1,3-dichloropropene and chloropicrin emissions following simulated drip irrigation to raised beds under plastic films.

Using laboratory soil chambers a nonscaled representation of an agricultural raised bed was constructed. For a sandy loam soil, 1,3-dichloropropene (1,3-D) and chloropicrin (CP) were applied at 5 cm depth with an excess of water (simulated drip irrigation). Application was made under both high density polyethylene (HDPE) and virtually impermeable film (VIF) covering the soil bed (the furrow was left uncovered). Soil gas distribution of the fumigants, together with emissions into the headspace above the bed, sidewall and furrow were determined over time. Total emissions from the HDPE treatment were cis 1,3-D 28%, trans 1,3-D 24%, and CP 8%. Due to its lower permeability, the values for VIF were 13%, 7%, and 1.5%, respectively. With HDPE, the majority (86-93%) of the emissions occurred from the bed, while for VIF the majority (92-99%) of the emissions was from the furrow. Compared to a range of literature values for shank injection, the use of drip application appears to offer a benefit in reducing 1,3-D and CP emissions. However, the most meaningful comparison is with our previous data for simulated shank injection where the same soil was covered (completely) with the same plastic films (1). In this comparison, only 1,3-D emissions under HDPE were lower with drip application; 1,3-D emissions under VIF and CP emissions under both films were greater with the drip application.