Competition studies were conducted with soybeans Glycine max. (L.) Merr. ‘Clark 63’ and Venice mallow (Hibiscus trionum L.). One Venice mallow per 7.5 cm of soybean row reduced soybean seed yield 632 kg/ha after 85 days competition. Thirty to 40-cm weed bands in and between soybean rows reduced yields 270 to 651 kg/ha with 35 to 40 days of competition. A natural stand of 215 Venice mallow plants per square meter reduced soybean yield 454 kg/ha after 30 days of competition, and competition up to 110 days reduced yield as much as 1490 kg/ha. Weed competition affected the number of pods per soybean plant more than any other seed-yield component, and soybean height was reduced. Soybean yields were reduced more when soil moisture was abundant early in the growing season and limited in late summer than when moisture was limited early in the growing season and above average until soybeans matured.

Absorption of the butyl ether esters of (2,4,5-trichlorophenoxy)-acetic acid (2,4,5-T) by honey mesquite [Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell] foliage was more rapid when 0.56 kg/ha was applied in 15 L/ha paraffin oil than when diesel oil, water, or emulsions of the oils in water were used as carriers. However, carrier had little effect on 2,4,5-T translocation to stems or roots. The percentage of greenhouse-grown honey mesquite plants killed was reduced when 2,4,5-T was applied in diesel oil as compared to other carriers studied.

Five fallow treatments in an alternate winter wheat (Triticum aestivum L.) fallow rotation experiment were compared over a 6-yr period at North Platte, Nebraska. During the 14-month fallow period from winter wheat harvest until winter wheat planting, plots receiving no tillage (weeds were controlled by herbicides) had the least weed growth, most soil water stored, and highest amount of surface mulch maintained. Also, the plots receiving only herbicides had the highest grain yields of all treatments. However, an average of 3.8 herbicide applications were needed to control grass weeds missed by 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) during the last 5.5 months of the fallow period. Greatest weed growth during the fallow period was on plots that received only tillage and occurred during the first 3 months after harvest.

In preliminary greenhouse evaluations and then in field studies, common cocklebur (Xanthium pensylvanicum Wallr.) and wild common sunflower (Helianthus annuus L.) were controlled by early postemergence applications of 3,5-dibromo-4-hydroxybenzonitrile (bromoxynil). Bromoxynil on young soybeans [Glycine max (L.) Merr.] caused temporary necrosis, retarded growth, and delayed maturity but did not reduce the stand of soybeans. Subsequent recovery and final yields of treated soybeans were such that selective control of common cocklebur and wild common sunflower appeared feasible. Treatments were applied as aqueous sprays over the tops of both the weeds and the crop. Rates of 140 or 196 g/ha were sufficient to control common cocklebur or wild common sunflower that was in the six true-leaf stage or smaller. In terms of soybean development, the optimum time for treatment appeared to be about the first trifoliolate stage.

The herbicide mixture 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) + 2-chloro-N-isopropylacetanilide (propachlor) was applied preemergence broadcast and in band widths of 18, 36, and 53-cm to corn (Zea mays L.). All herbicide treatments were applied as 1.1 kg of atrazine + 2.7 kg of propachlor per treated hectare. One row-middle cultivation and one rotary hoeing were also imposed on the herbicide treatments as variables. The 18-cm band of atrazine + propachlor with supplementary cultivation was as effective in controlling weed growth and maintaining corn yield as were wider herbicide bands or a broadcast treatment. Broadcast treated corn without row-middle cultivation produced significantly less grain than the handweeded check both years of the experiment. The average ratio of weed dry weight to reduction in corn yield was 0.8 to 1. Cultivation of row middles reduced average end-of-season weed yields 80%. Cultivator effectiveness on an 18-cm herbicide band equalled that measured on wider herbicide bands. Rotary hoeing reduced early season weed yields 82 and 38% in 1970 and 1971, respectively.

When the mixture of 3.4 kg/ha of S-ethyl N-ethylthiocyclohexanecarbamate (cycloate) plus 1.1 kg/ha of 3′-hydroxypropionanilide isopropylcarbamate (R 11913) was applied to three soils before planting sugarbeets (Beta vulgaris L.), the average stand of kochia (Kochia scoparia (L.) Schrad.) was reduced by 89% as compared to 9% with the standard rate of 4.5 kg/ha of cycloate. The competition of foxtail millet (Setaria italica (L.) Beauv.), redroot pigweed (Amaranthus retroflexus L.), and kochia was nearly eliminated throughout the growing season by a combination of 3.4 kg/ha of cycloate plus 1.1 kg/ha of R 11913 applied preplanting and 0.84 kg/ha of methyl m-hydroxycarbanilate m-methylcarbanilate (phenmedipham) applied postemergence. This combination of treatments minimized competition from weeds all season, and the yield of sucrose was within 8% of that of the handweeded plots. Residues of the mixture of cycloate plus R 11913 were not detected biologically in two soils 8 months following application.

Sprayed aqueous emulsions of long chain amine salts of (2,4-dichlorophenoxy)acetic acid (2,4-D) penetrated faster into sunflower (Helianthus annuus L. ‘Peredovik’) leaves than did sprayed dimethylamine salt aqueous emulsions at 21 C and 5% relative humidity (RH). The initial absorption (65 to 70% in 13 hr) was independent of light, but the following much slower absorption was strongly light dependent. The long-chain amine salts sprayed in diesel oil as carrier were 90% absorbed in 4 hr. It was concluded that long chain amine salts should be sprayed in this carrier to facilitate penetration into leaves and to reduce possible environmental contamination.

Herbicide treatments were applied to established alfalfa (Medicago sativa L.) in 1969 and 1970 to determine winter annual weed control efficacy, crop tolerance, and influence on alfalfa yield and protein. Common chickweed (Stellaria media (L.) Cyrillo) was the predominant species in both years. Excellent weed control was achieved in 1969 with 2-sec-butylamino-4-ethylamino-6-methoxy-s-triazine (GS 14254) at 1.7 kg/ha, 2-[[4-chloro-6-(ethylamino)-s-triazin-2-yl]amino]-2-methyl-propionitrile (cyanazine) at 4.5 kg/ha, 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) at 1.7 kg/ha, and 3-tert-butyl-5-chloro-6-methyluracil (terbacil) at 1.1 kg/ha. Several other treatments also significantly reduced weed yields. All herbicides significantly reduced weed yields in 1970. First harvest alfalfa yields in 1969 were not increased significantly despite the excellent weed control afforded by several treatments. Second harvest alfalfa yields did not differ significantly, however, weeds were not a problem in the regrowth. In 1970 four of the 19 treatments did yield significantly more than control plots. Alfalfa protein was not altered by any of the treatments either year.

Equimolar concentrations of 4-phenylsulfonyltrifluoromethanesulfono-o-toluidide (hereafter referred to as MBR-8251), S-ethyl dipropylthiocarbamate (EPTC), and 2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide (alachlor) were compared using a quartz gravel nutrient culture method for detecting toxicity to yellow nutsedge (Cyperus esculentus L.), okra (Hibiscus esculentus L.), cabbage (Brassica oleracia var. captata L.), cucumber (Cucumis sativus L.), and flax (Linum ustitatissimum L.). MBR-8251 was more active on yellow nutsedge than EPTC or alachlor, and MBR-8251 treated nutlets were controlled for a longer period. In general, crops were more tolerant of MBR-8251. Field studies comparing the effectiveness of MBR-8251 to EPTC, S-propyl dipropylthiocarbamate (vernolate), 2-chloro-4-(ethylamino)-6-isopropylamino-s-triazine (atrazine), 3-isopropyl-2,1,3-benzothiazinone-(4)-2,2-dioxide-6,7,8 (BAS-3510), alachlor, and 2-chloro-N-(ethoxymethyl)-6′-ethyl-o-acetotoluidide (MON-097) indicated that after 10 weeks yellow nutsedge control was excellent with MBR-8251, MON-097, and alachlor.

Only 24% of black seed of halogeton (Halogeton glomeratus (M. Bieb.) C. A. Mey.) germinated 2 weeks after collection in October. After 11 weeks of dry storage germination had increased to 60%. During the additional 12 weeks of pregermination treatment, germination did not vary significantly from 60% except for seed stored moist at low temperatures. Ninety to 95% of moist seeds stored at −6 C for 6 weeks or longer germinated within 48 hr; this rate of germination was superior to that of seed collected in December.

A new method was developed for incorporating herbicides into the root zone of saltcedar (Tamarix pentandra Pall.) in arid, low rainfall areas. A spray pipe with five nozzles was mounted along the rear edge of a 2.44-m root plow blade. A supply line connected the spray pipe with a sprayer mounted on the plow frame. In operation, the saltcedar roots were severed at a selected depth by the blade as herbicide was sprayed simultaneously into the cut-root zone. A similar root plow with a 1.22-m blade was designed for use on small research plots.

In comparative evaluation of adjuvant effects in eight species, nonionic silicone-glycol surfactants enhanced the activity of six herbicides to a greater extent than a standard organic surfactant, whereas cationic amino silicone surfactants enhanced to a lesser extent. The efficacy of the nonionic silicones was associated with (a) a greater enhancing action in species, particularly grasses, that were relatively resistant to herbicides applied without adjuvants and (b) a greater ability to enhance herbicides with very low water solubility. The cationic silicones in combination with some of the herbicides provided less enhancement in moderately sensitive crops than did the standard organic surfactant but provided equivalent enhancement on some weeds. The threshhold concentration for enhancement by silicone-glycols was 0.01% in a susceptible species and 0.1% in a resistant species. In yellow nutsedge (Cyperus esculentus L.), a silicone-glycol surfactant at a concentration of 0.5% provided greater enhancement of several herbicides than any of three organic surfactants or an emulsifiable oil.

Two clones of field bindweed (Convolvulus arvensis L.) which differed in their susceptibility to (2,4-dichlorophenoxy)acetic acid (2,4-D) under field and greenhouse conditions also exhibited similar differences when stem cells were cultured in liquid and agar media. Amino acids added to the culture media altered the response to 2,4-D. Glutamic acid increased the tolerance of the susceptible (S) clone, but reduced the tolerance of the resistant (R) clone. Glutamine increased the susceptibility of the S clone to a much greater degree than it did the R clone. No significant differences were noted in the rates of absorption of metabolism of 2,4-D by the two clones. Glutamine increased and glutamic acid decreased 2,4-D absorption by both clones. Levels of nitrate reductase activity (NRA), soluble protein (SP), and gross RNA (GR) increased in the S tissues but decreased or remained constant in the R tissues exposed to 4.5 × 10−5M 2,4-D. Correlations between 2,4-D susceptibility and NRA demonstrated a relationship between the effects of 2,4-D and nitrogen metabolism. Differential binding of 2,4-D within the cells appears to be the most likely explanation for the differences in response to 2,4-D.

Two Louisiana sugarcane cultivars (interspecific hybrids of the genus Saccharum) CP 52–68 and L 60-25 were sprayed with herbicides commonly used for preemergence and postemergence control of johnsongrass (Sorghum halepense (L.) Pers.) and other weeds. The preemergence weed control treatments of 3-tert-butyl-5-chloro-6-methyluracil (terbacil) at 1.8 kg/ha and (2,3,6-trichlorophenyl)acetic acid (fenac) at 5 kg/ha were compared to a mixture of sodium salt of trichloroacetic acid (TCA) at 11 or 19 kg/ha plus 2-(2,4,5-trichlorophenoxy)propionic acid (silvex) at 3.4 kg/ha (control). Herbicides were applied after planting in the fall, reapplied the following spring (after sugarcane emerged), and applied again in the second spring on the stubble crop (after sugarcane emerged). In the stubble crop the sodium salt of 2,2-dichloropropionic acid (dalapon) at 0, 5, or 10 kg/ha was applied as a postemergence spray over the top of sugarcane. In the factorial arrangement each cultivar received all combinations of the preemergence x postemergence treatments.

Terbacil did not injure either cultivar, but fenac injured both enough to reduce the yield of sugar in plant cane by about 10% as compared to the TCA plus silvex control. Stubble crop yields were not affected by fenac or terbacil. CP 52–68 was more tolerant to dalapon treatments than L 60–25. Both cultivars tolerated dalapon at 5 kg/ha relatively well although the yield of L 60–25 was reduced by about 5%. However at 10 kg/ha, dalapon reduced yields of CP 52–68 and L 60–25 by about 10 and 18%, respectively. Combinations of preemergence and postemergence treatments did not interact to reduce yields more than the combined effects of each treatment.

Seed were harvested from soybean [Glycine max (L.) Merr. ‘Cutler’] plants treated at flowering and pod filling with (2,4-dichlorophenoxy)acetic acid (2,4-D), 4-(2,4-dichlorophenoxy)butyric acid (2,4-DB), and 3,6-dichloro-o-anisic acid (dicamba). Progeny of plants treated at flowering with 2,4-D and 2,4-DB or at pod filling with the lowest rate were normal. When higher rates were applied at pod filling, these phenoxy herbicides caused appreciable injury to the progeny in the form of reduced emergence and dry weight and malformed unifoliate leaves. Dicamba was much more injurious to the progeny of treated plants than 2,4-D and 2,4-DB. Even at low rates dicamba caused reduced germination, emergence, and dry weight and malformed first trifoliate leaves.

Isolated plant cells (Zinnia elegans Jacq. leaf tissue) and protoplasts (immature tomato fruit, Lycopersicon esculentum Mill.) were obtained by hydrolysis of pectic substances in the middle lamella and the primary cell wall, respectively. Both types of cells were stabilized in an inorganic salt solution and used to study absorption and distribution of four 14C-herbicides. Intracellular distribution within the protoplast was determined by ultracentrifugation in a discontinuous Ficoll gradient. Marked absorption of p-nitrophenyl-α,α,α-trifluoro-2-nitro-p-tolyl ether (fluorodifen) and α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) by the isolated cells was observed; absorption increased with time. Trifluralin was retained within the cell more strongly than fluorodifen. Similar absorption patterns of fluorodifen and trifluralin by protoplasts were observed. Trifluralin was incorporated to a greater extent than fluorodifen by the cells and protoplasts. Trifluralin was distributed evenly between the mitochondrial and the chloroplasts-nuclei fractions; whereas fluorodifen was concentrated in the chloroplast-nuclei fraction. No significant absorption of 1,1-dimethyl-3-(α,α,α-trifluoro-m-tolyl)urea fluometuron) or 3-(4-bromo-3-chlorophenyl)-1-methoxy-1-methylurea (chlorbromuron) was detected by either the isolated cells or protoplasts.

Tomato (Lycopersicon esculentum Mill. ‘Campbell 17’) plant height and dry weight of tops decreased with increasing rates of α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) and increased with increasing rates of phosphorus. Trifluralin and phosphorus interacted in their effects on root growth; phosphorus was less effective in promoting root growth as the rate of trifluralin increased. Phosphorus content of plant tops increased with each increment of soil-applied phosphorus at 0 and 0.84 kg/ha of trifluralin, but each increment of applied phosphorus did not significantly increase plant phosphorus content at higher rates of trifluralin. The inhibitory effect of trifluralin on phosphorus uptake diminished with time in 1969. Interactions between trifluralin and phosphorus did not occur in 1970.