Experiments were conducted to determine adsorption of methanearsonate by soils, soil separates, and reference clay minerals from solutions of disodium methanearsonate (DSMA), effects of soil type and pH on the leaching of surface-applied DSMA, and effects of soil type and added organic matter on the oxidation of the methyl carbon of methanearsonate.

Adsorption of methanearsonate by kaolinite and vermiculite increased with increasing concentration of DSMA in the equilibrium solution. Kaolinite and limonite adsorbed much more methanearsonate than vermiculite and montmorillonite. The clay fraction of Augusta silt loam adsorbed more methanearsonate than did the sand and silt fractions. Adsorption by whole soils was related generally to their clay contents.

Leaching with 20 successive 1-in increments of water removed 52% of surface-applied methanearsonate from Norfolk loamy sand. Rates of movement of DSMA in Norfolk loamy sand did not differ at three pH levels. About one-half of the applied methanearsonate remained in the surface inch of Decatur clay loam and none was leached below 6 in.

Oxidation of the methyl carbon of methanearsonate was associated with oxidation of soil organic matter in each soil. In three of the soils, there was no evidence of microbiological adaptation to methanearsonate. In Norfolk loamy sand, however, increasing decomposition of methanearsonate relative to soil organic matter occurred with time of incubation. Decomposition of added plant material in this soil enhanced the oxidation of methanearsonate.

Narrow bands of activated charcoal sprayed on the soil surface directly over the rows seeded with alfalfa (Medicago sativa L., var. Cayuga) in the field protected the legume from damage by a broadcast application of 2-isopropylamino-4-(3-methoxypropylamino)-6-methylthio-s-triazine (hereafter referred to as G-36393). Charcoal suspended in water and applied at 25 to 50 lb/A, gave adequate protection from 1.5 lb/A G-36393. Higher rates of charcoal, 100 lb/A, were necessary to protect the legume from a 3.0 lb/A application. Charcoal did not protect alfalfa seedlings from 1.5 lb/A 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine).

In field, soil culture, and nutrient culture experiments, 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) increased percent total nitrogen in all species studied, whether resistant, intermediate, or susceptible to 1 lb/A of atrazine. However, nitrogen content per plant was either unaffected or decreased by these atrazine treatments. One lb/A of atrazine increased percent protein and nitrate nitrogen in most species studied. Atrazine susceptibility apparently was related to its effect on percent non-protein and ammonia in the species tested. One lb/A of atrazine had no effect on percent non-protein nitrogen and decreased percent ammonia nitrogen in resistant species but increased both fractions in intermediate and susceptible species. One lb/A of 2-hydroxy-4-ethylamino-6-isopropylamino-s-triazine (hereafter referred to as hydroxyatrazine), a degradation product of atrazine, had no consistent effect on any nitrogen fraction studied.

Rush skeletonweed (Chondrilla juncea L.), a serious agricultural pest in Australia, is increasing in the western United States. Persistence in established areas is encouraged by the resprouting of all portions of the taproot and wind borne achenes. Invasion to new areas is reduced by short achene life, the germination pattern of young seedlings, and the lack of shade tolerance. Fall applied 4-amino-3,5,6-trichloropicolinic acid (picloram) and 2-methoxy-3,6-dichlorobenzoic acid (dicamba) were effective for chemical control of spot infestations.

This work is an endeavor to aid researchers located in remote areas as well as researchers who may have experienced difficulties in the regulation of controlled environment chambers. Descriptions of the maintenance and use of controlled environment chambers contained herein were compiled over an 8-year period of experience with four chambers. Although the physical characteristics of the controlled environment chambers described are dissimilar from many, the causes and remedies of malfunctions are general and typical of those found in many controlled environment chambers. Several protective devices for expensive equipment are described as well as several common malfunctions and their remedies.

Environmental and physical factors influencing the effectiveness of preemergence applications (4 lb/A) of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) were evaluated under field conditions for 10 Hawaiian sugar cane (Saccharum officinarum L.) plantations. Rainfall, soil pH, organic composition, time lapse between field harvest and herbicide application, and maximum temperature had a significant effect on the resultant period of weed control. The data from 295 field tests conducted over a 10-year period then were subjected to multiple regression analysis. The prediction equation derived via these calculations was sufficiently accurate to justify its application to the Hawaiian sugar cane regions. The single most important factor adversely influencing the preemergence activity of diuron was the lapse of time between harvest and application, a factor within the control of the plantation personnel.

Experiments were conducted on black locust (Robinia pseudoacacia L.) to determine the effect of auxin distribution and degradation on the formation of root suckers. Stump sprouting and root suckering occurred when black locust seedlings were decapitated, and the presence of stump sprouts prevented root suckering. The influence of stump sprouts could be replaced by applying indoleacetic acid (IAA) in lanolin paste to the cut surfaces of root stubs. These results provide additional support for an apical dominance theory of suckering. When IAA-2-C14 in lanolin was applied to the cut surfaces of root stubs, autoradiographs showed that C14 activity was concentrated where the majority of root suckers normally would develop. Apparently, IAA accumulated in this region and inhibited root suckering. When the IAA-lanolin paste was removed from the root stubs after inhibiting suckering for a month, vigorous root suckering took place. This indicated the possibility that black locust roots contain an IAA oxidase system. The existence of such a system was demonstrated by dialyzed enzyme preparations extracted from black locust roots which oxidized IAA in a Warburg apparatus.

Spring and fall applications of 10 soil sterilant herbicides were investigated for control of brush and herbaceous vegetation at five locations in Texas. A majority of the herbicides controlled most brush species. However, 5-bromo-3-sec-butyl-6-methyluracil (bromacil), 2-methoxy-4,6-bis(isopropylamino)-5-triazine (prometone), and 4-amino-3,5,6-trichloropicolinic acid (picloram) were most effective at all locations. A mixture of disodium tetraborates, 3-(p-chlorophenyl)-1,1-dimethylurea (monuron) and trichlorobenzoic acid was very effective for at least 20 months at four of the five locations. Most herbicides controlled herbaceous vegetation for 1 year or less. Bromacil controlled herbaceous vegetation for approximately 2 years at most locations.

Both direct and indirect effects of the environment, and the possible role of the crop in modifying the environment of the weeds, are considered. High humidities and high temperatures in general increase susceptibility, and temperature also may have important morphogenetic effects. Low light intensity before, and high intensity after, spraying appear to increase susceptibility. Light also may affect leaf morphogenesis. Soil condition also may affect susceptibility, particularly soil residues of certain herbicides, and crop competition may contribute to weed mortality. The relationship of stage of growth at spraying to susceptibility is also discussed.

The effects of four densities of annual broadleaf weeds and annual grass weeds and an equal combination of the two on the yields of sugar beet (Beta vulgaris L.) roots and tops, percent sucrose and total solids, average diameter of beet roots, and total plot yields were studied during 1964 and 1965. Broadleaf weeds were more competitive than annual grass weeds and the effects of an equal combination were intermediate. Without cultivation, all weed densities reduced the yield of beet roots below the weed-free plots. Twenty broadleaf weeds/sq ft were required to reduce yields when plots were cultivated and weeds were limited to a 10-in band over the beet row. The effects on the yield of beet tops, average root diameter, and total plot yield were similar to the effects on beet root yield. The components of total plot yield are examined. No weed density had a real effect on beet stand, percent total solids, or percent sucrose of the beet roots.

Uptake of phosphorus by red pine (Pinus resinosa Ait.) seedling roots from a medium containing .0015 ppm P32 was stimulated at 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) levels of 5 and 10 ppmw but inhibited at higher levels of 15 and 20 ppmw. Concentrations of simazine between 5 and 20 ppmw resulted in increased translocation of phosphorus from roots to stem and needles with increasing incubation time from 12 to 96 hr. Combinations of simazine at 10 ppmw with P32 at concentrations above 20 ppm resulted in decreased phosphorus uptake for incubation periods less than 72 hr. Phosphorus content of stems was not greatly influenced by simazine treatment or P32 concentration, but phosphorus content of needles was significantly higher in response to simazine.

The metabolism of 3-amino-1,2,4-triazole (amitrole) in bean (Phaseolus vulgaris L., var. Black Valentine) corn (Zea may L., var. Batam Cross), and sugar beet (Beta saccharifera L.) leaves was studied with both C14 and tritium-labeled amitrole. Insignificant amounts of C14 were recovered in the respired CO2 from plants given amitrole-5-C14. The metabolic conversion of amitrole in leaves was exponential and can be expressed by an equation for a first order reaction. The half-time of amitrole in sugar beet, corn, and bean leaves were 18.7, 28.0, and 23.2 hr, respectively. Radioactivity from amitrole-5-C14 was found in extracts or nucleic acids, proteins, and other plant constituents. Largest amounts of radioactivity were recovered as alcohol soluble metabolites. Experiments with (amitrole-H3) and (amitrole-5-C14) showed the position of hydrogen substitution in each alcohol soluble metabolite.

The anatomy of the first internodes of three different lengths of giant foxtail (Setaria faberii Herrm.) was studied in the seedling stage. Epidermis was non-cutinized throughout the entire length. Least cortical breakdown occurred in an area 1 cm below the coleoptilar node, regardless of the length of internode. Endodermis and pericycle were present throughout the internode length, but identity was lost at the coleoptilar node and above. The number of metaxylem and protoxylem elements decreased basipetally from the coleoptilar node. Adventitious root primordia, found in all first internodes, originated from the pericycle. The total number of primordia, at the growth stage studied, appears to be proportional to the length of the internode, with fewer primordia in the 1-cm sections below the coleoptilar node. The implications of root and shoot uptake are discussed in terms of the anatomy of the first internode.

Selective control of red sorrel (Rumex acetosella L.) in Kentucky bluegrass (Poa pratensis L.) seed fields was obtained with 2-methoxy-3,6-dichlorobenzoic acid (dicamba), 7-oxabicyclo(2.2.1)-heptane-2,3-dicarboxylic acid (endothall), 3-amino-2,5-dichlorobenzoic acid (amiben), 2,3,6-trichlorophenylacetic acid (fenac), and 2,3,6-trichlorobenzoic acid (2,3,6-TBA). Kentucky bluegrass seed yields and germination were not significantly reduced by application of any of the herbicides in the fall even though rates higher than necessary for red sorrel control were used. Application of dicamba in the spring at more than 1/2 lb/A reduced Kentucky bluegrass seed yields and germination. Endothall reduced seed yields when applied in the spring at 4 or 5 lb/A.

Residues of 2,3,6-trichlorophenylacetic acid (fenac) and 2,6-dichlorobenzonitrile (dichlobenil) were determined in irrigation water flowing over canal-bottom plots treated with the herbicides prior to the entry of water. Concentrations of fenac and dichlobenil in the first water to flow over the entire treated plots were 8.82 and 8.63 ppm, respectively. The bulk of the residues was transported from the plots in a very short time, and safe levels were reached after 1 hr of water flow. The dichlobenil burden, picked up by water as it flowed over the treated plot, was effectively reduced as the water passed over untreated canal soil downstream.

The herbicide 5-amino-4-chloro-2-phenyl-3(2H)-pyridazinone (pyrazon) was selective for sugar beets (Beta vulgaris L.). In preemergence treatments, sugar beets tolerated pyrazon at rates up to 6 lb/A, but at this level some mortality occurred. On the other hand, some weed species were susceptible to levels as low as 2 lb/A. Between emergence and the cotyledon stage, both beets and weeds were quite susceptible and the phytotoxicity of pyrazon increased with increasing temperature. In the late cotyledon stage, beets were resistant to pyrazon in aqueous suspension and partially susceptible to an oil-water suspension. Beets in the two to four-leaf stage tolerated an oil-water herbicidal combination, while lambsquarters (Chenopodium albium L.) and redroot pigweed (Amaranthus retroflexus L.) remained susceptible up to the six to eight-leaf stage. Rape (Brassica napus L.) was of intermediate susceptibility. In general, preemergence treatments were the most promising but could be replaced by postemergence treatments of pyrazon in an oil-water emulsion.

Astragalus miser Dougl., var. oblongifolius (Rydb.) Cronq. was analyzed for seasonal and physical distribution of its contained poison. Small chickens (Gallus domesticus, Arbor Acre X Vantress hybrids) and cattle (Bos taurus, Hereford) were used as test animals. The poisonous compound was extracted from dried plants with 95% ethanol, evaporated and redissolved in water, then semi-purified by several extractions with chloroform for toxicological studies. The poison was found primarily in the green leaves. The plants were very poisonous until they began drying in August. Once leaves became bleached at senescence, toxicity disappeared. Plants treated with the triethylamine salt of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) and the alkyl amine salts of 2-(2,4,5-trichlorophenoxy)-propionic acid (silvex) were less poisonous to cattle than untreated plants. Acute poisoning in chickens was characterized by depression, accelerated heart action, followed by congestion of lungs, cardiac insufficiency, paralysis, and heart failure. Chronically poisoned birds exhibited the same syndrome but sustained more severe liver damage.

Soil surface applications of crabgrass (Digitaria spp.) herbicides prevented rooting of Bermudagrass (Cynodon dactylon L., var. 328) from the stolon nodes. Inhibition of root development was confined to the areas of the stolon which were in direct contact with dimethyl 2,3,5,6-tetrachloroterephthalate (DCPA). Placement of the herbicides at various soil depths reduced the number of roots developing below the treatment; however, normal root growth occurred above the treated layer. Under field conditions, certain crabgrass herbicides delayed normal rooting of Bermudagrass from nodes for 12 weeks. Established root systems were not appreciably altered by the herbicidal treatments.