A simple and reliable device for monitoring fumigant residues in soil.

Soil fumigat ion is commonly used to cont rol soil pests such as nematodes and o t h e r soil-borne pathogens . Most fumigants are phytotoxic , however , and fa rmers must delay subsequent plant ing until the dange r has subsided. T h e ability to measure phytotoxic levels o f fumigant residues could minimize the waiting time, bu t no accura te and practical m e t h o d o f m e a s u r e m e n t is available. Bioassay me thods such as the cress test (5) and the onion test (2) are difficult to apply and the i r applicat ion remains exper imenta l . In t ry ing to develop a simple de tec t ion me thod , we found that a ceramic gas sensor (3) deve loped for gas alarms (1) could be modif ied into a device for rapid and accura te moni to r ing o f fumigan t residues