1,3-DICHLOROPROPENE DISTRIBUTION IN SOIL WHEN APPLIED BY DRIP IRRIGATION OF INJECTION IN PINEAPPLE CULTURE

The fumigant nematicide, 1,3-dichloropropene (1,3-D VL; 'Telone' II) a nd a soluble liquid formulation, 1,3-D SL were tested in a pineapple f ield experiment to evaluate the vapor movement of the two formulations in soil gas as well as the movement and persistence of 1,3-D SL in so il profiles. Prior to planting, 1,3-D VL (407 kg ha-1) was hand-inject ed into the soil in two parallel rows per planting bed to approximate the practice of chisel injection. 1,3-D SL (407 kg ha-1) was applied w ith 6 mm of water by drip irrigation through a drip tube in the center of the bed. Post-plant applications of 1,3-D SL (113 kg ha-1) were ma de at three-month intervals during a two-crop cycle. 1,3-D concentrati ons in soil gas were lower at the plant line in the drip treatment com pared with the 1,3-D VL treatment, owing to differences in application method and fumigant placement. 1,3-D in the vapor phase reached peak concentrations 24 h after injection in the 1,3-D VL treatment compared with a peak at 48 h in the drip treatment. Post-plant applications of 1,3-D SL resulted in a three-fold difference in peak 1,3-D soil gas c oncentrations between replicate applications, the concentration being inversely related to soil moisture at the time of sampling. Drip appli cation of 1,3-D SL resulted in a relatively uniform distribution of 1, 3-D across the bed and to a depth of 45 cm. There was no effect of for mulation on downward movement of 1,3-D and persistence in soil profile s sampled two weeks and one month after application. Rainfall which oc curred 9 days after pre-plant 1,3-D fumigation resulted in leaching of 1,3-D to a depth of 150 cm in soil profiles. Due to the short half-li fe of 1,3-D, significant penetration of 1,3-D in the soil was observed only when irrigation or rainfall occurred soon after application.