The movement and persistence of 4-amino-3,5,6-trichloropicolinic acid (picloram) in an Osborne clay soil was determined over a 4-year period. Picloram concentrations were determined with soybean (Glycine max (L.) Merr. ‘Altona’) as the bioassay plant. Application rates ranged from 35 to 700 g/ha. Movement and dissipation of picloram were neglible under low soil moisture conditions, but under high rainfall conditions picloram was leached into the 30 to 60-cm depth. A greater percent of the picloram was leached at the higher application rates. Dissipation increased with temperature (days over 27 C) and decreased with increasing depth in the soil profile. Two applications of picloram at 70 g/ha applied in 2 successive years showed no detectable accumulation, but accumulation occurred from two applications of 350 g/ha; 32% of the activity remained after approximately 2 years.

Foliar-applied 3-[p-(p-chlorophenoxy)phenyl]-1,1-dimethylurea (chloroxuron), chloroxuron with dodecyl ether polyethylene glycol surfactant, and dimethylamine salt of 4-(2,4-dichlorophenoxy)butyric acid (2,4-DB) effectively controlled cocklbur (Xanthium sp.) in soybeans (Glycine max (L.) Merr. ‘Hampton’ or ‘Lee’). While treatments caused crop injury, treated soybeans produced higher seed yields than untreated soybeans infested with cocklebur plants. Seed yields from soybeans growing free of cocklebur were not reduced by treatment with chloroxuron or chloroxuron with surfactant but in some cases were reduced by 2,4-DB treatment.

Bacterial production of CO2 from sucrose substrate increased growth of seven species of algae in CO2-limited laboratory cultures. Decomposition of organic matter in pond water also supplied enough CO2 to support good algal growth in cultures deprived of other sources of CO2. Estimates of CO2 production from decay of dissolved organic matter in six pond waters ranged from 0.32 to 3.53 mg/L per 24 hr. The carbonate-bicarbonate equilibrium system is a major source of CO2 for algal photosynthesis. However, in waters of low or extremely high alkalinity, this system will not support high rates of photosynthesis. In such waters CO2 from decomposition will stimulate photosynthesis. Decomposable organic compounds must be considered with nitrogen and phosphorus as factors responsible for accelerated eutrophication and nuisance algal blooms.

Greenhouse grown honey mesquite (Prosopis juliflora (Swartz) D.C. var. glandulosa (Torr.) Cockerell), huisache (Acacia farnesiana (L.) Willd.), and whitebrush (Aloysia lycioides Cham.) and field grown honey mesquite, huisache, whitebrush, live oak (Quercus virginiana Mill.), Arizona ash (Fraxinus velutina Torr.), and winged elm (Ulmus alata Michx.) were defoliated at several intervals following spray treatments with 4-amino-3,5,6-trichloropicolinic acid (picloram), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), or [(4-chioro-o-tolyl)oxy]acetic acid (MCPA). The time required by leaves to be retained on the plant after spraying to give maximum canopy reduction or death of plants varied among species. In most species, however, herbicide absorption and transport were complete within a 4-day period or less as compared to undefoliated treated plants.

The herbicide 3-amino-2,5-dichlorobenzoic acid (chloramben) was applied preemergence to soybeans [Glycine max (L.) Merr.] in 1969, 1970, and 1971. Herbicide band widths were 18, 36, and 53 cm, and there was a broadcast treatment. Cultivation and rotary hoeing were also imposed on the herbicide band widths as variables. A 36-cm band of chloramben was the minimum band width used which consistently maintained soybean yield when supplemented with mechanical tillage. Broadcast treated soybeans without mechanical tillage yielded as well as handweeded soybeans in 2 of 3 years. Each 4 kg/ha of weed growth reduced soybean yield 1 kg/ha. Average weed yield reduction due to cultivation was 100, 76, and 54% in 1969, 1970, and 1971, respectively, when average weed yields were 360, 1650, and 4720 kg/ha in successive years. Rotary hoeing reduced weed growth 48% and increased soybean yield 20% in 1970 but did not significantly affect weed or soybean yields in 1969 and 1971.

The total quantity and concentration of six herbicides, isopropyl m-chlorocarbanilate (chlorpropham), 2-chloro-4-(ethylamino)-6-(isopropylamino-s-triazine (atrazine), 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (linuron), 2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide (alachlor), 3-amino-2,5-dichlorobenzoic acid (chloramben), and (2,4-dichlorophenoxy)acetic acid (2,4-D), in unaerated, aqueous solutions absorbed by seeds of 11 soybean (Glycine max (L.) Merr.) strains were measured. Mechanism of movement of the herbicides from the aqueous solutions to the seeds in the experimental procedure employed was diffusion. Total quantity and concentration of herbicide found in the seeds differed significantly for both herbicides and soybean strains. Total quantity of herbicide absorbed was determined by total oil and percent oil of the seeds. The capacity of the seeds to absorb a given herbicide was more closely related to percent oil of the seeds than to total oil of the seeds. The emergence and seedling shoot weight of ‘Cutler’ soybeans were not affected appreciably by concentrations of linuron, atrazine, and chloramben (potassium salt) but were reduced by high concentrations of chlorpropham and alachlor and relatively low concentrations of 2,4-D (potassium salt) in the seeds.

Two herbicides, the alkanolamine salts of 2-sec-butyl-4,6-dinitrophenol (dinoseb) and 3-[p-(p-chlorophenoxy) phenyl]-1,1-dimethylurea (chloroxuron), were compared for their effects on soybean [Glycine max (L.) Merr., ‘Lee’] when applied topically. In initial studies, chloroxuron was damaging when applied twice to soybean and reduced yields in one of the two year's studies. In a third year's work, direct comparisons of topical applications of dinoseb and chloroxuron showed that soybean injury increased with increased rate of material at each soybean growth stage with the most severe initial damage in the two-trifoliate stage. Recovery was rapid with few significant yield decreases occurring. Chloroxuron was more effective in controlling the broadleaf weeds present. Both herbicides were most effective when weeds were in the seedling stage of growth.