Physico‐chemical aspects of the availability of pesticides in soil. II.—controlled release of pesticides from granular formulations

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Abstract
The extent to which formulation factors control the release of a toxicant from granular formulations, under the leaching action of rain, has been investigated. Using granules prepared by an agglomeration process and containing the herbicide chlorthiamid, the rate of release can be varied by changing the filler base and by the use of different binding agents. By varying the binding agent a considerable degree of control can be exercised over the release of chlorthiamid.The release of toxicant is partly by direct leaching from the granule and partly by disintegration of the granule in water which renders the toxicant more accessible.The extent to which the release of other toxicants may be controlled in a similar way has been examined using ‘Bidrin’, fenuron, 2,4‐D, chlorfenvinphos and N‐tritylmorpholine. Toxicant release appeared to be governed by the filler/binding agent combination used in the granule and by the water solubility of the toxicant. Where the toxicant solubility is high, control over release is difficult to achieve but where the solubility is below 2000 ppm, a considerable control is possible.