The adsorption of dicquat dibromide as affected by available soil moisture and concentration of diquat was studied on Blount silt loam soil in east central Indiana. The diquat under varying concentrations and soil moisture conditions was topically applied to twenty-seven, 1/2 meter square sample plots with the surface vegetation removed to expose bare soil.The soil texture of the research site was determined using the Bouyoucos hydrometer method. From the texture analysis, the highly adsorptive montmorillonite clay was determined to be the major adsorptive surfaces available to the diquat radical. With the montmorillonite clays being the major adsorptive surfaces, it was concluded that the applied diquat was completely adsorbed by the soil colloids.Using a modified Langlois-Stemp-Liska procedure for pesticide extraction and clean-up, the major effect of the herbicide concentrations and the soil moisture conditions on the adsorptive capacity of the soil colloids for the diquat radical was determined to be at the level of degrees of adsorption.Ball State UniversityMuncie, IN 47306

Thesis (Ph.D.)--Mississippi State University. Department of Plant and Soil Sciences. / Title from title screen. Includes bibliographical references.

No description available.

No description available.

No description available.

A leaching study was undertaken with $ sp{14}$C radio-labelled atrazine in long, intact, soil columns to investigate the fate and transport of atrazine in a Quebec sandy loam soil and to test two contaminant transport models, namely PRZM and LEACHMP. / Results indicated a large variation in atrazine concentration. The maximum levels in the leachate of the soil columns ranged from 0 to 11.2 $ mu$g/L. Deisopropyl-atrazine, the principal metabolite in the soil columns, was detected near the soil surface and did not leach beyond 15 cm depth. The adsorptive and desorptive capacity of atrazine in the soil columns was mainly attributed to organic matter and moisture content. / LEACHMP was found to be superior in predicting hydrologic characteristics in the soil columns as compared to PRZM which required calibration. Both models underestimated levels of atrazine near the soil surface and in the leachate (115 cm depth). The results from first and second order analysis for PRZM and LEACHMP showed considerable uncertainty in atrazine fate and transport. First and second order analyses were found to be useful tools in indicating where efforts to reduce uncertainty can best be directed.

No description available.

Field trials were conducted to evaluate the effect of quizalofop-ethyl on quackgrass plants in a potato cropping sequence. Fall and summer applications were compared for their quackgrass control potential. Season-long quackgrass control was obtained with quizalofop-ethyl at 96 g/ha following summer application. An increase in the rate of quizalofop-ethyl did not further improve control. Yields with quizalofop-ethyl at 96 g/ha were similar to standard treatments sethoxydim and fluazifop-butyl at recommended rates. Quackgrass control following a summer application was not maintained through to the following season. Fall applications did not result in adequate control of quackgrass the following season at any of the quizalofop-ethyl rates tested.

This thesis reviews the scientific, litigatory, policy parameters of the Agent Orange controversy. Agent Orange, an herbicide used by the United States during the Viet Nam War, is the subject of continuing conflict involving its possible deleterious effects on veterans who may have been exposed to the herbicide. Central to this controversy are various legal issues. Many of these issues are a result of the governmental philosophy that defines government’s role vis-a-vis citizens, its employees, and the private enterprise sector.This study critically reviews the areas which are of major influence in this subject area and makes a proposal for action involving the legal issue of the burden of proof.

This study addressed the possibility of rice blast fungus (Magnaporthe grisea) as a potential bioherbicide for the control of crabgrass (Digitaria sanguinalis), in turf/lawn plantings. Experiments were: (i) evaluation of the effect of bioherbicide inoculum dosage (titer) on disease severity in crabgrass; (ii) competition between crabgrass and tall fescue (Festuca arundinacea Schreb. 'Fawn') and the additive effect of rice blast bioherbicide on the competitiveness of crabgrass; (iii) survival of rice blast spores under non-conducive infection conditions on crabgrass; and (iv) effect of multiple inoculations of rice blast fungus and subsequent disease on crabgrass.Spore concentrations of 5 x 105 to 1 x 106 conidia/mI had no significant difference in effect on mean biomass reduction of treated crabgrass. All produced tissue death and loss of vigor in treated crabgrass, but no plant death. In one trial, a spore concentration of 2 x 106 conidia/ml produced 100% biomass loss in treated crabgrass.Competition studies indicated crabgrass will out-compete fescue 'Fawn' in plots of equal numbers of each plant, i.e., 3 fescue and 3 crabgrass. In 10 x 10 cm mini-lawns of fescue interspersed with 5 crabgrass plants, fescue will out-compete the crabgrass. In mini-lawns of fescue and crabgrass, infection of crabgrass with non-lethal doses of rice blast fungus improved fescue's ability to out-compete crabgrass. Three methods of investigating competition were tested. Mini-lawns sown with 0.5 g fescue seed (approx. 200 seeds) with crabgrass seed sown into centers of the four quadrants and in center of the mini-lawn, worked best.Survival of Magnaporthe grisea conidia under non-conducive conditions was tested by drying inoculated crabgrass seedlings for 0-48 hours prior to dew-deposition. Treatments verified spores remain viable at least 24 hours on crabgrass leaves under greenhouse conditions (25-40° C and 25-75% relative humidity).Two successive inoculations (at 3 days and 7 days after primary inoculation) of crabgrass with M. grisea conidia (5 x 105 conidia/ml) resulted in significant reduction in growth compared to a single spore application.Results suggested Magnaporthe grisea exhibits potential for future development as a commercial bioherbicide to control crabgrass (Digitaria sanquinalis). Current studies investigated integration in lawn grass, but should be applicable to situations anywhere crabgrass is considered a weed e.g., in corn (Zea mans) or soybeans (Glycine max). / Department of Biology