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.

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Crops and soils from field trials in 1967-1970 in several countries have been analysed for residues of the triazine herbicide cyanazine ('BLADEX'" or 'FORTROL'"' 2-chloro-4-(l-cyano-1-methylethylamino)-6-ethylamino-l,3,5-triazine) and for its degradation products 2-chloro-4-( l-carbamoyl-l-methylethylamino)-6ethylamino-1,3,5-triazine (11), 2-chloro-4-( 1-cyano-1 -methylethylamino) -6-amino-l,3,5-triazine (V) and 2-chloro-4-(1-carbonyl-l-methylethylamino)-6amino-l,3,5-triazine (VI).The time for the concentration of cyanazine in soils to fall to half the initial value was in the range 1.3 to 5 weeks with a mean value of 2.4 weeks. The rate of loss was not affected by sparse crop cover and there was some indication that the rate was greater under moist soil conditions.Residues of up to 0.5 part/million of (11) and up to 0.08 part/million of (VI) were detected in soils at 4 weeks from cyanazine application at 2 kg/ha. The residues of cyanazine and the degradation products declined rapidly and were 0.07 part/million or less at 16 weeks from treatment. Repeated annual applications did not lead to a detectable build up of residues in soil.Neither residues of cyanazine nor those of (11), (V) or (VI) could be detected in a wide range of crops harvested from soil treated in accordance with the likely recommendations and the limits of detectability were 0.01 to 0.04 part/million.

The persistence, penetration, and breakdown of the herbicides chlorthiamid (‘Prefix’, 2,6‐dichlorothio‐benzamide) and dichlobenil (‘Casoron’, 2,6‐dichlorobenzonitrile) have been studied in the field in clay, medium loam, sandy loam, and peat using applications of unincorporated granules and wettable powders at 9 kg/ha (active material). Conversion of chlorthiamid to dichlobenil was rapid in the soil. After 4 weeks, less than 3% remained of chlorthiamid that was applied to clay, medium loam, and sandy loam and less than 17% remained in peat. The initial half‐life of dichlobenil residues (following dichlobenil application) and ‘total nitrile’ residues (chlorthiamid + dichlobenil residues following chlorthiamid application) under wet conditions was near 2 weeks in clay, medium loam, and sandy loam, and ranged from 3‐20 weeks in peat for different applications. There was very little penetration of chlorthiamid or dichlobenil below the 4 in depth of the soil within 32 weeks of the single application of herbicides except in peat. 2,6‐Dichlorobenzamide was formed in all four soil types after application of either chlorthiamid or dichlobenil. At 8‐10 weeks after application the benzamide residues in the soil were generally greater than those of the dichlobenil, except in peat. In clay, which was studied in most detail, the benzamide penetrated to greater depths than did the dichlobenil or chlorthiamid.