (caryopses) recovered from herbicide fallows in degraded big sagebrush (Artemisia tridentata Nutt.) communities. Numbers of germinable downy brome seeds were increased most by adding 0.1 mmole potassium nitrate (KNO3) or combinations of 0.1 mmole KNO3 and 0.14 mmole gibberellic acid (GA3). Germinability was enhanced in the fall and spring but not in midwinter when dormancy was greatest. Improved downy brome control and better establishment of seeded forage species with a fallow technique in sagebrush-dominated communities look promising if these growth regulators can be effectively applied in the field. Without germination enhancement, many germinable seeds of downy brome are present in litter under shrub canopies at the end of the fallow period. With near-optimal microenvironment under shrub canopies for plant growth, severe competition between downy brome and the seeded forage species can result.

We investigated seasonal variation in germinability of seed reserves in a degraded big sagebrush (Artemisia tridentata Nutt.) community. A bioassay was employed to determine germinability. There were many more germinable seeds and seedling establishment was greater under the shrub canopies than in the interspace. Caryopses of downy brome (Bromus tectorum L.) were the most abundant of any species in the litter where most of the seeds were located. Seasonal germinability of downy brome caryopses depends on the environment of the seedbed when the samples were collected and on the incidence of environmentally-induced dormancy or on loss of dormancy.

We studied the early root growth of four Setaria taxa: giant foxtail (Setaria faberi Herrm.), giant green foxtail [Setaria viridis var. major (Gaud.) Posp.], robust white foxtail (Setaria viridis var. robusta-alba Schreiber), robust purple foxtail (Setaria viridis var. robusta-purpurea Schreiber). Growth studies in controlled environments showed significant differences in root elongation among the taxa at three photoperiods. Seminal root lengths after 4 days followed the order presented for selectivity and metabolism of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] and propazine [2-chloro-4,6-bis(isopropylamino)-s-triazine] (robust white foxtail > giant green foxtail = robust purple foxtail > giant foxtail). Giant foxtail had the greatest root diameter, resulting in the greatest surface area and volume when lengths were equated. The order of seminal root lengths or diameters changed little after 7 days. Robust white foxtail had the most and longest first order lateral roots. Diameter of first order laterals showed giant foxtail > giant green foxtail = robust purple foxtail > robust white foxtail.

Peanut (Arachis hypogaea L. ‘Tifspan’ or ‘Florunner’) yields were not reduced when the crop was maintained free of Florida beggarweed [Desmodium tortuosum (Sw.) DC.] or sicklepod (Cassia obtusifolia L.) for 4 weeks after crop emergence and when vigorous crop growth was maintained for the remainder of the season. Sometimes weed-free maintenance for only 2 weeks resulted in near-normal yields, which indicated that the canopy of peanut leaves effectively suppressed the weeds. Conversely, these weeds had to compete with peanuts for more than 10 weeks before crop yield was reduced. Weeds that overtopped the peanuts at harvest emerged during the first 6 weeks after planting.

X-ray fluorescence analysis (XFA) is a new method for the spatial localization and quantification of herbicide residue on leaf surfaces. The distribution pattern of propanil (3′,4′-dichloropropionanilide) on the surface of prune (Prunus domestica L.) leaves sprayed to simulate drift is easily mapped using XFA. Residue distribution maps may be electronically enhanced. Enhancement does not qualitatively change the information content of the map when done with discretion.

Field studies indicated that liming an acid Bladen silt loam from pH 5.5 to 7.5 increased the phytotoxicity of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] and prometryn [2,4-bis-(isopropylamino)-6-methyoxy-s-triazine]. Liming greatly increased the persistence of atrazine, but did not affect prometryn dissipation. Liming increased the 14C-concentration present in the shoots of corn (Zea Mays L. ‘Pioneer 3369A’), cotton (Gossypium hirsutum L. ‘Coker 201’), and soybeans [Glycine Max (L.) Merr. ‘Ransom’] from soil treated with 14C-ring labeled atrazine, prometryn, and hydroxyatrazine [2-hydroxy-4-(ethylamino)-6-(isopropylamino)-s-triazine] in greenhouse studies. Decreases in 14C-uptake by the crops were associated with adsorption and degradation of the compounds in the soil. Atrazine was taken up in much greater amounts than hydroxyatrazine. Cotton absorbed less of the s-triazines than soybeans or corn from soil.

Analysis for total carbohydrate content was made on oven dried bermudagrass [Cynodon dactylon (L.) Pers.] dallisgrass (Paspalum dilatatum Poir.) and smutgrass [Sporobolus poiretii (R. & S.) Hitchc.] storage tissue collected at 2, 4, 6, or 36 weeks after fall treatment and at 2, 4, or 6 weeks after fall and spring treatment with three herbicides at varying rates. Those species that survived either fall or fall and spring herbicide application exhibited an initial reduction in carbohydrate content, but it returned to a level comparable to that in the untreated plants in most instances within 6 weeks after treatment. Atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] at 4.48 and 8.96 kg/ha and bromacil (5-bromo-3-sec-butyl-6-methyluracil) at 2.24 and 4.48 kg/ha resulted in carbohydrate reduction in bermudagrass and dallisgrass for no more than 6 weeks except where both fall and spring treatments were used. Smutgrass was controlled with these two herbicides within 2 weeks so that not enough live tissue was available for analysis. There was no carbohydrate reduction in bermudagrass with the 2.24, 4.48, or 8.96 kg/ha rates of MSMA (monosodium methanearsonate) beyond 2 weeks following treatment. The carbohydrate content of smutgrass was reduced up to 6 weeks after treatment with MSMA, and dallisgrass was controlled at all rates so that no carbohydrate analysis could be made.

Four field experiments were conducted to study the effects of row width, cultivation, soybean population, soybean cultivar, and herbicides on soybean [Glycine max (L.) Merr.] yields and control of common cocklebur (Xanthium pensylvanicum Wallr.). When the same herbicide practices were applied to all treatments, common cocklebur was controlled better in soybeans planted in 100-cm rows and grown with cultivation than in those planted in 18 or 33-cm rows and grown without cultivation. Increased soybean yields and better common cocklebur control were obtained when soybean populations were increased from 80,000 to 350,000 plants/ha. Common cocklebur reduced the yield of ‘Bragg’, one of the most competitive cultivars, 7% when grown in 100-cm rows with cultivation and 39% when grown in 33-cm rows without cultivation. The yields of six other cultivars were reduced about 20% in 100-cm rows and 32% to 52% in 33-cm rows. Cross cultivation controlled common cocklebur more effectively than did conventional cultivation in 100-cm rows, but cross cultivation was not advantageous when metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazine-5(4H)one] and bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] were applied.

Adsorption of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine], terbutryn [2-(tert-butylamino)-4-(ethylamino)-6-(methylthio)-s-triazine], and GS-14254 [2-(sec-butylamino)-4-(ethylamino)-6-methoxy-s-triazine] decreased on natural and limed soils as the soil pH increased to pH 8. More reduction in adsorption occurred with GS-14254 than with the other two herbicides. Increased toxicity to barley from GS-14254 was proportional to decreased adsorption by soils. Adsorption-desorption studies with Chehalis sandy loam (Cumulic Ultic Haploxeroll) indicated that extent and strength of adsorption were equivalent for GS-14254 (pKa 4.36) and terbutryn (pKa 4.32) at a soil pH of 5.20. Two soils, Boyce silt loam (pH 9.6, Cumulic Haplaquoll) and Crooked silt loam (pH 8.5, Xerolic Durorthid), adsorbed the s-triazines readily in contrast to the soils below pH 8. The high adsorption values were substantiated by the GR5 0 values on barley for atrazine and terbutryn, 10.2 and 13.2 kg ai/ha, respectively.

Glyphosate [(N-phosphonomethyl) glycine] was evaluated for three years as a foliar herbicide for the control of johnsongrass [Sorghum halepense (L.) Pers.]. In the greenhouse, maximum rhizome kill resulted from foliar applications of glyphosate at 1.12 to 2.24 kg/ha. In several field studies, plowing from 4 to 21 days following glyphosate application had little effect on johnsongrass control; plowing within 0.5 hr following glyphosate application resulted in less control than when plowing was delayed for 12 days. In stage of growth studies, control was better when glyphosate was applied to johnsongrass in the boot to full head stage than earlier when johnsongrass was 45 to 60 cm in height. In ‘York’ soybeans [Glycine max (L.) Merr.], glyphosate at 1.12 to 2.24 kg/ha applied 12 to 14 days prior to plowing and trifluralin (a,a,a-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) incorporated prior to planting provided good johnsongrass control. In ‘3369A’ corn (Zea mays L.) directed postemergence applications of glyphosate provided good johnsongrass control but caused extensive crop injury.

Freshly harvested Florida pusley (Richardia scabra L.) seeds do not germinate in continuous dark, but do germinate if exposed to more than 2 hr of light each day. Increasing periods of illumination up to 16 hr per day increases the germination percentages. Scarification increases the rate of germination in the presence of light. Scarification also causes germination of seeds stored for 8 months or longer in total darkness. The seeds fail to germinate at constant temperatures of 15 C or less and at 40 C. Almost complete germination occurs at a constant temperature of 30 C, or at alternating temperatures of 20 and 30 C. The seeds germinate equally well in the pH range of 3 to 8. Increasing depths of planting reduces percent emergence, and none of the seedlings emerge from a depth of 1.5 cm or more. Air-dried seeds can be stored either at 5 or at 25 C without losing viability, at least up to a period of 1 year after harvest. Moist storage of seeds at 5 C reduces germinability.

Single and repeated applications of MSMA (monosodium methanearsonate) with and without 2,4-D [(2,4-dichlorophenoxy)acetic acid], metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazine-5(4H)one], and methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-di-one] were evaluated for control of large crabgrass (Digitaria sanguinalis L. Scop.) and goosegrass (Eleusine indica L. Gaertn.). Large crabgrass was controlled satisfactorily at Griffin in 1972 and 1973 with a single application of 1.7 kg/ha of MSMA, however, repeated applications were required for similar control at Griffin in 1974 and at Blairsville in 1973 and 1974. Repeated treatments at 0.6 kg/ha resulted in satisfactory large crabgrass control in only 2 of 3 years at Griffin and 1 of 3 experiments at Blairsville. The optimum time interval between the first and second MSMA treatments (average 1973 and 1974) was 12 days for the 1.1 kg/ha rate and anytime between 12 and 19 days for the 1.7 and 2.2 kg/ha rates. There was no advantage in large crabgrass control from treatments of methazole, metribuzin, or combinations of MSMA + 2,4-D when compared with MSMA. Single applications of 1.1 kg/ha of metribuzin or 2.2 kg/ha of methazole resulted in excellent goosegrass control without causing any permanent injury to common bermudagrass [Cynodon dactylon (L.) Pers.]. Repeated treatments of 3.3 kg/ha of MSMA were required to obtain satisfactory goosegrass control.

Tolerance of sugarbeets (Beta vulgaris L. ‘Mono-Hy A1’) to ethofumesate (2-ethoxy-2,3-dihydro-3,3-dimethyl-5-benzofuranyl methanesulphonate) was associated with rate of application and soil type. Yield of roots was significantly reduced by preplant-incorporated applications of 3.4, 4.5, or 9.0 kg/ha of ethofumesate to a sandy loam soil, but only the 9.0 kg/ha rate reduced the yield on a loam soil. Pinto beans (Phaseolus vulgaris L. ‘Idaho #111’) yielded normally when planted on a sandy loam soil within 4 to 6 weeks after ethofumesate was incorporated at rates of 2.2 to 9.0 kg/ha. Corn [Zea mays L. ‘Pioneer brand 3773 MFS(N) hybrid’] yields were reduced in proportion to the rate of herbicide applied 3 weeks before planting. In greenhouse studies, barley (Hordeum vulgare L. ‘Moravian’) and wheat (Triticum aestivum L. ‘Scout’) were about 10 times more susceptible to soil residues of ethofumesate than corn. Concentrations of ethofumesate in the soil as low as 0.1, 0.2, and 1.5 ppmw reduced the height of wheat, barley, and corn, respectively.

One greenhouse and two field experiments were conducted to determine if crop protectants used in conjunction with herbicides would permit weed-free establishment of orchardgrass (Dactylis glomerata L. ‘Potomac’) with alfalfa (Medicago sativa L. ‘WL 307’). Herbicides used were EPTC (S-ethyl dipropylthiocarbamate) and butam [2,2-dimethyl-N-(1-methylethyl)-N-(phenylmethyl)propanamide] plus cyprazole {N-[5-(2-chloro-1,1-dimethylethyl)-1,3,4 thiadiazol-2-yl] cyclopropanecarboxamide}. These experiments revealed that banded activated charcoal allowed limited orchardgrass establishment with a herbicide but did not result in consistently better orchardgrass stands than the untreated control. Orchardgrass was not protected from herbicide injury by 1,8-naphthalic anhydride (NA) or R-25788 (N,N-diallyl-2,2-dichloroacetamide). The butam plus cyprazole mixture consistently controlled grass and broadleaf weeds as effectively as EPTC.

Butylate (S-ethyl diisobutylthiocarbamate), EPTC (S-ethyl dipropylthiocarbamate), vernolate (S-propyl dipropylthiocarbamate), diallate [S-(2,3-dichloroallyl)diisopropylthiocarbamate], CDEC (2-chloroallyl diethyldithiocarbamate), and chlorpropham (isopropyl m-chlorocarbanilate) at 0.1 kg/ha caused increased velvetleaf (Abutilon theophrasti Medic.) populations in field plots. Butylate caused increased populations of common lambsquarters (Chenopodium album L.) at rates of up to 1.1 kg/ha. In the laboratory, each of the six herbicides caused increased velvetleaf seed germination, and butylate, EPTC, and CDEC caused increased common lambsquarters germination when seeds were exposed to herbicide vapors prior to germination. Germination of velvetleaf, common lambsquarters, and giant foxtail (Setaria faberii Herrm.) was also increased by butylate solutions over a wide range of concentrations. Maximum germination stimulation generally occurred between concentrations of 10-5 and 10-6 M butylate. Seedling injury and death also resulted from these concentrations of butylate. Butylate stimulation of seed germination could not be correlated with light requirements of seeds, but appeared to be an additional promotive factor. Ungerminated common lambsquarters seeds after butylate treatment were viable and responded to KCN and KNO3 in the same manner as control seeds which did not initially germinate in water. Butylate in combination with the antidote, R-25788 (N,N-diallyl-2,2-dichloroacetamide) stimulated germination of common lambsquarters.

Inhibition of seedling growth and four assays for inhibition of photosynthesis were used to compare karbutilate [tert-butylcarbamic acid ester with 3-(m-hydroxyphenyl)-1,1-dimethylurea] with derivatives of karbutilate in which either the urea or carbamate side chain was missing. Karbutilate was a more potent, more presistent, and more specific inhibitor of photosynthesis than the phenylurea derivative fenuron (1,1-dimethyl-3-phenylurea) that would be formed by removal of the carbamate side chain. However, karbutilate did not exert the growth-inhibiting action observed for the alkyl carbamate derivative phenyl-N-tert-butylcarbamate, formed by removal of the urea side chain, which does not affect photosynthesis at concentrations below 10-3 M.

CBC (2,5-dichlorobenzoyl chloride) and MCB (methyl-2,5-dichlorobenzoate) function as plant growth regulators in a gaseous phase or in an aqueous solution. Sorghum [Sorghum bicolor (L.) Moench. ‘Martin’] and soybean [Glycine bicolor (L.) Merr. ‘Lee’] seeds were temporarily inhibited or delayed from germinating, but overcame the inhibition in time so there was no significant reduction in total germination. Seedlings produced from sorghum and soybean seed germinated and grown in aqueous solution of 35 μg/ml CBC or MCB were shorter and weighed less than control seedlings. Soybean seed treated with the vapors of CBC and MCB produced seedlings significantly reduced in dry weight as compared with that of controls. Foliar application of 500 or 1000 μg/ml of CBC significantly reduced the growth of soybean but not sorghum seedlings. Soybean seedlings treated with the vapors or an aqueous solution produced leaflets more narrow and thicker than control seedlings. A lethal response attributable to CBC or MCB was not recorded.