The growth of soybean (Glycine max (L.) Merr.) seedlings was retarded when treated with either methyl 3-amino-2,5-dichlorobenzoate (amiben methyl ester) or α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) when compared with soybeans treated with either 3-[-p-(p-chlorophenoxy)phenyl]-1,1-dimethylurea (chloroxuron) or 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea linuron. Seedling growth of soybeans also was retarded when treated with amiben methyl ester alone or applied in combination with O,O-diethyl S[2-(ethylthio)ethyl] phosphorodithioate (disulfoton). Insecticides did not influence growth of soybeans. Linuron applied in combination with O,O-diethyl S-[(ethyl-thio)methyl] phosphorodithioate (phorate). or methyl-N-[(methylcarbamoyl)oxy] thioacetimidate (methomyl) and amiben ester applied in combination with phorate produced significantly lower seedling vigor during only 1 year than when each pesticide was applied alone. Soybean stands were significantly lower only in 1 year when linuron was applied in combination with methomyl. None of the pesticides applied alone or in combination caused significant differences in date of maturity, lodging, seed yield, seed size, or seed quality during either year.

Sixty percent of the roots of sugarbeets (Beta vulgaris L.) at harvest were aberrant in the zone of the hypocotyledonary neck when 0.84 kg/ha of α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) was sprayed primarily on the hypocotyledonary tissues of seedlings in the 10 to 12-leaf stage, compared to 7% when soil surrounded most of the hypocotyledonary tissues at the time of application. Trifluralin did not reduce the yield of roots or kilograms of sucrose per hectare in either treatment. Sucrose content and purity were lower, and total nitrogen was more than twice as high in sections of neck and root tissues where the aberrations were the most severe as compared to normal sections of neck and root tissues from the untreated plots. In the greenhouse, trifluralin inhibited the growth of primary and lateral roots in sugarbeet seedlings.

The uptake and release of 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) by green sunfish (Lepomis cyanellus Raf.) were measured during a 3-week exposure to either non-labeled or symmetrically ring-labeled 14C-simazine. Exposure was by feeding (3 and 10 mg/kg body wt) or bath (1 and 3 ppm). To determine the retention of simazine, treated fish remaining after exposure and sampling were placed in fresh water for 4 weeks. This water was changed weekly. Fish in the bath absorb simazine in amounts directly proportional to the concentration in the water: i.e., 0.95 and 2.29 ppm total residue after 3 weeks exposure to 1.0 and 3.0 ppm, respectively. Little or no simazine was found in feed-exposed fish 72 hr after feeding. Almost all of the residue was in the viscera. No simazine residue was detected in fish from the water bath exposure after they had been in fresh water 7 days.

Interactions between carbamate and growth regulator herbicides were antagonistic both in whole plants and in plant segments. When combinations of isopropyl m-chlorocarbanilate (chlorpropham) and (2,4-dichlorophenoxy)acetic acid (2,4-D) were applied to the foliage of either redroot pigweed (Amaranthus retroflexus L.) or pale smartweed (Polygonum lapathifolium L.), the severe twisting effects of 2,4-D were greatly reduced. This interaction did not involve differential movement or metabolism of either herbicide. The induced elongation of soybean hypocotyl sections by the three growth regulators 2,4-D, 3,6-dichloro-o-anisic acid (dicamba), and 4-amino-3,5,6-trichloropicolinic acid (picloram) was inhibited in the presence of either chlorpropham or S-ethyl dipropylthiocarbamate (EPTC). Similarly, curvature tests using soybean (Glycine max (L.) Merr.) hypocotyl sections showed the curvature induced by the growth regulators to be almost completely eliminated by the presence of the carbamates.

Total nonstructural carbohydrate (hereinafter referred to as TNC) storage in roots and utilization of TNC by yellow rocket (Barbarea vulgaris R. Br.), white cockle (Lychnis alba Mill.), and hoary alyssum (Berteroa incana (L.) DC) was studied through a 1-year life cycle in plants seeded July 8, July 22, and August 5, 1966. For yellow rocket, TNC storage was most rapid during September and reached maximum levels by November 2. Younger plants stored TNC more efficiently than did older plants, but total grams of TNC per plant were greater for older plants than for younger plants. No plants bolted during the seeding year. Rapid declines in TNC of the roots began in late March, and minimum TNC levels coincided with the completion of flowering in mid-June for all plants the year after seeding. For white cockle, TNC storage was most rapid during September and early October, and reached maximum levels for all plants by November 2. There was no apparent winter injury to any of the plants. Total growth in 1967 was greatest for plants seeded July 8 and least for plants seeded August 5. Flowering began June 2 and seed were mature June 29. Adventitious buds were present on the roots of all plants on all sampling dates from September 7, 1966, through July 7, 1967. Minimum levels of TNC during spring growth were reached in mid-June. For hoary alyssum, TNC storage was most rapid during late September and October and reached maximum levels by the middle of November. TNC levels were higher in plants seeded July 22 or August 5 than in those seeded July 8. Plants seeded July 8 were flowering profusely by the middle of September, those seeded July 22 were flowering October 6, but those seeded August 5 did not flower in the seeding year. In 1967, all plants were in full bloom May 26. Minimum TNC levels were reached at full bloom and there was no accumulation of TNC as of July 7.

Cotton (Gossypium hirsutum L.) grown at two locations in Alabama from 1966 to 1968 produced maximum yields when kept free of annual weeds for approximately 8 weeks after emergence. Weed control for longer periods failed to increase yields. When initial weed control measures were delayed until 6 to 7 weeks after emergence at one location and 4 to 5 weeks at the other location, cotton was not injured. Prolonged weed competition past the critical periods usually resulted in drastic cotton yield reductions. Plant height and stem diameter of cotton were reduced by some of the weed competition treatments.

We measured some of the more important biologic and microclimatic parameters of the functional environment of downy brome (Bromus tectorum L.) communities during the establishment period of seedlings of intermediate wheatgrass (Agropyron intermedium (Host) Beauv., var. Amur). These measurements were made in relation to weed control and seeding treatments. Weed growth and establishment of replacement vegetation were directly related to available soil moisture and favorable temperatures in the immediate environment of growing plants. Lack of available soil moisture during critical periods of the growing season was the major deterrent to seeding success. The limited precipitation stored as soil moisture was available to perennial grass seedlings where weeds were controlled. Without weed control, growth of downy brome preempted the effective precipitation, and moisture became limiting for growth of perennial grass seedlings. Seeding in furrows, along with weed control, further improved moisture conditions for the seedlings. Also, use of furrows enhanced seedling growth by lowering maximum air and soil temperatures in the seedlings' immediate environment.