FACTORS AFFECTING THE LOSS OF TRI-ALLATE FROM SOILS

Summary. Electron-capture gas chromatography was used to detect tri-allate residues in persistence studies with two soils. At rates equivalent to 0–75, 15 and 3 Ib/ac, 50% of the amount applied was degraded in 8–11 weeks at 25°C in moist Regina heavy clay and Weyburn loam. No loss occurred in sterile soils, indicating that microbial degradation may be a, major factor contributing to tri-allate breakdown.
When aqueous solutions buffered at pH 4–8 were held at 25° G, only 10–15% of the tri-allate was chemically degraded during 24 weeks.
At the normal field rate of 1·25 Ib/ac, tri-allate was not readily leached. From soil columns of Weyburn loam, 5–7% was eluted by 9 in. of water; with clay the corresponding value was 12–13% of the amount applied. When field plots were sprayed with 125 lb/ac in April, tri-allate could still be detected until the soil froze in November.
Facteurs agissant sur la perte de tri-allate dans les sots     

THE BASIS OF THE DIFFERENTIAL PHYTOTOXICITY OF 4-HYDROXY-3,5-DI-IODOBENZONITRlLE*

Summary. Entry of ioxynil-¹⁴C into portions of leaves was greater with mustard than with barley or pea and was unrelated to stomatal density. Measurement of ioxynil content of sprayed plants showed that by increasing the concentration of ioxynil and adding a surfactant, almost as much ioxynil could be made to enter barley as entered mustard from a lower concentration without surfactant. Auto radiographs showed that a limited amount of ¹⁴C was translocated to a small extent in plants following localized application of ioxynil-¹⁴C. An experiment comparing leaf removal by cutting with destruction of equivalent leaf areas by ioxynil treatment suggested a greater translocated effect of ioxynil with mustard than with pea or barley. Les principes de la phytotoxicité différentielle du 4-hydroxy-3,5-di-iodobetZonitrile II. Absorption et migration     

ADSORPTION AND DESORPTION OF SIMAZINE BY SOME ROTHAMSTED SOILS

Summary. The adsorption of simazine from, and subsequent desorption into, 0–01 M calcium chloride solution was investigated using twenty-three Rothamsted soil samples from sites differing greatly in cropping history and manurial treatment. Organic carbon content was the only factor related to the ability of the soils to sorb simazine; this accounted for 90% or more of the variation between soils Equilibrium was attained during adsorption in from fewer than 2 to more than 24 hr. Equilibrium during desorption was only occasionally attained within 24 hr. Differences between theoretically predicted and measured concentrations of simazine in solution following desorption were least for soils that attained equilibrium fastest during adsorption. Differences in adsorption and desorption kinetics between soils could not be related to soil pH, organic carbon content or cropping and manuring history. Comparisons of unlimed and limed soils suggested that no simnazine was lost by acid hydrolysis during the experiments.
Adsorption et désorption de la simazine par quelques sols de Rothamsted