Abstract
The germination of rice and corn seeds within the graded moisture range between 11 and 15% was tested after they were fumigated with phosphine and methyl bromide at their different concentrations, exposure times and temperatures. The sorption of the fumigants by both seeds was also studied. The viability of rice seeds with 11 and 15% moisture was not impaired by phosphine with its concentration up to 200mg/l. Corn seeds were also tolerant to the fumigant when their moisture content remained 11%. With the 15% moisture their viability was affected drastically at both 30°C and 35°C. Rice seeds were more sensitive to methyl bromide than corn seeds. To maintain their reasonable viability when exposed to up to 5mg/l of methyl bromide at 25°C and 30°C for 5 days, moisture of the rice seeds should not be higher than 11%. Corn seeds were generally viable when exposed to up to 10mg/l of methyl bromide at 25°C and 30°C for 5 days when their moisture content was kept not higher than 13%. The rate of sorption was found to be related to the viability decline of both seeds. Rice seeds sorbed less phosphine than corn seeds and likewise were less affected. As for the methyl bromide sorption the reverse was true. The effects of seed moisture, exposure temperature and time, and types of sorption were also discussed in this paper.
