Improving Fumigation Efficiency by Increasing Drip-tape Number and Using Low-permeability Film in Raised-bed Production Systems

Drip fumigation is commonly used for controlling soilborne pests in raised-bed strawberry production system in California. However, the high emission loss and poor pest control indicate that the current fumigation practice with two drip tapes and polyethylene film (PE) covering need to be improved. In September 2014, a field trial was conducted in a grower’s field in Oxnard, CA, to evaluate fumigant emission, distribution, pest control and strawberry yield by doubling the drip-tape number and covering beds with low permeability film (LPF). The treatments included application of Tri-Clor EC (a mixture of 94% chloropicrin and 6% inert ingredients) at a full rate (224 lbs/acre) or a half-rate (112 lbs/acre) through either two or four drip tapes under LPF, a full rate through two drip tapes under PE, and a non-fumigated control under LPF. The LPF dramatically reduced chloropicrin emissions compared to PE covering. The peak emission flux in LPF covered beds was about 10% of that in PE covered beds, while no emissions were detected from uncovered furrows from all treatments. Fumigant concentration in the LPF beds at half-rate was still higher than that in the PE beds at full rate. The four drip-tape layout was found to further improve fumigant concentration and vertical distribution compared to the two drip-tape layout. The four drip-tape layout showed the best nutsedge control at either full or half rate. Strawberry yield during early growth season in LPF beds were higher than in the PE beds and non-fumigated control. The overall results imply that the combination of increasing drip-tape number and covering beds with LPF can further improve fumigation efficiency or use reduced rates in raised-bed production systems.