Volatilization of Microencapsulated and Conventionally Applied Chlorpropham in the Field1

Abstract The effectiveness of preemergence applications of herbicides to soil surfaces may be seriously reduced by losses due to volatilization to the air. Direct measurements of volatilization rates of two chlozopropham (isopropyl‐m‐chlorocarbanilate) formulations, a microencapsulated and a conventional emulsifiable concentrate, were made to establish the differences in volatilization rates in the field. During the first day after application to a bare silt loam soil, without cultivation, on 25 May, the volatilization from the encapsulated residues was about one.third that from the emulsified material. Volatilization decreased rapidly over the first 3 days, when 60% of the encapsulated and 30% of the emulsified chlorpropham remained in the target area. Volatilization was still measurable after 50 days, when 20% of the encapsulated and 2% of the emulsified remained. Over this whole period the emulsified residues volatilized about five times faster than the encapsulated. The results indicate the potential value of microencapsulaton techniques for controlling vapor losses and increasing the persistence of volatile herbicides in the field.