Field Evaluation of VIF in California
Our team has conducted many evaluations of impermeable films in California strawberry. Listed below is research that was conducted to compare the efficacy of low application rates of registered fumigants applied under VIF and STD films for strawberry production.
Field research and demonstration trials were conducted at two commercial fields in central coastal California near Salinas at the USDA-ARS Spence Farm and near Watsonville at the Monterey Bay Academy (MBA) research facilities during the 2007/2008 growing season. Fumigants were applied at MBA on October 11, 2007 and at Spence farm on October 24, 2007. The fumigants tested were InLine (200 lbs/A), MB/Pic (drip formulation, 50/50) (200 lbs/A), Pic (150 lbs/A), Pic-Clor60 (150 lbs/A). The efficacy of all treatments were compared to MB/Pic 67/33 (300 lbs/A) applied by drip fumigation. Each fumigant was applied under two types of film: a 1.25-mil virtually impermeable film (VIF) provided by BrunoRimini, Ltd., Italy; and a 1.25-mil standard polyethylene tarp. Approximately four weeks after fumigation, bareroot strawberry variety “Albion” was transplanted with 12-inch spacing in two planting lines per bed spaced 16” apart. Beds were 54 inches center-to-center and 30 ft long at MBA and 100 ft long at Spence farm. Final harvest plot size was 20 ft long at MBA and 35 ft long at Spence farm. Treatments were arranged in a split plot design with film as the main plot and fumigant as the subplot. Treatments were replicated four times. Conventional tillage practices for strawberry production for the area were followed. Fruit yield was evaluated once or twice weekly and separated into marketable and culls. Fruit yield data were analyzed using SAS version 9.3. Data were analyzed for the effects of film on season long fruit yields and mean separation was performed using LSD. The emissions data were analyzed in EXCEL using a student’s T-test.
The permeability of films used in this study to 1,3-D, CP, IM, and MB vapors was measured using static sealed chambers at 22 ± 2oC as described by Papiernik et. al. (2001). The mass transfer coefficient (MTC, cm h-1) for all fumigants studied varied between 3.3 to 18.8 cm h-1 for commercial standard polyethylene tarp, but less than 0.001 cm h-1 for VIF (Table 1). The average MTC of VIF was <1% of the average MTC of standard commercial tarp. The effect of film on fruit yield was not significant (data not shown).
The conclusions of this work with VIF suggest that it does indeed trap fumigants, but did not necessarily result in improved yields. The work on TIF that were reported recently suggest that TIF trapped fumigants under the film resulting in higher fumigant concentrations, which resulted in higher strawberry fruit yields and better weed control than standard films (Fennimore and Ajwa 2011). The VIF tested here was a three layer film with only one impermeable layer, while the TIF was a five layer film with two impermeable layers which may have resulted in greater tolerance to stretching in TIF than VIF.