Fig. 9. Effects of application depth on concentration–time exposure index (CTEI) of the top-100-cm profile of a sandy loam soil calculated for 1,3-dichloropropene efficacy against citrus nematode (Tylenchulus semipenetrans) using a threshold air-phase CT value of 12 µg h cm^–3 obtained from a field study (Wang and Yates, 1999). Fields are 102-cm-wide beds. Application dosage = 327 kg ha^–1.