The type of growth chamber environmental regime used altered the response of sugarbeets (Beta vulgaris L. ‘USH-9′) to desmedipham [ethyl m-hydroxycarbanilate carbanilate(ester)]. No difference occurred in growth retardation following treatment at different times of day when standard growth chamber constant day/night temperature and light cycles were used. When temperatures were programmed and light intensity varied during the day/night cycles, approximating out-of-doors daily cyclic conditions, the herbicide caused greater injury following morning treatments and less injury following late afternoon treatments. Data obtained in the growth chamber under the typical constant day/night pattern did not agree with field derived information; data obtained using the programmed temperature and varying light regime agreed well with field data and with known action of desmedipham. Plants stressed for moisture after treatment were less retarded than plants turgid at treatment; but both showed relationships to time of day at treatment similar to those noted above. Moisture stress prior to treatment diminished growth retardation by desmedipham, and reversed the treatment time of day effect.

Nutrient-solution-grown pepper (Capsicum frutescens L. ‘Early Calwonder’) absorbed 62% of the diphenamid (N,N-dimethyl-2-2-diphenylacetamide) supplied via the roots for 48 h, and 74% in 150 h. Extensive translocation accompanied absorption, and 70 ± 3% of the absorbed 14C was present in shoots of plants harvested after 24- to 150-h treatments. Diphenamid was metabolized rapidly to chloroform-soluble and water-soluble compounds, and to unextracted residues. Chloroform-soluble compounds persisted for 150 h and accounted for more than 50% of the 14C in leaves. Water-soluble compounds other than N-hydroxymethyl-β-D-glycosides accounted for 25% of the water-soluble metabolites in leaves of nonfumigated plants. Ozone fumigation did not affect diphenamid absorption or translocation significantly. In leaves, ozone-enhanced accumulation of water-soluble metabolites more polar than N-hydroxymethyl-N-methyl-2,2-diphenylacetamide-β-D-glucoside (MDAG) and unextracted residues was observed. Ozone fumigation reduced the accumulation of these 14C-fractions in roots.

The 14C-labeled herbicide, Sandoz 6706 [4-chloro-5-(dimethyl-amino)-2-α,α,α-trifluoro-m-tolyl-3(2H)-pyridazinone], was applied to soybean [Glycine max (L.) Merr. ‘Kent’] and sicklepod (Cassia obtusifolia L.) to evaluate differential species response in uptake and translocation. Liquid scintillation spectrometry and radioautographs indicated that in both species 6706 uptake was proportional to its concentration in the cultural solution and to transpiration, provided transpiration and the uptake mechanism were not limited. Translocation of the herbicide from roots to foliage followed the apoplastic route in both plants. A higher concentration of the herbicide accumulated in the upper leaves and apical meristem in sicklpod than in soybean.

Yields of cotton (Gossypium hirsutum L. ‘Stoneville 213′) did not differ with various cultivation practices on two soils in Alabama over a 3 to 5-yr period. Cultivation treatments resulted in cotton yields equivalent to but not greater than those resulting from weed removal without soil stirring. However, lack of any weed control resulted in more than 90% yield reduction on Decatur clay loam soil based on a 5-yr average and 95% yield reduction on Hartsells fine sandy loam soil, based on a 3-yr average.

Dormant (fresh) and nondormant (afterripened) prickly sida (Sida spinosa L.) seeds were extracted and bioassayed for both inhibitory and promotory growth regulators. Both dormant and nondormant prickly sida seeds contained water-soluble inhibitors, but these inhibitor levels in nondormant seeds did not change after 8 hr of incubation. A basic inhibitor was present in dormant seeds, but not in nondormant seeds. Exogenous growth regulators stimulated germination of dormant seeds only when a portion of the seed coat was removed. Promoter levels in nonincubated, dormant and nondormant seeds were similar, but there were increases in promoter levels in nondormant seeds after 8 hr of incubation. However, it was not determined whether the promoter increases were a cause or a result of germination.

The absorption and translocation of 14C-terbutryn [2-(tert-butylamino)-4-(ethylamino)-6-(methylthio)-s-triazine] and 14C-fluometuron [1,1-dimethyl-3-(α,α,α,-trifluoro-m-tolyl) urea] in cotton (Gossypium hirsutum L. ‘SJ-1′) and snapbean (Phaseolus vulgaris L. ‘Tenderette’) were studied. 14C-terbutryn supplied to the roots accumulated in the root system of both species. However, snapbean plants (sensitive) absorbed and translocated more 14C to the shoots than cotton (tolerant), followed by rapid distribution in the leaf mesophyll tissue. In cotton, the translocated 14C-terbutryn accumulated in stems, petioles, and leaf veins. Excised cotton roots absorbed more 14C-terbutryn than excised snapbean roots. The uptake and distribution pattern of root-applied 14C-fluometuron was similar in both species. Foliar application to the primary leaf of snapbeans and to one cotyledon of cotton resulted in 2% of 14C-terbutryn transported acropetally to younger leaves with no basipetal movement. Translocation of 14C-fluometuron from the site of foliar application was two or three times faster than terbutryn with significant basipetal transport in both species.

Products volatilized from arsenical-treated soil were identified and their rates of formation measured to determine if generation of alkylarsines by soils is part of a natural arsenic cycle. 74As-sodium arsenate, 14C-MSMA (monosodium methanearsonate), or 14C-cacodylic acid (hydroxydimethylarsine oxide), were added at 13.3 μMoles (10 ppmw As) to individual flasks containing 100 g of Mattapeake silt loam. Either air or N2 was used to sweep gases from the flasks and through trapping solutions. Arsenical content in the solutions was monitored by liquid scintillation and assayed for arsenic by atomic absorption spectroscopy. Volatile arsine gases were produced under all conditions. The organo-arsenicals formed volatile compounds most quickly under aerobic conditions. In 160 days, the trapping solutions contained 18.0%, 12.5%, and 1.0% of the activity from soils treated with cacodylic acid, MSMA, or sodium arsenate respectively, when flushed continuously with air, and 7.8%, 0.8%, and 1.8% when flushed with N2. The volatile gases were identified as dimethyl- and trimethylarsine (DMA and TMA) by ion exchange and gas chromatography, and mass spectroscopy. Methylarsine (MA) was not detected. Most of the extractable arsenic remaining in the soil was present as a trimethyl arsenical compound regardless of the treatment. Since arsenic was transferred to air regardless of arsenical treatment, the transfer of arsenic from soil to air is part of the natural arsenic cycle in soils.

Metabolites of diphenamid (N,N-dimethyl-2,2-diphenyl-acetamide) were purified from extracts of pepper plants (Capsicum frutescens L. ‘Early Calwonder’) treated via nutrient solution with the herbicide or several of its analogs. The major metabolites were characterized. Diphenamid was metabolized partially via a previously unreported pathway to N,N-dimethyl-2-phenyl-2-[(hydroxyphenyl)-β-0-D-glucosyl] acetamide and its monomethyl analog, and to N-hydroxymethyl glycosides previously reported in other species. Ozone fumigation stimulated the production of both types of glycoside-conjugates. Leaves of plants that had been treated with 30 μM diphenamid and fumigated with ozone for 146 to 149 h contained 304 and 560 nmoles per gram of fresh weight of the hydroxyphenyl and N-hydroxymethyl conjugates, respectively.

Field experiments were conducted to study the feasibility of applying glyphosate [N-(phosphonomethyl)glycine] postemergence for the control of johnsongrass [Sorghum halepense (L.) Pers.], redroot pigweed (Amaranthus retroflexus L.), and hemp sesbania [Sesbania exaltata (Raf.) Cory] in soybeans [Glycine max (L.) Merr.]. Herbicide sprays were directed across the row to weeds growing taller than soybeans in June, July, and August. Herbicide not sprayed on weeds was trapped and reused. Glyphosate at 1.12 and 1.68 kg/ha effectively controlled johnsongrass with little soybean injury and with greatly increased soybean yields. The use of 0.1% surfactant frequently increased the toxicity of glyphosate at 1.12 and 1.68 kg/ha to soybeans, but this adverse effect was overcome by the use of 0.1% anti-drift polymer in sprays. Control of redroot pigweed with glyphosate at 1.12 kg/ha was improved by the use of 0.1% surfactant, but surfactant did not increase control with glyphosate at 1.68 kg/ha. Glyphosate at 1.68 kg/ha, with 0.1% surfactant, was required to provide more than 80% control of hemp sesbania. Glyphosate applied at 1.12 kg/ha in the recirculating sprayer provided equal johnsongrass control, increased soybean yields and caused less soybean injury than when glyphosate at 0.56 kg/ha was applied over-the-top in water or in foam.

The effects of ethephon (2,chloroethyl-phosphonic acid), ancymidol [α-cyclopropyl-α-(4-methoxyphenyl)-4-pyrimidinemethanol], DPX1840 [3,3a-dihydro-2-(p-methoxyphenyl)-8H-pyrazolo(5,1-a)isoindol-8-one], Uni-P293 (2,3-dihydro-5-6-diphenyl-1,4-oxathiin), and morphactins and their interaction with GA (gibberellic acid) on the translocation of 2,4,5-T (2,4,5-trichlorophenoxacetic acid) in bean (Phaseolus vulgaris L. ‘Stringless Green-Pod’) seedlings were determined. The growth retardants and GA were either applied as foliar treatments or injected at the cotyledonary node with 2,4,5-T. Foliar pretreatment of bean seedlings with ethephon and ancymidol 2 days before 2,4,5-T treatment inhibited 2,4,5-T translocation to young shoots but did not affect basipetal translocation greatly. These effects were reversed by foliar application of GA 1 day before 2,4,5-T injection. Foliar pretreatment of bean seedlings with DPX 1840 2 days before 2,4,5-T treatment increased 2,4,5-T translocation to young shoots and inhibited basipetal translocation. The effects of DPX1840 were not reversed by GA treatment. When ancymidol, DPX 1840, and morphactins were injected into the stem tissue with 2,4,5-T the acropetal translocation of 2,4,5-T increased and basipetal translocation was decreased by DPX1840 and morphactins. These effects were not reversed by the simultaneous GA injection. Uni-P293 had little effect on 2,4,5-T translocation. Growth retardants other than Uni-P293 appear to inhibit basipetal 2,4,5-T translocation directly. Ethephon and ancymidol may have secondary effects on 2,4,5-T translocation that can be reversed by GA treatment.

Foliar application of 2.8 μg/plant of glyphosate [N-(phosphonomethyl)glycine] to greenhouse grown sorghum [Sorghum bicolor (L.) Moench ‘Tophand’] seedlings resulted in increased fresh weight. As glyphosate levels were increased to 11.2 μg/plant, diameter of the basal growth zone increased while fresh weight decreased. In growth chamber studies with sorghum and wheat [Triticum aestivum (L.) ‘Era’] seedlings, glyphosate caused the greatest reduction in fresh weight at the optimum growth temperatures for both species. Glyphosate inhibited normal production of basal buds in wheat at the optimum growth temperature and stimulated bud production at temperatures above the optimum. Under normal growth conditions, basal buds in sorghum do not develop; however, application of glyphosate stimulated basal bud development under normal and above-normal temperature conditions. Histochemical analysis of malate dehydrogenase activity in apical meristem tissue of treated sorghum seedlings indicated that growth of the apex was normal and viable.

We have come together to discuss the way in which weeds and water work together to influence yields in agriculture. In the small allotment of time available to us this morning a review of basic knowledge about this relationship would be so general that it could help no one. I believe it would be more appropriate, and more helpful for a group so large, if I tell you of some of the hard realities which come to bear on food production across the world because of this relationship of weeds with moisture. These stories will have to do with such practical matters as the expansion of the world's most important crop, and the difference between good and bad crops on the two sides of the same river under identical climatic conditions in Middle Asia.

The concentrations of 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid] in four species of vegetation varied from 11 to 115 ppmw immediately after application at 2.24 kg/ha but were less than 0.5 ppmw after 1 yr. The 2,4,5-T level in forest floor declined 90% during the first 6 months after application and less than 0.02 kg/ha remained after 1 yr. There was little leaching of 2,4,5-T from the forest floor into soil and no residues were found deeper than 15 cm. Maximum soil residues did not exceed 0.1 ppmw. Residue levels and dissipation rates of 2,4,5-T were similar after one and two successive annual applications.

A water-soluble linseed oil formulation was compared with emulsifiable linseed oil as an additive to bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-(4)3H-one 2,2-dioxide] for redroot pigweed (Amaranthus retroflexus L.) control. A water-soluble linseed oil formulation as an additive to bentazon controlled redroot pigweed better than did an emulsifiable linseed oil additive. Further, the water-soluble linseed oil additive enhanced redroot pigweed control with bentazon more than the emulsifiable linseed oil when a simulated rainfall followed application, or when humidity was low (30 to 45%) or spray volume high (170 to 340 L/ha). Redroot pigweed control with bentazon plus the water-soluble linseed oil additive followed by simulated rainfall in 4 h was similar to control with bentazon applied alone without a simulated rainfall.

Burley tobacco (Nicotiana tabacum L. ‘Kentucky 14′) was grown as a no-tillage crop in 1974 and 1975 by planting tobacco directly into an existing stand of orchardgrass (Dactylis glomerata L.) or rye (Secale cereale L.). Paraquat (1,1′-dimethyl-4,4′bipyridium ion) and glyphosate [N-(phosphonomethyl)glycine] were used to kill existing vegetation. Benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine), oryzalin (3,5-dinitro-N4,N4-dipropylsulfaniiamide), metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)one], and chlorbromuron [3-(4-bromo-3-chlorophenyl), 1-methoxy-1-methylurea] were used to control annual grasses and broadleaf weeds.

Glyphosate was generally more effective than paraquat in killing existing vegetation. There was some injury to the tobacco associated with the glyphosate and paraquat treatments, but this was generally confined to those plants which came into contact with the treated herbage. Metribuzin caused severe damage to the tobacco and was discontinued after the first year. Chlorbromuron caused little injury if kept on the surface but injured the tobacco if incorporated by cultivation as in conventional tillage. Benefin and oryzalin caused little or no injury to the tobacco. All four herbicides gave adequate control of annual grasses and broadleaf weeds.

Putting green turf containing perennial ryegrass (Lolium perenne L. ‘Medalist IV’) overseeded on a bermudagrass [Cynodon dactylon (L.) Pers. ‘Tifway’] was treated with single and sequential herbicide treatments during the spring and transition period from cool to warm season grass. Oxadiazon [2-tert-butyl-4-(2,4-dichloro-5-isopropoxyphenyl)-Δ2-1,3,4-oxadiazolin-5-one] at 2.2 or 4.4 kg/ha and butralin [4-(1,1-dimethylethyl)-N-(1-methylpropyl)-2,6-dinitrobenzenamine] at 3.4 or 6.7 kg/ha reduced the quality of putting green turf immediately after treatment in early spring. Turf injury was greater with oxadiazon than with butralin. Two applications of MSMA (monosodium methanearsonate) at 2.2 or 3.4 kg/ha resulted in a lower quality turf with less ryegrass when compared with the untreated check. Methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] at 1.1 kg/ha severely injured ryegrass and resulted in a lower turf quality.

The movement of biologically active levels of bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-(4) 3H-one 2,2-dioxide] was followed by monitoring photosynthetic activity of plant parts after application of the herbicide. Bentazon was applied to roots, stems, petioles, portions of the canopy, and portions of individual leaves of 4- to 24-day-old common cocklebur (Xanthium pensylvanicum Wallr.) at rates comparable to field application rates. Application of bentazon anywhere on the plant either slowed or stopped photosynthesis in leaves acropetal to the point of application. Contact of bentazon with stems, petioles or roots contributed to the phytotoxicity of the herbicide.

The uptake of naptalam (N-1-naphthylphthalamic acid) by wheat (Triticum vulgare L. ‘Mericopa’) and soybean (Glycine max (L.) Merr. ‘York’) was enhanced when the herbicide was applied simultaneously with SADH (succinic acid-2,2-dimethylhydrazide). Both root and shoot systems of growth regulator-treated plants exhibited enhanced herbicide uptake. Naptalam uptake by wheat seedlings was also stimulated by GA (gibberellic acid), but the GA influence in this respect was less dramatic than that of SADH. The uptake of the herbicide by soybean was not influenced by GA.

The persistence of 2,4-D [(2,4-dichlorophenoxy) acetic acid] and 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid] was studied in the chaparral environment. Chamise (Adenostoma fasciculatum H. & A.), grass and forbs, soil surface litter, and soil were sampled for up to 360 days after herbicide (4.5 kg/ha) application. Over 50% of the 2,4-D and 2,4,5-T recovered was found on soil surface litter while 18 to 31% was found on vegetation. Much less herbicide (0.1 to 0.2%) was found in soil (0 to 5 cm) than in foliage or litter. No herbicide residues were found below the 0 to 5 cm soil sample zone. Herbicide residues on foliage and litter decreased rapidly (up to 93%) within 30 days after application but remained constant thereafter until winter rainfall began. Residues of both herbicides were evident in chamise foliage (0.01 to 0.02%), surface litter (0.01 to 0.03%), and soil (0.01%) up to 360 days after application.

A washer was designed and tested for washing soil from weed seed buried in fabric packets and for separating weed seed from soil. The washer was constructed from inexpensive, readily available materials and was found to function efficiently.