Field and greenhouse studies were conducted to determine the influence of soil organic matter on herbicidal activity using four Pocomoke soils with organic matter contents of 4.8, 7.0, 11.9, and 17.0%. In field experiments, control of giant green foxtail [Setaria viridis var. major (Gaud.) Posp.] was greater than 75% from all treatments of 2-chloro-2′,6′-diethyl-N-(methoxymethyl) acetanilide (alachlor), 2-chloro-N-isopropylacetanilide (propachlor), and N,N-diallyl-2-chloroacetamide (CDAA) with no statistical differences between chemicals, rates, or organic matter levels. Control was statistically lower from all 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) treatments except 2.6 kg/ha at 7% organic matter and 4.4 kg/ha at 7 and 17% organic matter. Under greenhouse conditions, giant foxtail (Setaria faberi Hermm.) was used to establish GR50 values on soils or soil mixtures containing 0.8, 1.9, 3.9, 6.4, 11.0, and 18.7% organic matter for the herbicides used in the field study and for 2-chloro-N-(1-methyl-2-propynyl)acetanilide (prynachlor). Generally as organic matter levels increased, the GR50 values for herbicides increased; the rate of GR50 increase varied with herbicides. A ranking of herbicides from most toxic to least toxic is: propachlor>alachlor>prynachlor>CDAA. Atrazine GR50 values varied from a low similar to propachlor at 0.8% organic matter to 20 times greater than propachlor at 17% organic matter.

An application was developed to project UHF electromagnetic fields into soils containing seeds. The unconfined field (2450±20 Mhz) was effective in killing seeds in the soil. At a fixed energy level the toxicity of the field to wheat (Triticum aestivum L.) and radish (Raphanus sativus L.) was constant or slightly increased as the time of exposure was decreased. Thus, the energy requirement for a given level of toxicity can be met by substituting increased power levels for time of exposure in the range of 100 and 1200 watts.

Trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) required more thorough soil incorporation with a disk, probably to prevent loss by volatility, than did 4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline (nitralin). Mechanical incorporation of nitralin could be delayed for 96 hr after application, whereas trifluralin needed to be incorporated within 24 hr to control weeds. Gas chromatographic analyses of soil showed that trifluralin decreased rapidly during the first 24 hr that incorporation was delayed. Application of trifluralin with undiluted crop oil on dry soil did not prolong the persistence prior to incorporation compared to applications with water.

Monosodium methanearsonate (MSMA) and arsenic acid (AA) were measured simultaneously in johnsongrass (Sorghum halepense (L.) Pers.) and cottonseed (Gossypium hirsutum L. ‘SJ-1’) by a bicolorimetric method. Tissues from plants sprayed with MSMA while growing and tissues with MSMA and AA added just prior to extraction were analyzed. Johnsongrass sprayed with MSMA solution at 11.2 kg/ha contained, on a dry weight basis, 423.0 ppmw of MSMA and 0.00 ppmw of AA at 7 days and 10.83 and 0.21 ppmw, respectively, after 54 days of regrowth. The cotton plants were sprayed twice to runoff with MSMA, first with 0.3 g/L and second with 1.2 g/L. Cottonseed from the sprayed cotton plants contained, on a dry weight basis, 2.45 ppmw of MSMA and 0.08 ppmw of AA after the first picking and 3.02 and 0.10 ppmw, respectively, after the second. Background levels of MSMA and AA were, respectively, on a dry weight basis, 0.63 and 0.02 ppmw in johnsongrass and 0.58 and 0.00 ppmw in cottonseed.

The amount of lipid present on leaves of Canada thistle (Cirsium arvense (L.) Scop.) varied due to ecotype, site where grown, and date of sampling. Thistles from a site with the greatest wind movement and greatest evaporation produced the most lipid per unit area of leaf. The relative lipid yield of ecotypes was similar at different locations. Deposition of lipid on the leaves of Canada thistle increased from the early bud stage to the first bloom and late bloom stages of growth. The amount of lipid on the leaves and previous data on the response of these ecotypes to (2,4-dichlorophenoxy) acetic acid (2,4-D) were highly correlated. Three ecotypes with the most lipid were most resistant and four ecotypes with the least lipid were most susceptible to 2,4-D spray. Two ecotypes were inconsistent in that comparison.

Growth response of five species of soil algae to 4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5 (4H)one (metribuzin) and its 6-isopropyl and 6-cyclohexyl analogs were studied in vitro. Species of Chlorella, Chlorococcum, Chlamydomonas, and Anabaena were exposed to 0.05, 0.1, 0.5, and 1.0 ppm (w/v) of the herbicides in liquid nutrient, while a species of Schizothrix was studied at the same levels in soil culture. With one exception, the growth and numbers of all of the algae were significantly reduced by increasing herbicide concentrations. Anabaena was not affected by 0.05 ppm of the cyclohexyl analog. No growth was permitted by any of the herbicides at 1.0 ppm. Chlorella and Chlamydomonas could not grow in the presence of 0.5 ppm of metribuzin or the cyclohexyl analog. Differences in response to the triazinones were noted between species. Chlamydomonas was the most sensitive and Anabaena and Chlorella the most resistant.

Systems of weed control composed of (a) herbicides only, (b) herbicides plus cultivation, or (c) cultivation only were devised. The most effective systems, involving herbicide sequences plus one “non-dirting” layby cultivation, controlled twelve troublesome species of weeds with acceptable yields of peanuts (Arachis hypogaea L.). On Greenville sandy clay loam, a particularly effective and economical system of weed control consisted of (a) N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine (benefin) used as a preplanting incorporated treatment, then (b) S-propyl dipropylthiocarbamate (vernolate) either incorporated into the soil before planting or injected at planting, and finally, (c) a layby cultivation 5 to 6 weeks after planting. A similarly effective system on Tifton loamy sand involved vernolate injected at planting, 2-sec-butyl-4,6-dinitrophenol (dinoseb) at “cracking”, and 4-(2,4-dichlorophenoxy)butyric acid (2,4-DB) as a postemergence treatment followed by the layby cultivation. The “non-dirting” layby cultivation, averaged over both years and herbicide sequences, significantly increased yields of peanuts on both soil types. None of the systems of weed control caused consistent differences in market grade, average weight per seed, germination, or organoleptic quality of the peanuts.

Roots of susceptible cucumber (Cucumis sativus L. ‘Chicago pickling’) and tolerant wheat (Triticum aestivum L. ‘Manitou’) seedlings were treated with 3,6-dichloro-o-anisic acid (dicamba) or (2,4-dichlorophenoxy)acetic acid (2,4-D) for either 10 or 46 hr. The roots were excised and nucleohistones were isolated and fractionated by polyacrylamide gel electrophoresis. In untreated cucumber roots there were four major nucleohistone fractions. Two of these fractions decreased or were not detectable 10 or 46 hr after treatment with dicamba or 2,4-D. In wheat, the nucleohistone fractions of the treated roots were similar to those of the controls. This suggests that in cucumber more of the DNA template is available for transcription. This suggestion was supported by the fact that the incorporation of 14C-adenine into RNA in cucumber roots 10 hr after treatment with dicamba was increased by 50%, whereas in wheat there was no difference. Furthermore, the incorporation of 14C-leucine into protein in cucumber roots 10 hr after treatment with dicamba was inhibited by 70%, indicating that the increased RNA produced was incapable of translating for protein synthesis. It is proposed that selective phytotoxicity of auxin-like herbicides is based on a differential alteration of RNA species and interference with protein synthesis.

Movement of 2-chloro-N-isopropylacetanilide (propachlor) from a granule to the soil was classified as horizontal, below the granule, above the granule, and into an area within a 3-ppmw contour. The influence of depth of placement, moisture content, temperature, relative humidity, and exposure time on each of the movement classifications was determined. Horizontal movement increased as the temperature, moisture, and exposure time increased. Propachlor tends to move down into the soil under dry conditions and up when the soil is moist. The size of the soil area that contained 3 ppmw was greater for granules placed in the soil than for granules placed on the surface. The size of the area increased as the moisture increased.

Interspecific crosses were made between perennial sowthistle (Sonchus arvensis L.) and annual sowthistle (Sonchus oleraceus L.). Flower head size, leaf type, and creeping root growth of the hybrid were intermediate to those same morphological characteristics of the parents. Backcrosses to the parents produced plants which resembled annual or perennial sowthistle more closely than did the F1 hybrids. Annual sowthistle and backcrosses to annual sowthistle were more tolerant to (2,4-dichlorophenoxy)acetic acid (2,4-D) and 3,6-dichloro-o-anisic acid (dicamba) than were perennial sowthistle or backcrosses to perennial sowthistle. However, annual and perennial sowthistle were similar to each other in response to 4-amino-3,5,6-trichloropicolinic acid (picloram). Natural crosses between annual and perennial sowthistles may account for some of the variability in herbicide response found in perennial sowthistle.

Injury to corn (Zea mays L.) from S-ethyl diisobutylthiocarbamate (butylate) was investigated with respect to hybrid. Field experiments in 1971 at Dillon and Clemson, South Carolina, established that the corn hybrid ‘Coker 71’ was more tolerant to butylate than ‘Pioneer 511A’. Also established as being tolerant and sensitive to butylate were the hybrids ‘Pioneer 3030’ and ‘PAG 644’, respectively. Laboratory studies with 14C-butylate showed that the resistant hybrid ‘Pioneer 3030’ took up less 14C-butylate and metabolized more to 14CO2 than did ‘PAG 644’.

The evapotranspiration of six dominant emersed and floating weeds was studied. Evapotranspiration of water-chestnut (Trapa natans L. var. bispinosa Roxb.), waterlettuce (Pistia stratiotes L.), and swamp morningglory (Ipomea aquatica Forsk.) did not increase water losses significantly. Evapotranspiration of waterhyacinth (Eichornia crassipes (Mart) Solms.) was 30 to 40% higher, that of narrowleaf cattail (Typha augustifolia L.) was 60 to 70% higher, and that of purple nutsedge (Cyperus rotundus L.) was 130 to 150% higher than evaporation from a free water surface under equivalent conditions. Positive correlations (significant at the 1% level) were found between some meterological factors (daily maximum air temperature and daily average wind velocity), evaporation from free water surface, and evapotranspiration from aquatic plants studied.

The persistence of 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) residues under greenhouse conditions was affected by levels of activated carbon added to a silica sand potting medium and by up to four consecutive crops of corn (Zea mays L.). Degradation of atrazine within the sand and removal by the corn crops were both reduced by activated carbon. Atrazine removal by successive crops of corn reduced injury to oat seedlings grown on the sand alone, and absorption by 1.2 g of carbon per kilogram of sand prevented oat injury both with and without cropping. Although 0.4 g/kg of activated carbon inhibited atrazine removal by corn, oat seedlings were not protected from the residues remaining. When exposed to alternate freezing and thawing, the ability of 0.4 g/kg of activated carbon to deactivate atrazine was reduced causing increased oat injury.

The physiological basis for tolerance and susceptibility of four lines of cucumber (Cucumis sativus L.) to the methyl ester of 3-amino-2,5-dichlorobenzoic acid (chloramben) was investigated. ‘MSU 3207’ and ‘MSU 0612’ were tolerant (T), whereas ‘MSU 3159’ and ‘MSU 0866’ were susceptible (S). Intraspecific variability was related to higher concentrations of chloramben in the roots of the susceptible lines, resulting from metabolic differences in these lines and rapid absorption of the herbicide by the roots of ‘S-MSU 3159’. Tolerance of ‘T-MSU 3207’ resulted primarily from low uptake and reduced translocation of the herbicide, while tolerance of ‘T-MSU 0612’ was related to, but not necessarily explained by, a peculiar 14C-label distribution pattern in the leaves. Thin-layer chromatographic analysis of methanol-soluble extracts from the lines studied 3 days after 14C-chloramben methyl ester treatment separated six 14C-metabolites in the roots and five in the shoots. After a 4-hr treatment, 14C-chloramben methyl ester was absorbed and translocated more rapidly than 14C-chloramben by all four lines. Tolerance or susceptibility did not always correlate with the total concentration of radioactivity in methanol-soluble shoot and root extracts.

Bromacil (5-bromo-3-sec-butyl-6-methyluracil) had no effect on germination but reduced growth of emerging shoots of orchardgrass (Dactylis glomerata L. ‘Virginia Common’) more than Kentucky bluegrass (Poa pratense L. ‘Merion’). Fresh weight gain and transpiration were reduced in orchardgrass seedlings at 0.125 ppmw of bromacil whereas 1.0 ppmw were required for reductions in bluegrass. Photosynthesis was inhibited in both plants; however, bluegrass recovered in 6 days. Water soluble carbohydrate content was greater and was not reduced as much by bromacil in bluegrass compared with orchardgrass. Absorption of 2-14C-bromacil from solution and translocation to shoots was directly related to transpiration rate. Bromacil was translocated acropetally from sheath and foliar treatments. Higher metabolic conversion of 2-14C-bromacil occurred in bluegrass compared to orchardgrass. Metabolites detected in plant extracts were 5-bromo-3-(2-hydroxy-1-methylpropyl)-6-methyluracil and an unknown. Traces of 3-sec-butyl-6-methyluracil and 5-bromo-3-sec-butyl-6-hydroxymethyluracil were also detected. Bluegrass tolerance involved high carbohydrate levels in tissues, hydroxylation of bromacil, and recovery of photosynthesis.

Four field studies and two growth-chamber studies were used to evaluate the compatibility of 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) in suspension fertilizer on corn (Zea mays L. ‘Pioneer 321’). Crop yields and tissue analyses were used to determine effects of atrazine on fertilizer availability. Visual and pictorial comparisons determined effects of fertilizer on atrazine phytotoxicity. Fertilizer-herbicide combinations compounded 230 days or sooner before application produced no change in atrazine phytotoxicity or fertilizer availability in growth chamber studies. Preplant-incorporated treatments displayed better fertilizer availability than preemergence treatments in the field. Preemergence treatments resulted in greater atrazine phytotoxicity under drought conditions. No problems of physical compatibility were encountered with the mixtures.

Additions of surfactants to the isooctyl ester of (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T) and the dimethylamine of 3,6-dichloro-o-anisic acid (dicamba) generally did not increase absorption or translocation of the herbicides when they were applied to foliage of five hardwood species and loblolly pine (Pinus taeda L.). Adjusting pH of the formulations to 3, 6, or 9 with a buffering solution had small and inconsistent effects upon absorption and translocation.

Investigations of the behavior of 3-isopropyl-1H-2,1,3-benzothiadiazin-(4)3H-one 2,2-dioxide (bentazon) in water solutions have shown that it was anionic in neutral solutions by exhibiting a strong movement toward the anode in an electrical field. The herbicide was not adsorbed by any of twelve selected Illinois soils or by the cation exchange resin, carboxymethylcellulose (CMC), but was almost completely adsorbed by charcoal and by the anion exchanger, diethylaminoethylcellulose (DEAE). Bentazon moved with the water front on soil thin-layer plates as well as through soil columns.

A 6-year study was conducted to compare the influence of 1,1′-dimethyl-4,4′-bipyridinium ion (paraquat), a mixture of paraquat and 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine), frequent mowing, hay mulch, and cultivation on growth, yield, and nutrition of peach (Prunus persica (L.) Batsch ‘Jerseyland’) trees. The growth and yield of trees which received two annual applications of paraquat or one application of paraquat plus simazine were comparable to those of trees maintained under cultivation or hay mulch. Hay mulched and cultivated trees responded comparably. Hay mulched trees had higher leaf potassium (K) and lower leaf magnesium (Mg) than the other trees. Where grass was controlled only by mowing, trees were generally lower in nitrogen (N), made less growth, and produced less fruit.

Seasonal variation in flowering of common dandelion (Taraxacum officinale Weber) was studied in 1969 and 1970 at Bowling Green, Kentucky. At this location the dandelion flowered throughout the year. Maximum flowering occurred during April and a secondary peak occurred in September and October. Number of flower stems per square meter was not significantly correlated with precipitation, temperature, or day length. Length of stem was positively correlated with temperature and day length. The plants exhibited diurnal variation in flowering habit. Number of times (or days) the heads opened and closed, length of time in which the heads remained open each day, and length of time heads remained closed before opening into mature heads (white balls) varied with time of year.