Effect of soil moisture condition on the conversion rate of oxamyl.

The decomposition of oxamyl in four soils under moist conditions was measured in incubation experiments at 15 deg C. Half-lives of oxamyl in soils with moisture tensions of approx. -9.8 X 103 Pa were 13 days in a clay loam, 14 days in a loamy sand, 34 days in a peaty sand and 39 days in a humic loamy sand. The rate of oxamyl decomposition in the clay loam decreased with decreasing soil moisture content down to values for below wilting point. Oxamyl decomposition in the humic loamy sand decreased with decreasing soil moisture content, but increased sharply in the very dry range. (Abstract retrieved from CAB Abstracts by CABI’s permission

Meting van spuitdrift met verschillende collectoren bij verspuiten van kleurstoffen en bestrijdingsmiddelen

Spuitvloeistoffen kunnen met een kleurstof worden gemerkt, waarna eenvoudig en goedkoop de drift kan worden bepaald via opvang (depositie) van de spuitdruppels op collectoren. Onderzocht werd in hoeverre deze werkwijze de werkelijke drift van bestrijdingsmiddelen weergeeft. met een vaststaande spuitopstelling werden vier bespuitingen uitgevoerd met spuitvloeistoffen met daarin enkel de kleurstoffen Brilliant Black en Brilliant Sulfoflavine of het bestrijdingsmiddel parathion en combinaties van deze stoffen. Spuitdrift werd gemeten op twee afstanden met verschillende typen collectoren. De kleine verschillen in deposities gemeten via de kleurstoffen of via parathion waren hoofdzakelijk toe te kennen aan kleine meetnauwkeurigheden. Op opgehangen bolvormige driftcollectoren van gevlochten kunststofdraad werd 20% meer depositie gemeten dan op cilindervormige collectoren van roestvrijstaalgaas. Tussen de deposities van op de grond liggende collectoren van filterdoek, filtreerpapier en aluminiumfolie waren geen significante verschillen

Volatilization of fenpropimorph and clopyralid after spraying onto a sugar beet crop

Volatilization rates of pesticides were measured with two micrometeorological methods. For fenpropimorph, the highest rates (1.3-3.0% per hour) were measured in the first hours after application. The rate gradually declined to less than 0.01% per houron the sixth day. Clopyralid had much lower volatilization rates. They were highest (0.1% per hour) on the day after the day of application and declined below the detection limit (less than 0.01% per hour) on the sixth day after application. Rates calculated with the aerodynamic method were slightly higher than those calculated with the Bowen ratio

Volatilization of tri-allate, ethoprophos and parathion measured with four methods after spraying on a sandy soil

At about eleven times after application of tri-allate, ethoprophos and parathion to a sandy soil, their rates of volatilization were determined by the aerodynamic method (AD), the Bowen-ratio method (BR), the theoretical-profile method (TP) and the Box method. The volatilization was highest for tri-allate and lowest for parathion. On the first day after application, the volatilization rate decreased sharply, but thereafter the decrease was more gradual. The differences in volatilization rate as determined with the AD, BR and TP methods were comparatively small. The rates determined with the Box method were mostly lower than those determined with the other methods

Volatilization of parathion and chlorothalonil after spraying onto a potato crop

At fourteen times after application of parathion and chlorothalonil to a potato crop their rates of volatilization were determined by the aerodynamic and Bowen ratio methods. The highest volatilization rate of parathion occurred shortly after application. In the first hours after application its volatilization rate decreased sharply; thereafter it decreased more gradually. The volatilization rate of chlorothalonil at one week after application did not differ much from that shortly after application. Weather conditions in the first twenty-four hours after application of both pesticides were simulated in a chamber. The volatilization of parathion in the chamber had the same order of magnitude as that determined in the field

Transport of water, bromide ion, nutrients and the pesticides bentazone and imidacloprid in a cracking, tile drained clay soil at Andelst, the Netherlands

The aim of this study was to perform a field experiment to collect a high quality data set suitable for validating and improving pesticide leaching models and nutrient leaching models for drained and cracking clay soils. The transport of water, bromide, nutrients and the pesticides bentazone and imidacloprid was studied on a 1.2 ha experimental plot. Moisture profiles and groundwater tables were measured, starting in November 1997. Winter wheat was sown on 23 October 1997 and harvested on 20 August 1998. Bentazone and bromide were applied at 7 April 1998; imidacloprid was applied at 27 May when the soil was almost completely covered by the crop. The amount present in soil was measured within 2 days after application (32 sampling cores) and was found to vary between 80% of the nominal dose (imidacloprid) to 110 % (for bentazone). Manuring and soil cultivations were as usual for the wheat crop. Soil profiles were sampled at eight times (16 cores at each date, last in April 1999). Drain flow was continuously recorded and the water flow proportionally sampled for analysis of the test compounds. Groundwater was sampled periodically from sets of permanently placed filters at four depths at 16 sites. Sorption isotherms of the pesticides were measured with soil from 0-25 cm. Transformation rates of the pesticides were measured at different temperatures in soil material from topsoil and subsoil layers. Soil hydraulic properties and shrinkage characteristics were measured in the laboratory. Meteorological data (i.e. rainfall, air temperature, global radiation, air humidity etc.) groundwater levels and soil temperatures at three depths were monitored continuously. After 56 days, about 80% of the bromide dose was taken up by the crop, which demonstrates that bromide is not a suitable tracer in cropped soil during the growing season. After that time the bromide was gradually released again into the soil. Preferential transport through cracks and macropores of all test compounds was measured both in summer and in winter. This resulted in the highest concentration of bromide and bentazone measured in drain water already 21 days after application following 56 mm rainfall. Imidacloprid was already detected in groundwater at 1.3-1.5 m depth, 11 days after application, following 65 mm rainfall. High peaks in nitrate concentrations in the groundwater at 1.00-1.50 m depth and in the drain water were detected within 14-18 days after the first fertilizer application, following 94 mm of rainfall. Extreme high peaks in concentrations of ortho-P and soluble organic-P were measured in the drain water at respectively 2 days and 37 after slurry application (the only phosphorus application during the experiment). For nitrate concentrations in the drain water there were indications for bypass by preferential flow of `clean` rainwater to the drains

Choice of tracers for the evaluation of spray deposits

Tracer substances, used to evaluate spraying effectiveness, ordinarily modify the surface tension of aqueous solutions. This study aimed to establish a method of using tracers to evaluate distribution and amount of spray deposits, adjusted to the surface tension of the spraying solution. The following products were tested: 0.15% Brilliant Blue, 0.15% Saturn Yellow in 0.015% Vixilperse lignosulfonate, and 0.005% sodium fluorescein, and mixtures of Brilliant Blue plus Saturn Yellow and Brilliant Blue plus sodium fluorescein at the same concentrations. Solutions were deposited on citrus leaves and stability was determined by measuring fluorescence and optical density of solutions without drying, dried in the dark and exposed to sunlight for 2, 4 and 8 h. These values were compared to those obtained directly in water. The static surface tension of the tracer solution was determined by weighing droplets formed during a period of 20 to 40 seconds. The Brilliant Blue and Saturn Yellow mixture at 0.15% was stable under all conditions tested. It was not absorbed by the leaves and maintained the same surface tension as that of water, thus permitting concentration adjustment to the same levels used for agrochemical products, and allowing the development of a qualitative method based on visual evaluation of the distribution of the pigment under ultraviolet light and of a quantitative method based on the determination of the amount of the dye deposited in the same solution. Spray deposition could be evaluated at different surface tensions of the spraying solution, simulating the effect of agrochemical formulations