No description available.

A herbicidial mixture of diquat and endothall used for control of aquatic macrophytes was evaluated to determine the environmental persistence of the combination and its components and phytotoxicity for egeria (Egeria densa). The tests were conducted in wooden pools illuminated with a 15 hr photoperiod with flourescent lights. Diquat was assayed by a spectrophotometric procedure and endothall was quantified using a gas-liquid chromatographic technique, Persistence of diquat in water was decreased by the addition of plants and sediments to the system; whereas the decline of endothall in water was independent of the presence of plants and sediments at the concentrations tested. No measurable differences existed between the persistence of the mixture under lentic and lotic conditions. The presence of each herbicide in the mixture appeared to decrease the uptake in plants and sediments and increase the persistence of the other herbicide in water. Results of testing the mixture and its components individually under various water hardnesses (32 mg/1 to 460 mg/1) indicate the phytotoxicity of the mixture and diquat decreased as water hardness increased, while the phytotoxicity of endothall remained unchanged. Herbicide concentration decline in water appeared independent of water hardness. While diquat was effective in controlling egeria, endothall was not, indicating that the role of the mixture for treating egeria should be reevaluated. / M.S.

Qualitative and microcosm models were used to predict effects of herbicide application for control of Myriophyllum spicatum. Predictions were compared to data from Pat Mayse Lake, a Texas reservoir, where localized areas were treated with endothall. Although milf oil was temporarily eliminated, when endothall was used according to manufacturer's directions, no ecologically significant direct or indirect effects were observed on nontarget species or abiotic water quality. Comparisons of the predictions with field data confirmed the capabilities of this approach for estimating risk and emphasizing the importance of identifying regulating or driving factors that modify environmental impacts of aquatic weed control programs so they can be incorporated into future risk assessments.

Subirrigation systems are generally used in humid areas to provide suitable moisture conditions for plant growth. These systems can also be used to reduce pesticide loadings from agricultural lands, since they tend to keep the discharging waters within farm boundaries for extended periods of time. This allows for greater pesticide microbial and chemical degradation. / A three-year field lysimeter study was initiated to investigate the role of subirrigation systems in reducing the risk of water pollution from the three most commonly used herbicides in Quebec, namely atrazine (2-chloro-4[ethylamino]-6[isopropylamino]-1,3,5-triazine), metribuzin (4-am ino-6(1,1-di meth yl eth yl)-3-(meth yl thio)-1,2,4-tria zin-5(4H)-one), and meto lach lor (2-chlo ro-N-(2-eth yl-6-methyl phen yl)-N-(2-meth oxy-1-meth yl eth yl)acet amide). Eighteen PVC lysimeters, 1 m tall x 0.45 m diameter, were packed with a sandy soil. Three water table management treatments, i.e. two subirrigation treatments with constant water table depths of 0.4 and 0.8 m, respectively, and a free drainage treatment in a completely randomized design with three replicates were used. Grain corn (Zea mays L.) and potatoes (Solanum tuberosum L.) were grown on lysimeters, and herbicides were applied each year at the locally recommended rates at the beginning of each summer. Soil and water samples were collected at different time intervals after each natural or simulated rainfall event. Herbicides were extracted from soil and water samples and were analyzed using Gas Chromatography. / From the three years results (1993--1995), it has been concluded that all three herbicides were quite mobile in this sandy soil, as they leached to the 0.85 m depth below the soil surface quite early in the growing season. This suggests that if the drainage effluent or seeping waters from sandy soils of agricultural lands in southern Quebec drain freely, they may be considered to be a serious non-point source of pollution to the water bodies. The results have also shown that herbicide concentration decreased with soil depth as well as with time, meaning that the higher herbicide residues were found at top layers, and soon after the herbicide application. The herbicide mass balance study revealed that when the drainage effluent was kept within the lysimeters under the subirrigation setup, there was a statistically significant reduction of atrazine and metribuzin residues (shorter half lives) in the adsorbed and liquid phases. However, the reduction in metolachlor concentration under the subirrigation system was not statistically significant. These findings suggest that subirrigation, combined with certain herbicides can significantly reduce the herbicide loadings from corn and potato farms in southwestern Quebec, and become environmentally beneficial. / A computer simulation model (PRZM2), was used to simulate atrazine, metribuzin, and metolachlor leaching in the lysimeters, under subsurface drainage conditions. The simulated values for all three chemicals in most of the cases followed the leaching pattern of observed data. But the model either under- or over-estimated the herbicide concentrations in the soil. This could have been caused by simplistic instantaneous linear adsorption/desorption of herbicides, and inadequacy of conventional Darcian approach for the treatment of matrix flow.

No description available.

Thesis (MScAgric)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: The aim of this study was to determine the effect of a grass herbicide, a broadleaf herbicide with some grass control capabilities, method of tillage (tine and no-tillage) at planting of wheat as well as different medic cultivars on the regeneration, dry matter (OM) production and quality of a medic pasture. The trial was conducted at Langgewens experimental farm in the Swartland wheat producing area. Nine medic cultivars of three different species were evaluated after being sprayed with either haloxyfop-R-methyl (HAL) ester or imazamox (IMI) and subjected to either a tine tillage or a no tillage treatment at planting of wheat. Soil samples were taken during January 2000 to determine the size of the medic and weed seedbank as well as the degree of dormancy in the medic seeds, while OM samples were taken throughout the growing season to determine the OM production of the different medic cultivars and weed species. OM samples taken during October 1998 on the same pasture, were used to determine the crude protein (CP) and neutral detergent fibre (NOF) content of the pasture. The samples were subjected to in vitro digestion and the digestibility of pasture CP (OCP), NOF(ONOF) and DM (DOM)were determined. Results showed that seedling establishment differed between cultivars used, herbicide treatments applied as well as the crop stage in the rotation. The cultivars produced more seedlings where IMI was applied compared to HAL as well as where the area consisted of two year pasture compared to one year pasture (1998) and one year wheat (1999). After a year of pasture and a year of wheat, cultivars Sephi and Paraggio produced the most seedlings, while Caliph and Orion produced the least. Caliph however, showed a very high degree of seed dormancy while Orion's low seedling establishment was due to its sensitivity to the IMI herbicide used. Little difference was found between the nine cultivars early in the season (July - August) with regard to cumulative OM production, except for Orion, whose growth was severely damaged by the IMI treatment. At the end of the growing season (October), the cultivar Caliph's cumulative OM production (2010.1 kg/ha) was significantly higher than all the other cultivars, except for Parabinga (1053. 4 kg/ha). Oifferent pasture samples, of which the botanical composition was known, was analysed for CP, NOF, OOM, OCP and ONOF. There was no significant difference in pasture composition during 1998 but variation in the pasture composition did however cause the IMI treatment, compared to the HAL treatment, to have a lower ONOFand OOMcontent. A modelling procedure was used to predict the pasture quality parameters (CP, NOF, OOM,OCP and ONOF) from the pasture composition (medic hay, medic pods, grassy and broadleaf weeds). This prediction of CP, NOF, OOM, ONOF and OCP from the pasture components had a relative low accuracy (49 -74.1 %) and a further refinement of this model for possible use on farms in order to improve grazing management and animal production is advised. In conclusion it could be said that broadleaf weed control caused a definite increase in medic seed and OMproduction, but Orion should not be used with an IMI herbicide. All the cultivars, except for Orion, produced enough seedlings up to the second year to ensure sustainability of the medic pasture. All the cultivars, except for Orion, produced a sufficient amount of OM early in the growing season. Caliph however, produced by far the most OM later in the growing season. A reduction of broadleaf weeds and medic pods will increase the digestibility of NOFand OMand therefore increase the quality of the pasture. Pods however are an important part of summer forage and the aim should therefore rather be to reduce the number of broadleaf weeds in the pasture. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die effek van 'n gras en breëblaar onkruiddoder (wat sekere grasse beheer), metode van bewerking tydens die saai van koring asook nege verskillende medic kultivars op die regenerasie, droë materiaal produksie en kwaliteit van medic weidings te bepaal. Die proef is gedoen op Langgewens proefplaas wat geleë is in die Swartland koring produserende gebied. Nege medic kultivars is geëvalueer nadat die weiding met of haloxyfop-R-metiel ester (HAL) of imazamox (IMI) onkruiddoders gespuit is en onderwerp is aan of 'n vlak tand of geen bewerking tydens die saai van koring. Grondmonsters is geneem in Januarie 2000 om die grootte van die medic en onkruid saadbank asook om die graad van dormansie in die verskillende medic kultivars se sade te bepaal. Droë materiaal monsters is gedurende die 2000 groeiseisoen geneem om die droë materiaal produksie van die verskillende medic kultivars asook onkruid spesies te bepaal. Droë materiaal monsters is gedurende Oktober 1998 geneem en gebruik om die ruproteïn (CP) en neutraaloplosbare vesel (NDF) inhoud van die weiding te bepaal. Die monsters is in vitro verteer en die verteerbaarheid van CP (OCP), NDF (ONOF) en droë materiaal (DOM) is bepaal. Resultate wys dat saailing vestiging verskil tussen die verskillende kultivars wat gebruik is, verskillende onkruiddoder behandelings asook die stadium van die weidings/koring. Die kultivars het meer geproduseer waar die weiding met IMI behandel is in vergelyking met waar HAL toegedien is, asook waar koring nog nie gesaai is nie. Na 'n jaar van weiding en 'n jaar van koring, het die kultivars Sephi en Paraggio die meeste saailinge, en Caliph en Orion die minste saailinge gehad. Caliph het egter 'n hoë graad van dormansie in sy saad getoon, terwyl die swak vestiging van Orion die gevolg is van die kultivar se hoë sensitiwiteit teenoor IMI. Min verskil is gevind tussen die nege kultivars, vroeg in die groei seisoen (Julie - Augustus), wat kumulatiewe droë materiaal produksie betref, behalwe vir Orion wat erg beskadig is deur die IMI behandeling. Aan die einde van die groeiseisoen (Oktober 2000) was die kumulatiewe droë materiaal produksie van die kultivar Caliph (2010.1 kg/ha) betekenisvol hoër as al die ander kultivars behalwe vir Parabinga (1053.4 kg/ha). Weidingsmonsters, waarvan die botaniese samestelling bekend was, is ontleed vir CP, NDF, DDM, DCP en DNDF. Daar is geen betekenisvolle verskille gevind in die botaniese samestelling van die weidingmonsters geneem in 1998 nie,maar die variasie in botaniese samestelling het veroorsaak dat IMI in vergelyking met HAL 'n laer DNDF and DDM inhoud het. 'n Model is opgestel wat die weidingskomponente (medic hooi, medic peule, gras en breëblaar onkruide) gebruik om die kwaliteits parameters (CP, NDF, DDM, DCP en DNDF) van die weiding te skat. Hierdie skatting van CP, NDF, DDM, DCP en DNDF deur van die weidingskomponente gebruik te maak het 'n relatiewe lae akuraatheid gehad (49 -74.1 %) en verdere verfyning van hierdie model vir moontlike gebruik op plase, ten einde weidings bestuur en diere produksie te verbeter, word voorgestel. Die gevolgtrekking kan gemaak word dat breëblaar onkruidbeheer 'n definitiewe verbetering in die medic saailing en droë materiaal produksie van die medies te weeg gebring het, maar die kultivar Orion behoort nie saam met 'n IMI gebruik te word nie. AI die getoetste kultivars, behalwe Orion, het voldoende saad oorlewing vertoon tot en met die tweede jaar van die rotasie om lewensvatbaarheid van die sisteem te verseker en alle kultivars, behalwe Orion, het voldoende droë materiaal produseer vroeg in die groeiseisoen. Caliph het egter laat in die groeiseisoen by verre die meeste droë materiaal geproduseer. 'n Vermindering in die hoeveelheid breëblaar onkruide en peule in die weiding sal tot 'n verhoging in die verteerbaarheid van NDF en DM lei en dus 'n verhoging in die kwaliteit van die weiding tot gevolg hê. Peule is egter 'n belangrike bron van voedsel aan weidende diere gedurende droë somermaande en die verbetering van weidings moet eerder gedoen word deur te poog om breëblaar onkruide te beheer.

by Tsui Tsz Ki, Martin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 119-138). / Abstracts in English and Chinese. / Acknowledgements --- p.I / Abstract --- p.III / Table of Contents --- p.VII / List of Tables --- p.XII / List of Figures --- p.XIV / Abbreviations --- p.XVI / Chapter Chapter 1 --- General Introduction / Chapter 1.1 --- Research Background --- p.1 / Chapter 1.1.1 --- General description of glyphosate --- p.1 / Chapter 1.1.2 --- Physical and chemical properties of glyphosate --- p.2 / Chapter 1.1.3 --- Commercial formulations based on glyphosate --- p.3 / Chapter 1.1.4 --- Overview of ecotoxicological studies of glyphosate-based formulations --- p.4 / Chapter 1.1.4.1 --- Aquatic toxicity of glyphosate-based formulations --- p.4 / Chapter 1.1.4.2 --- Environmental fate of glyphosate-based formulations in waters --- p.12 / Chapter 1.1.5 --- Interaction of glyphosate and other substances --- p.14 / Chapter 1.2 --- Overview of Aquatic and Sediment Toxicology --- p.16 / Chapter 1.2.1 --- Aquatic toxicology --- p.16 / Chapter 1.2.2 --- Introduction to sediment toxicology --- p.19 / Chapter 1.3 --- "Significance, Outline and Objectives of the Present Study" --- p.20 / Chapter 1.3.1 --- Significance of the research --- p.20 / Chapter 1.3.2 --- Thesis outlines and research objectives --- p.22 / Chapter Chapter 2 --- Aquatic Toxicity of Glyphosate-based Herbicides to Different Organisms and the Effects of Environmental Factors / Chapter 2.1 --- Introduction --- p.25 / Chapter 2.2 --- Materials and Methods --- p.26 / Chapter 2.2.1 --- Test organisms --- p.26 / Chapter 2.2.2 --- Test chemicals --- p.27 / Chapter 2.2.3 --- Comparison between different organisms --- p.27 / Chapter 2.2.4 --- Environmental factors in modifying Roundup® toxicity --- p.30 / Chapter 2.2.5 --- Analysis of glyphosate concentration --- p.31 / Chapter 2.2.6 --- Validity of tests and statistical analyses --- p.32 / Chapter 2.3 --- Results --- p.32 / Chapter 2.3.1 --- Comparison between different groups of organisms --- p.32 / Chapter 2.3.2 --- Environmental factors in modifying Roundup® toxicity to C.dubia --- p.35 / Chapter 2.4 --- Discussion --- p.36 / Chapter 2.4.1 --- Toxicity of glyphosate to photo synthetic organisms --- p.36 / Chapter 2.4.2 --- pH-associated toxicity of glyphosate --- p.37 / Chapter 2.4.3 --- High potency of surfactant --- p.38 / Chapter 2.4.4 --- Effects of environmental factors on Roundup® toxicity --- p.38 / Chapter 2.5 --- Conclusions --- p.39 / Chapter Chapter 3 --- "Toxicity of Rodeo®, Roundup® Biactive and Roundup® to Water-column and Benthic Organisms and the Effect of Organic Carbon on Sediment Toxicity" / Chapter 3.1 --- Introduction --- p.41 / Chapter 3.2 --- Materials and Methods --- p.43 / Chapter 3.2.1 --- Test chemicals --- p.43 / Chapter 3.2.2 --- Test organisms --- p.43 / Chapter 3.2.3 --- Toxicities to water-column and benthic organisms --- p.44 / Chapter 3.2.4 --- Effect of sediment organic carbon --- p.45 / Chapter 3.2.5 --- Statistical analyses --- p.48 / Chapter 3.3 --- Results --- p.48 / Chapter 3.3.1 --- Toxicities to water-column and benthic organisms --- p.48 / Chapter 3.3.2 --- Effect of sediment organic carbon --- p.49 / Chapter 3.4 --- Discussion --- p.54 / Chapter 3.4.1 --- Different sensitivities between water-column and bethic animals --- p.54 / Chapter 3.4.2 --- Relative toxicities of three herbicides --- p.56 / Chapter 3.4.3 --- Route of exposure of herbicides in sediment to organisms --- p.57 / Chapter 3.4.4 --- Sediment toxicity of glyphosate-based formulations --- p.58 / Chapter 3.4.5 --- Effect of organic carbon on partitioning and toxicity --- p.60 / Chapter 3.5 --- Conclusions --- p.61 / Chapter Chapter 4 --- Joint Toxicity of Glyphosate and Several Selected Environmental Pollutants to Ceriodaphnia dubia / Chapter 4.1 --- Introduction --- p.63 / Chapter 4.2 --- Materials and Methods --- p.65 / Chapter 4.2.1 --- Test organisms and toxicity tests --- p.65 / Chapter 4.2.2 --- Test chemicals --- p.66 / Chapter 4.2.3 --- Experiment I: Joint acute toxicity of Roundup® and nine toxicants --- p.66 / Chapter 4.2.4 --- Experiment II： Effect of IPA salt of glyphosate alone at EEC on toxicities of heavy metals --- p.67 / Chapter 4.2.5 --- Basic water properties and chemical analyses --- p.69 / Chapter 4.2.6 --- Statistical analyses --- p.70 / Chapter 4.3 --- Results --- p.70 / Chapter 4.3.1 --- General conditions and recovery for spiked chemicals --- p.70 / Chapter 4.3.2 --- Experiment I: Joint acute toxicity of Roundup® and nine toxicants --- p.71 / Chapter 4.3.3 --- Experiment II: Effect of IPA salt of glyphosate alone at EEC on toxicities of heavy metals --- p.73 / Chapter 4.4 --- Discussion --- p.75 / Chapter 4.4.1 --- Interactions of Roundup® and other toxicants --- p.75 / Chapter 4.4.2 --- Joint toxicity of dissimilar chemicals --- p.77 / Chapter 4.4.3 --- Complexation of glyphosate with metals interactions between liquid/solid phases --- p.79 / Chapter 4.5 --- Conclusions --- p.83 / Chapter Chapter 5 --- Environmental Fate of Glyphosate and its Nontarget Impact: a Case Study in Hong Kong / Chapter 5.1 --- Introduction --- p.85 / Chapter 5.2 --- Materials and Methods --- p.87 / Chapter 5.2.1 --- Description of study sites --- p.87 / Chapter 5.2.2 --- Physicochemical characteristics of different matrices --- p.88 / Chapter 5.2.3 --- Continuous weather monitoring --- p.89 / Chapter 5.2.4 --- Herbicide applications --- p.89 / Chapter 5.2.5 --- Experimental designs --- p.90 / Chapter 5.2.5.1 --- Estuarine enclosure experiment --- p.90 / Chapter 5.2.5.2 --- Freshwater pond experiment --- p.92 / Chapter 5.2.6 --- Schedule of sample collection and sample storage --- p.92 / Chapter 5.2.7 --- Sample preparation --- p.94 / Chapter 5.2.7.1 --- Water samples --- p.94 / Chapter 5.2.7.2 --- Sediment samples --- p.94 / Chapter 5.2.8 --- Sample determination --- p.95 / Chapter 5.2.8.1 --- Pre-column derivatization --- p.95 / Chapter 5.2.8.2 --- High performance liquid chromatography analyses --- p.95 / Chapter 5.2.8.3 --- Calibration of glyphosate and AMPA --- p.95 / Chapter 5.2.8.4 --- Recovery of glyphosate in spiked samples --- p.96 / Chapter 5.2.9 --- Statistical analyses --- p.96 / Chapter 5.3 --- Results --- p.96 / Chapter 5.3.1 --- Site characteristics --- p.96 / Chapter 5.3.2 --- Weather conditions during herbicide application --- p.99 / Chapter 5.3.3 --- Chemical analyses --- p.100 / Chapter 5.3.4 --- In-situ toxicity tests --- p.104 / Chapter 5.4 --- Discussion --- p.106 / Chapter 5.4.1 --- Site-specific factor affecting the environmental fate --- p.106 / Chapter 5.4.1 --- Site-specific factor affecting the environmental fate of glyphosate --- p.106 / Chapter 5.4.2 --- Glyphosate in water and sediment --- p.106 / Chapter 5.4.3 --- Homogeneity of glyphosate in surface water and sediment --- p.109 / Chapter 5.4.4 --- Effect of weather conditions on environmental fate of glyphosate --- p.109 / Chapter 5.4.5 --- Biological impact of Roundup® --- p.110 / Chapter 5.5 --- Conclusions --- p.112 / Chapter Chapter 6 --- General Conclusions --- p.113 / References --- p.119

A variety of conservation trends have gained and lost favor throughout the years in agriculture, with U.S. Farm Bills often influencing what conservation practices are implemented by farming communities throughout the U.S. This dissertation focuses on the unintended consequences of conservation management practices in the Fifteenmile Watershed of Wasco County, Oregon. Specifically, I seek to address how farmer enrollment in various conservation techniques, loosely defined as no-till agriculture, has affected soil and water quality through the increased use of herbicide, and subsequently rendered ecological and human health vulnerable. Using a critical physical geography framework, I address both the biophysical factors and social structures that have co-produced changes in soil and water quality in the study area of this research through intensive physical field data collection, spatial analysis, social surveys, and interviews. I also demonstrate how three neoliberal sets of processes: market-friendly reregulation; state rollback and deregulation; and the creation of self-sufficient individuals and communities, have transformed the human socio-environmental relationship to agriculture. These processes have had significant effects on the policies governing how soil and water quality are managed on both a state and national level, and have created a dependence on enrollment in conservation practices that may ultimately prove counterproductive for long term goals of environmental protection and sustainability.

Although the use of pesticides is necessary to meet the socio-economic needs of many developing countries, especially in Africa, side effects of these bio-active chemicals have contributed to contaminating aquatic and terrestrial ecosystems. Environmental water quality degradation by pesticides interferes with ecosystem health and poses numerous risks to aquatic life. In South Africa, glyphosate-based herbicides are frequently used to control weeds and invading alien plants, but ultimately end up in freshwater ecosystems. However, there are no South African-based environmental water quality management strategies to regulate these bio-active chemicals. Therefore, this study sought to provide a sound scientific background for the environmental water quality management of glyphosate-based herbicides in South Africa, by conducting both laboratory and field investigations. In the laboratory investigations, aquatic ecotoxicological methods were used to evaluate responses of the freshwater aquatic shrimp Caridina nilotica exposed to Roundup® at different biological system scales, and the responses of multiple South African aquatic species exposed to Roundup® through species sensitivity distribution (SSD). In the field investigations, the effect of Kilo Max WSG on the physicochemical and biological conditions of three selected sites in the Swartkops River before and after a spray episode by Working for Water were evaluated through biomonitoring, using the South African Scoring System version 5 (SASS5) as a sampling protocol. Both Roundup® and Kilo Max WSG are glyphosate-based herbicides. All the data were subjected to relevant statistical analyses. Findings of this study revealed that Roundup® elicited responses at different biological system scales in C. nilotica, while SSD estimates were used to derive proposed water quality guidelines for glyphosate-based herbicides in South Africa. The biomonitoring revealed that using glyphosate-based herbicides to control water hyacinth within the Swartkops River had a negligible impact on the physicochemical and biological conditions. Based on these findings, a conceptual framework that can be used for the integrated environmental water quality management of glyphosate-based herbicides in South Africa was developed as part of integrated water resource management (IWRM). The combined data sets contribute to a sound scientific basis for the environmental water quality management of glyphosate-based herbicides in South Africa.