Evaluation of Plastic Tarps, Reduced Rates and Low-Impact Application Methods of Soil Fumigants on Loblolly Pine Seedling Production

ABSTRACT

Due to the world-wide phase-out of (methyl bromide) MBr use and new soil fumigation rules established by the US Environmental Protection Agency (EPA) to reduce bystander risk, a large-scale study comparing five fumigants using new plastics, reduced rates and low impact application techniques over three growing seasons was installed to determine the effects that these factors have on seedling quality and quantity. Seedling densities at the end of the first growing season in 2010 ranged from 190-261 seedling/m2 with some treatments out-performing others with respect to number of seedlings. At the end of the third growing season in 2012, the best soil fumigant for producing loblolly pine (Pinus taeda L.) seedlings was chloropicrin at 280 kg/h and MBr at 168 kg/h under totally impervious film (TIF). Overall, seedling root length, surface area, root diameter and root tips were similar to the standard MBr 280 treatment for all soil fumigants except for the Chlor 60 treatments under high density polyethylene (HDPE) plastic. The numbers of Culls was less with the higher rates and there was a corresponding increase in the number of Grade 1 and Grade 2 seedlings for each soil fumigant. These trials indicate that, while not the perfect replacement in all nursery soils, seedling production is still possible without MBr if alternatives such as chloropicrin are used and managers pay close attention to weed and nematode pests that are less susceptible to chloropicrin than MBr. Higher rates of each soil fumigant were better than the lower rates.

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