Predicting Fumigant Transport and Pathogen Control in Soils.

There have been great concerns about negative environmental impacts from soil fumigation. Chemical alternatives for methyl bromide must have fewer human and environmental health risks while offering sufficient pest control efficacy. An integrated approach is needed to predict not only fumigant transport and fate and but pathogen control without conducting elaborate and costly experiments.  The objectives of this study are to 1) develop a mathematical model to describe the fumigant movement and pest control and 2) test the accuracy of the model by comparing the results from the prediction with those from the experimental measurement. Both analytical and numerical methods were used to predict the fumigant movement. The concentration-time index was used to predict the pathogen control. A 2-D experimental system (60 x 60 cm) was developed to measure the volatilization, soil gas concentration, degradation and mortality ratio of barnyard grass, citrus nematode, and Fusarium oxysporum. Such model can be used to test emission reduction strategies such as organic matter addition, surface irrigation, plastic tarps, and ammonium thiosulfate addition to minimize the fumigant emission and optimize the pest control efficacy.