In laboratory studies, the herbicide 3'-chloro-2-methyl-p-valerotoluidide (solan) when applied to soil was transformed in part to 3,3'-dichloro-4,4'-dimethylazobenzene. The biochemically mediated transformation followed the pattern established previously for 3,4-dichloroaniline-based acylanilides, but the 3-chloro-4-methylaniline intermediate did not accumulate. Compared to 3,4-dichloroaniline-based acylanilides, solan yielded less azo residue and did not inhibit soil respiration, even if applied at 200 times the recommended field rate.

Postemergence applications of 0.5 and 1.0 lb/A of a potassium salt of 4-amino-3,5,6-trichloropicolinic acid (picloram) killed all or nearly all of the goldenrod (Solidago nemoralis Ait.) growing with timothy (Phleum pratense L.). Two lb/A of butoxy ethanol ester or dimethylamine salt of (2,4-dichlorophenoxy)acetic acid (2,4-D), and 1 and 2 lb/A of butoxy ethanol ester of 4-(2,4-dichlorophenoxy) butyric acid (2,4-DB) reduced yields of goldenrod 75 to 95%. Lower rates of herbicides were relatively unsatisfactory for controlling goldenrod. Timothy was not injured by the herbicides and yields increased 0.8 and 1.0 lb for each 1.0 lb of weeds that failed to grow.

Greenhouse and growth chamber studies were conducted to investigate effects of herbicide placement in soil on toxicity to emerging seedlings. The use of a technique involving a plastic bag over the plants for 3 to 4 weeks to reduce soil moisture loss did not change the apparent site of 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) uptake by green foxtail (Setaria viridis (L.) Beauv.) or oats (Avena sativa L.). Atrazine was more effective on oats through root exposure and more effective on green foxtail through shoot exposure when an untreated buffer zone around the seed was used. But in subsequent studies without the buffer zone, atrazine was most active when placed immediately below the seed of both oats and green foxtail. Proximity to the seed increased effectiveness of atrazine, S-ethyl dipropylthiocarbamate (EPTC), and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron). Also, a narrow concentrated layer of these three herbicides adjacent to the seed was more effective than a wider dilute layer above or below the seed. A diurnal fluctuating temperature regime with a low night temperature increased toxicity of EPTC to oats through root exposure, when compared to a constant temperature regime.

A modification of an 8-ft, self-propelled combine for harvesting research plots of soybeans (Glycine max L.), sorghum [Sorghum bicolor (L.) Moench], and small grains is described. The combine facilitates efficient and precise harvesting of yield plots with considerable savings in time and labor.

Studies conducted from 1964 to 1967 on three soil types indicated that α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin), dimethyl tetrachloroterephthalate (DCPA), and 4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline (nitralin) applied preplant and incorporated with two tandem diskings in March or April prior to bedding, gave excellent control of a mixture of Amaranthus sp. and volunteer sorghum (Sorghum bicolor (L.) Moench) in cotton (Gossypium hirsutum L.) planted in early May. Cotton was not stunted and yields were not appreciably reduced. When trifluralin was applied, soil residues the next year dictated that sorghum planting be delayed until May.

The volatilization of α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) from a Miller clay and commercial sand was determined by analysis of air samples above the soils. The method requires no extraction of soil or traps and is sensitive to approximately 8 ppm of trifluralin in air. The loss of trifluralin was influenced more by soil moisture than by soil type. Data indicated that trifluralin vapors in air are photolytically degraded. Similar studies were conducted with 4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline (nitralin), but volatilization was so slow that detectable concentrations of this herbicide did not occur.

More 4-amino-3,5,6-trichloropicolinic acid (picloram) was detected in soil samples by soybean (Glycine max (L.) Merr., var. Ford) bioassay when the herbicide was applied in the fall than when it was applied in the spring to several pasture types. Downward movement was greater in sandy loam than in silty clay loam. Dissipation of picloram was greatest in the upper 12 inches regardless of soil type. More picloram was detected in the 24 to 36-inch depth from plots treated 1, 2, or 3 years before sampling than in plots sampled the year of treatment. This indicated downward movement into the subsoil.

Field studies were conducted during 1967 and 1968 at the University of Wisconsin Experimental Farm, Arlington, Wisconsin, to determine the comparative effectiveness of combinations of row spacings and rates of 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (linuron) for control of yellow foxtail (Setaria glauca (L.) Beauv.) and barnyardgrass (Echinochloa crusgalli (L.) Beauv.) in soybeans (Glycine max (L.) Merr.). Soybean yields and weed control increased as row spacing decreased. Lower rates of linuron were required for comparable weed control as row spacing decreased. Yield increases with decreasing row width were much greater in 1968 than in 1967, probably because of better rainfall during July, August, and early September in 1968. Improved weed control in the narrow rows may have been due partially to absorption by soybean leaves of light wavelengths that may be most favorable for photosynthesis and vegetative growth of some weed species.

The phytotoxicity of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), 1,1-dimethyl-3-(α,α,α-trifluoro-m-tolyl)urea (fluometuron), 3-(hexahydro-4,7-,methanoindan-5-yl)-1,1-dimethylurea (norea), and 2,4-bis(isopropylamino)-6-(methylthio)-s-triazine (prometryne) to cotton (Gossypium hirsutum L., var. Acala 4-42) was compared. Warburg experiments indicated that fluometuron and norea inhibited photosynthesis in isolated leaf disks to a much smaller extent than did diuron and prometryne. When the plants were grown in solution culture, diuron and prometryne were much more phytotoxic to cotton than fluometuron and norea, whereas when grown in soil, prometryne was the least phytotoxic, followed by norea, fluometuron, and diuron. Results of experiments on root vs. shoot uptake showed that all four herbicides entered the cotton seedlings through the roots, and no injury occurred to cotton when the compounds were applied to the shoot zone only. Norea and fluometuron were much more leachable than prometryne and diuron. These results indicate that depth protection in the soil, in addition to translocation and metabolism, might account partially for the tolerance of cotton to preemergence application of the tested herbicides.

Effects of sub-acute levels of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) on bluegill sunfish (Lepomis macrochirus Rafinesque) were assessed in a pond environment. Eight 0.1-A earthen ponds were each stocked with 300 bluegill fingerlings and treated once with diuron wettable powder at 0, 0.5, 1.5, and 3.0 ppmw, two ponds per treatment level. Dissolved oxygen was reduced severely in some pond waters 2 days following treatment and the low level persisted for 3 to 4 days. Gill lamellae were ruptured and hemorrhagic in 20% of the fish from the 3.0 ppmw ponds at 3 days post-treatment. Fish in a cage succumbed during this period in a 3.0 ppmw pond. No further bluegill mortality was observed in treated ponds 3 days after treatment. Hematocrit measurements of treated and control fish could not be correlated with treatment level. Best growth was exhibited by control fish and their progeny. Diuron residues were not detectable in treated pond waters after 28 days. Residues of diuron in treated-pond vegetation were detectable up to 95 days following treatment, whereas residues in mud were measured by gas chromatography 122 days after treatment. Invertebrate populations increased in all ponds with time, indicating little or no effect of the herbicide on their numbers. Good control of filamentous algae and vascular aquatic vegetation was demonstrated in the treated ponds.

Shoots of naturally established specimens of turkey oak (Quercus laevis Walt.) 3 to 6 ft high were treated with 4 to 8 lb aehg of a commercial concentrate formulation of the butoxyethanol ester of (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T) on or about May 1, June 1, July 1, August 1, and September 1. Foliar applications were made to the point of run-off and foliar-basal treatments were made first to the basal 8 inches of the main stem and then to the lower four-fifths of the remainder of the shoot. The objective was to assess the utility of number two diesel fuel as an additive for such treatments when the oil was used at rates of 0, 5, 10, and 20% in the final formulations. The experiment was repeated in 3 different years. Responses measured approximately 11, 14, and 23 months after initial treatment were percent control of original shoots, percent control of new shoots, shoot height, and number of live stems/plant. Foliar treatments without oil were progressively less effective as they were made later in the growing season. The addition of oil to foliar treatments provided more effective control of the original shoots and greater reduction in shoot heights, especially when the oil concentration was 20%. The foliar-basal method was notably ineffective in the absence of oil. Addition of oil to the foliar-basal treatments provided marked improvement in the original shoot, total shoot control index, shoot height, and stems/plant responses, especially at the 20% level of oil. Diesel fuel is useful as an additive for 2,4,5-T sprays to be applied to turkey oak, especially where treatment is to be made in the latter half of the growing season and in particular where the lower stems can be treated.

The degradation of 14C ring-labeled 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) was studied in the laboratory with four Hawaiian soils selected for their wide range of organic matter contents (4 to 29%), pH values (4.4 to 6.3), and different mineralogies. Atrazine concentrations of 1, 5, 10, 50 and 100 ppmw in soils incubated at 30 C gave similar 14C-recovery curves. Degradation was rapid in all four soils; atrazine recovery at 34 days (30 C) ranged from 15 to 30% of the quantity applied. Degradation was accelerated by a temperature increase from 30 to 50 C, suggesting a chemical rather than a biological process. The loss of atrazine from soils approached a first order reaction rate at 30 C, and deviated from this at 50 C. Hydroxyatrazine was the main degradation product with only a slight amount of an unidentified “Product B”. It was concluded that chemical degradation (hydrolysis) was the major pathway of atrazine loss in these soils. This process was more closely related to pH, i.e. faster on low pH soils, than with organic matter content or adsorption. The fraction of atrazine adsorbed on soil increased with the decrease in total atrazine caused by degradation. Extraction of soils with both water and methanol and subsequent analysis of extracts by thin-layer chromatography showed that some of the methanol-extractable atrazine was not readily desorbed by water. These results indicate that some of the residual atrazine extracted chemically may not be available for uptake by plants and would be relatively immobile in soil water.

The concept of herbicide partition into adsorbed and solution phases in the soil was utilized to predict the effect of soil water content on the concentration of herbicide in solution. Calculated predictions based on measured partition coefficients and water contents were tested experimentally by equilibrating 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) with soil from three horizons of a latosolic soil at four water contents (45 to 60%). The effects of adsorption and water content were predicted with reasonable accuracy when only that water held at tensions less than 15 bars was considered available for equilibration with the applied herbicide. Only on low adsorption soils will water content variations alter significantly herbicide concentration in the soil solution. The principal effect of soil water content on herbicide phytotoxicity probably is associated with herbicide transport, which is more sensitive to changes in water content than is the concentration of herbicide in soil solution.

Residual herbicidal action of 3-amino-2,5-dichlorobenzoic acid (amiben), the methyl ester of amiben, 3-acetamido-2,5-dichlorobenzoic acid (N-acetyl amiben), 3-propionamido-2,5-dichlorobenzoic acid (N-propionyl amiben), 3-benzamido-2,5-dichlorobenzoic acid (N-benzoyl amiben), and the methyl ester of N-benzoyl amiben after 0, 1, 2, 4, and 6 hr irradiation was measured by oats (Avena sativa L., var. Markton) bioassay. In a greenhouse study, amiben and N-benzoyl amiben were applied to the soil surface, exposed to sunlight for 7.5 hr, and similarly bioassayed. Amiben, the methyl ester of amiben, and N-acetyl amiben lost 40 to 60% of their original herbicidal activity after 2 to 4 hr irradiation in the laboratory. N-benzoyl amiben and its methyl ester retained over 90% of their activity after 6 hr irradiation. Solar illumination reduced the herbicidal activity of amiben applied to the surface of wet soil by 11 to 14% but had no effect on N-benzoyl amiben. On a dry soil, the losses of amiben and N-benzoyl amiben were not significant.

We studied changes in the concentration of 4-amino-3,5,6-trichloropicolinic acid (picloram) with time in roots, stems, and leaves of 20-day-old seedlings of huisache (Acacia farnesiana (L.) Willd.) and honey mesquite (Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell). Exposing root systems to aqueous solutions of picloram (1.0 ppm huisache and 10.0 ppm honey mesquite) for 24 hr killed approximately 60% of the treated plants. In honey mesquite, picloram was redistributed and eventually lost over a 5-day period, whereas neither redistribution nor loss occurred in huisache.

The uptake, translocation, and fate of (2,4-dichlorophenoxy)acetic acid (2,4-D) were compared in nightflowering catchfly (Silene noctiflora L.) and common lambsquarters (Chenopodium album L.), resistant and susceptible species, respectively. Nightflowering catchfly leaf sections absorbed more 2,4-D from 5 × 10-4 M and 5 × 10-6 M 2,4-D solutions at pH 3.0 than did leaf sections of common lambsquarters. Intact plants of both species accumulated 2,4-D in the stems and leaves below the treated leaf. At 72 hr after treatment, nightflowering catchfly released 2,4-D through the roots into the nutrient solution while common lambsquarters continued to accumulate 2,4-D. Nightflowering catchfly metabolized 2,4-D and the metabolite was recovered in the roots 24 hr after treatment, whereas common lambsquarters did not metabolize 2,4-D.

Lithium salt of (2,4-dichlorophenoxy)acetic acid (2,4-D) (1000 ppm) was sprayed on plants of curly dock (Rumex crispus L.) 12 days before anthesis, at an thesis, 7 days after anthesis, and 34 days after anthesis. Treatment 12 days before anthesis completely prevented the formation of viable seeds. Two percent of the seeds had minute embryos after treatment at anthesis, but even these seeds did not germinate. Embryos were present in 91% of the seeds from plants treated 7 days after anthesis. These embryos ranged in size from 0.5 to 2.5 mm. The total weight of seeds obtained was significantly less than the control and only 5 to 15% of these seeds were capable of germination. Spraying the inflorescences 34 days after anthesis did not affect the number of seeds produced or seed viability. Almost all plants remained alive after the harvest.

Neutron-activation analyses of arsenic were reproducibly quantitative at 10 ng As and might be extended as low as 3 ng As with extended counting periods. The method was tested on soil and cotton (Gossypium hirsutum L., var. Atlas 67) leaves treated with repeated applications of monosodium methanearsonate (MSMA). Leaves from untreated plants contained 55 ng As/g whereas leaves from treated plants showed higher levels of arsenic. Translocation of As was demonstrated and analysis of arsenic in the soil was valid.

Granular 4-amino-3,5,6-trichloropicolinic acid (picloram) was effective in controlling live oak (Quercus virginiana (Mill.), huisache) (Acacia farnesiana (L.), Willd.), and yaupon (Ilex vomitoria Ait.), but not honey mesquite (Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell) in south Texas. Granular 5-bromo-3-sec-butyl-6-methyluracil (bromacil) controlled live oak and huisache. Herbicides applied to soil were usually most effective in spring and fall during periods of active brush growth. Picloram granules applied in May to a mixed stand of woody plants in Puerto Rico usually were effective. However, rates up to 30 lb/A were ineffective on some species.

Four substituted pyridazinone compounds inhibited the Hill reaction and photosynthesis in barley (Hordeum vulgare L., var. Dayton C.I. 9517). These inhibitions appeared to account for the phytotoxicity of 5-amino-4-chloro-2-phenyl-3(2H)-pyridazinone (pyrazon). The pyridazinone chemicals were weaker inhibitors than 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine). Two substitutions onto the molecular structure of pyrazon result in a new experimental herbicide, 4-chloro-5-(dimethylamino)-2-(α,α,α-trifluoro-m-tolyl)-3(2H)-pyridazinone (hereinafter referred to as 6706), which retains the action mechanism of pyrazon but also has two additional biological properties. It is resistant to metabolic detoxication in plants, and it possesses a second mode of action involving interference with chloroplast development. The second action is like that expressed by 3-amino-s-triazole (amitrole) and by 3,4-dichlorobenzyl methylcarbamate (dichlormate). However, the new chemical is 100 to 1000 times more effective. The trifluoromethyl substitution on the phenyl ring and the dimethyl substitution on the amine are both required to give either of the two additional physiological properties. Analogs with only one of the two substitutions behave like pyrazon rather than like 6706.