No description available.

The effect of field margin management on crop yield and weed biomass in the crop edge (headland) was investigated. Treatment did not have any significant effect on cereal yields, and taking a one metre strip out of crop production to establish a sterile, natural regeneration or sown strip, did not significantly reduce yields compared to cropping to the field edge. Conservation headlands generally contained greater amounts of weed biomass than fully sprayed headlands, but grain yields were not significantly reduced. Soil compaction affected yield in one of the field experiments, but not the other, where soil density values were fairly uniform. No relationship was found between fertiliser application and yield. In a survey of cereal headlands, distance from the field boundary was the most important factor affecting yield. Where yield increased with distance from the field boundary, there was a strong linear relationship with log distance (P < 0.001). Weed dry matter was related to distance, and there was a significant relationship between weed dry matter and grain yield in the first year of the survey (p < 0.001), but not in the second. Communities of herbaceous field margin species were established, and the effects of nitrogen fertiliser and sublethal glyphosate application were examined over two years. Cover abundance of grasses was greater than that of dicotyledonous species throughout. Bromus sterilis was the most abundant species in 1995, but by 1996 it had been replaced by Arrhenatherum elatius. Increasing fertiliser rate had a negative effect on total vegetation cover in 1995, due to individual plants lodging. During 1996, fertiliser application increased the cover abundance of the dominant perennial species A. e/atius (p < 0.001), and also the annuals B. sterilis and Galium aparine (p < 0.05). Sublethal doses of glyphosate significantly reduced total cover abundance (P < 0.001), and had a greater effect on grasses compared to dicotyledonous species. Measurement of spray drift into a hedgerow showed that positioning the end of the tractormounted spray boom 2m or 6m away from the crop edge reduced drift into the hedgebottom compared with spraying up to the crop edge (P < 0.001).

With widespread use of pesticides in modern agriculture, the impacts of spray drift have become a topic of considerable interest. The drifting of sprays is a highly complex process influenced by many factors. Advances in aerial application technology and in our ability to measure drift, coupled with the adoption of new technologies for regulating pesticide application have necessitated further research in the pesticide application process. Experiments were conducted to quantify spray drift and describe its movement from aerial applications of pesticide. The effects of spray quality, atomizer type and ground cover were examined. Initial airborne drift amounts were greater than downwind deposits, thus not all of the drifting spray was deposited in the measuring area. Total off-target movement of spray was significantly greater for Fine compared to Coarse sprays. Rotary and hydraulic atomizers, both producing Fine sprays, produced statistically similar off-target movement of sprays. Similarly, no significant statistical differences in spray drift between applications to bare ground and applications to a headed barley crop canopy were not identified. Contrary to expectations, aerial application to bare ground seemed to result in less off-target movement than application to a crop canopy. The vertical spray cloud profiles were similar for all applications with the greatest amount of spray present at the height of release. Spray concentrations diminished from that height upward with diffusion and downward with deposition. The empirical data disagreed with the mechanistic model AgDISP which is currently used in the Canadian regulatory process. The model over-predicted drift deposition by a factor of two to five. Variability in spray deposit values could not be attributed to average differences in meteorological conditions at the time of application. Experiments with appropriate protocols for increased sensitivity may be required to more accurately report subtle differences in drift at distances greater than 200 m from the target area.

Pesticide use is an important component of the agricultural industry. Pesticides are typically applied to crops as a droplet spray, and these droplets are susceptible to off-target movement due to wind, which is called spray drift. It has recently been recognized that shelterbelts may protect vulnerable downwind areas from spray drift. There is a need to characterize the movement of spray drift past a shelterbelt to better understand the extent of this protection and the variables which affect it. The variables investigated in this research may be classified as meteorological conditions, spray application settings, and shelterbelt properties.<p>This research investigated the movement of spray drift past a 5 m tall carragana/chokecherry shelterbelt. Spray was applied using a conventional sprayer that travelled on a path that was upwind and parallel to the shelterbelt. A tracer substance was mixed into the spray solution, and the deposition and airborne concentration of drift was measured using a variety of collectors placed at perpendicular distances up- and downwind of a shelterbelt. The mass of drift deposit on the collectors was determined using spectrofluoremetry and standard solutions.<p>When the spray swath was a distance of 3H (where H is the height of the shelterbelt) upwind of the shelterbelt, it was found that the ground deposition of drift at a distance of 0.5H downwind of the shelterbelt was reduced by approximately 74%, compared to the drift deposit at 0.5H upwind. The reduction over the same downwind distances was 29% in the open field setting. The airborne drift cloud was attenuated by the shelterbelt and the airborne concentration of drift exiting the shelterbelt was reduced by approximately 85% of the entering drift. The airborne drift concentration profile indicated that there was a greater proportion of drift travelling over the top of the shelterbelt rather than passing through the shelterbelt, with the peak concentration occurring at approximately 1.2H.<p>Qualitative and multiple linear regression analyses were used to determine the significance of a number of meteorological and controlled variables on the deposition of drift. It was found that the mass of drift deposited downwind of the shelterbelt increased with a higher wind speed, higher temperature, and lower relative humidity. For the range of meteorological conditions sampled, the effect of wind direction and atmospheric stability were found to be insignificant. Finer spray qualities and higher shelterbelt optical porosity produced greater airborne drift and deposition downwind of the shelterbelt. With increasing upwind sprayer distance, the mass of drift deposited within the shelterbelt decreased.

With widespread use of pesticides in modern agriculture, the impacts of spray drift have become a topic of considerable interest. The drifting of sprays is a highly complex process influenced by many factors. Advances in aerial application technology and in our ability to measure drift, coupled with the adoption of new technologies for regulating pesticide application have necessitated further research in the pesticide application process. Experiments were conducted to quantify spray drift and describe its movement from aerial applications of pesticide. The effects of spray quality, atomizer type and ground cover were examined. Initial airborne drift amounts were greater than downwind deposits, thus not all of the drifting spray was deposited in the measuring area. Total off-target movement of spray was significantly greater for Fine compared to Coarse sprays. Rotary and hydraulic atomizers, both producing Fine sprays, produced statistically similar off-target movement of sprays. Similarly, no significant statistical differences in spray drift between applications to bare ground and applications to a headed barley crop canopy were not identified. Contrary to expectations, aerial application to bare ground seemed to result in less off-target movement than application to a crop canopy. The vertical spray cloud profiles were similar for all applications with the greatest amount of spray present at the height of release. Spray concentrations diminished from that height upward with diffusion and downward with deposition. The empirical data disagreed with the mechanistic model AgDISP which is currently used in the Canadian regulatory process. The model over-predicted drift deposition by a factor of two to five. Variability in spray deposit values could not be attributed to average differences in meteorological conditions at the time of application. Experiments with appropriate protocols for increased sensitivity may be required to more accurately report subtle differences in drift at distances greater than 200 m from the target area.

Pesticide use is an important component of the agricultural industry. Pesticides are typically applied to crops as a droplet spray, and these droplets are susceptible to off-target movement due to wind, which is called spray drift. It has recently been recognized that shelterbelts may protect vulnerable downwind areas from spray drift. There is a need to characterize the movement of spray drift past a shelterbelt to better understand the extent of this protection and the variables which affect it. The variables investigated in this research may be classified as meteorological conditions, spray application settings, and shelterbelt properties.<p>This research investigated the movement of spray drift past a 5 m tall carragana/chokecherry shelterbelt. Spray was applied using a conventional sprayer that travelled on a path that was upwind and parallel to the shelterbelt. A tracer substance was mixed into the spray solution, and the deposition and airborne concentration of drift was measured using a variety of collectors placed at perpendicular distances up- and downwind of a shelterbelt. The mass of drift deposit on the collectors was determined using spectrofluoremetry and standard solutions.<p>When the spray swath was a distance of 3H (where H is the height of the shelterbelt) upwind of the shelterbelt, it was found that the ground deposition of drift at a distance of 0.5H downwind of the shelterbelt was reduced by approximately 74%, compared to the drift deposit at 0.5H upwind. The reduction over the same downwind distances was 29% in the open field setting. The airborne drift cloud was attenuated by the shelterbelt and the airborne concentration of drift exiting the shelterbelt was reduced by approximately 85% of the entering drift. The airborne drift concentration profile indicated that there was a greater proportion of drift travelling over the top of the shelterbelt rather than passing through the shelterbelt, with the peak concentration occurring at approximately 1.2H.<p>Qualitative and multiple linear regression analyses were used to determine the significance of a number of meteorological and controlled variables on the deposition of drift. It was found that the mass of drift deposited downwind of the shelterbelt increased with a higher wind speed, higher temperature, and lower relative humidity. For the range of meteorological conditions sampled, the effect of wind direction and atmospheric stability were found to be insignificant. Finer spray qualities and higher shelterbelt optical porosity produced greater airborne drift and deposition downwind of the shelterbelt. With increasing upwind sprayer distance, the mass of drift deposited within the shelterbelt decreased.

No description available.

Chlorpyrifos (CPF) is a popular organophosphorus insecticide that is heavily used in the agriculture industry as a means of pest control. Chlorpyrifos is known for its toxic effect to inhibit the enzyme acetylcholinesterase (ACHE) in humans and is widely used in areas of California where the site of application is close to occupied areas, such that exposures to residents and bystanders can occur due to secondary drift. Secondary drift refers to the volatilization of a pesticide from the surface to which it was applied (e.g. soil or plant foliage) and subsequent off-site movement in ambient air. Secondary drift is different from spray drift, which occurs during and very shortly after application. The goal of this thesis is to evaluate existing measurements of secondary drift from ambient air measurements of CPF available from California’s Air Monitoring Network (AMN), in comparison to predictions using a state-of-the-art dispersion model. Pesticide use data were obtained from the California Department of Pesticide Regulation (CDPR) website and was compiled to form scenarios to be modeled and compared against measurements taken throughout the year. Probability distributions for the measured and predicted CPF concentrations resulted in correlations ranging from 3% to 91% depending on the year and modeled scenario. Overall the model overpredicted air concentrations for the modeled scenarios, providing conservative values for risk assessment purposes.

Agrichemical spray drift is an issue of concern for the orcharding industry. Shelterbelts surrounding orchard blocks can significantly reduce spray drift by intercepting droplets from the airflow. At present, there is little information available with which to predict drift deposits downwind, particularly in the case of a fully-sheltered orchard block. In this thesis, we develop a simple mathematical model for the transport of airborne drifting spray droplets, including the effects of droplet evaporation and interception by a shelterbelt. The object is for the model to capture the major features of the droplet transport, yet be simple enough to determine an analytic solution, so that the deposit on the ground may be easily calculated and the effect of parameter variations observed. We model the droplet transport using an advection-dispersion equation, with a trapping term added to represent the shelterbelt. In order to proceed analytically, we discretise the shelterbelt by dividing it into a three-dimensional array of blocks, with the trapping in each block concentrated to the point at its centre. First, we consider the more straightforward case where the droplets do not evaporate; solutions are presented in one, two and three dimensions, along with explicit expressions for the total amount trapped and the deposit on the ground. With evaporation, the model is more difficult to solve analytically, and the solutions obtained are nestled in integral equations which are evaluated numerically. In both cases, examples are presented to show the deposition profile on the ground downwind of the shelterbelt, and the corresponding reduction in deposit from the same scenario without the shelterbelt.

Orientador: Evandro Pereira Prado / Resumo: Diversos fatores podem interferir nos depósitos da pulverização em plantas sendo o tamanho de gotas e a ponta de pulverização uma das mais importantes nesse processo. Diante disso, objetivou-se avaliar como o tamanho de gotas e a ponta de pulverização afetarão a quantidade e qualidade dos depósitos da pulverização em plantas de amendoim (Arachis hypogaea L.) nos diferentes estádios de desenvolvimento. A verificação da deposição em plantas de amendoim nos estádios de desenvolvimento dos primeiros ramos (V1) e nos estádios de alongamento de ginóforos (R2) em função do tamanho de gotas (fina, média, grossa e muito grossa – experimento 1) e da ponta de pulverização (TXA 8002 VK - Cônico, TTJ 60 11002 - Plano duplo, AIXR 110025 - Plano com indução de ar, DGTJ 11002 - Plano duplo de deriva reduzida, XR 8003 - Plano de faixa ampliada – experimento 2) foram realizadas em delineamento de blocos inteiramente casualizados com 4 tratamentos e 40 repetições (experimento 1) e 5 tratamentos e 40 repetições (experimento 2), pela pulverização do corante alimentício Azul Brilhante na concentração de 1,5 g. L-1. Os valores de deposição obtidos nos experimentos foram submetidos à análise de variâncias e as médias comparadas pelo teste de Scott-Knott. A uniformidade de distribuição dos depósitos foi ajustada a regressão logística. No primeiro experimento (tamanho de gotas × estádios fenológicos) as médias de deposição no estádio V1 foram todas significativamente diferentes ente si, e no estádio R... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Several factors can interfere with spray deposits on plants. It is known that the droplet size and the spray tip are some of the most important in this process. Therefore, the objective was to evaluate how the droplet size and the spray tip will affect the quantity and quality of spray deposits on peanut (Arachis hypogaea L.) plants at different stages of development. The verification of deposition in peanut plants in the stages of development of the first branches (V1) and in the stages of elongation of gynophores (R2), depending on the droplet size (fine, medium, coarse and very coarse - experiment 1) and the spray tip (TXA 8002 VK - Conical, TTJ 60 11002 - Double plane, AIXR 110025 - Air induction plane, DGTJ 11002 - Double reduced drift plane, XR 8003 - Extended range plane - experiment 2), were carried out in a completely randomized block design with 4 treatments and 40 repetitions (experiment 1) and 5 treatments and 40 repetitions (experiment 2), by spraying the Brilliant Blue dye food at concentration of 1.5 g L-1. The deposition values obtained in the experiments were subjected to analysis of variances and their averages were compared by the Scott-Knott test. The uniformity of deposit distribution was adjusted to logistic regression. In the first experiment (droplet size × phenological stages), the deposition averages in the V1 stage were all significantly different from each other; in the R2 stage, the treatments with fine and medium droplets differed from the treatm... (Complete abstract click electronic access below) / Mestre