The breakdown of the triazine herbicide cyanazine in soils and maize

Abstract

Radioisotope techniques have been used to study the breakdown products that are formed from the herbicide cyanazine (BLADEX)", 2-chIoro-4-( 1 -cyano-Imethylethyl-amino)-6-ethylamino-l,3,5-triazine, in soils and in maize grown in the soils under indoor conditions.In soils of different types cyanazine broke down mainly by conversion of the nitrile group to amide (11) and then to an acid (111) followed by hydrolysis of the ring chlorine to hydroxyl (IV). Dealkylation reactions occurred to only a limited extent in soils.In maize plants grown in treated soils the hydrolysis products, the amide (U) and the hydroxy acid (IV) were detected as well as appreciable quantities of products (VI) and (VIU) formed from these by loss of the N-ethyl group. In plants the hydroxy acids (IV) and (VIII) were present in the free form and there was also evidence for conjugates which were not identified but could beconverted to these hydroxy acids, (IV) and (VIM), on treatment with acids.

Spatial Variability of Cyanazine Dissipation in Soil from a Conservation-Managed Field

“…***NSS found in raw data 0.57). Cyanazine half-life, nonextractable 14 C at day 28, and soil pH tended to be higher in soil sampled from downslope, while cyanazine amide at day 5 and hydroxy cyanazine at day 28 were lower. Linear correlations between cyanazine half-life and clay were positive, while half-life was lower with increasing sand (Table II).…”

“…> F = 0.0001), and support previous studies where clays had a higher capacity for cyanazine sorption (25). Several other parameters, such as extractable cyanazine amide at days 5 and 28, extractable hydroxy cyanazine derivatives and nonextractable 14 C at day 28, soil pH, and cyanazine half-life, had significant (Pr. > F = 0.0001), but moderate, surface response regressions as a function of direction across the field (R 2 range from 0.40 to Value is the effective range when exponential model is used.…”

“…The half-lives of extractable total 14 C and extractable 14 C cyanazine data were fit to first-order kinetics using PCSAS NLIN procedure (SAS, Cary NC) (23). The first order degradation rate constant (K) and the 95% confidence interval were calculated using the NLIN procedure, and the half-life was calculated from K. Evidence of spatial structure in the data was assessed in two steps.…”

“…Ten mL of 14 C cyanazine solution (10 μmol L -1 cyanazine; 162 kBq g -1 ) were added to the tubes and shaken for 24 hours at 25 o C. After centrifugation (8,000 x g; 10 min), radioactivity in aqueous samples was determined by liquid scintillation counting. Cyanazine K d values were calculated as the distribution between cyanazine in solution at equilibrium and cyanazine sorbed to soil.…”

“…Degradation of cyanazine is generally thought to be a nonbiological process, primarily hydrolysis, to amide and hydroxyl metabolites (14,15). Soil parameters such as OM, pH, and water content play a role in the fate of cyanazine in the agricultural environment (16,17).…”