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14 POTATO GROWER | NOVEMBER 2020 Pillars of Metam Movement in Soil By Kyle Coleman Director of Marketing and Commercial Development, NovaSource TOP 5 Although metam fumigants—metam sodium and metam potassium— have proven to be extremely reliable for suppressing weeds, disease and nematodes in potato fields for more than four decades, recent discoveries have confirmed that there aren't just one or two ways to apply the product to maximize effectiveness. Conventional wisdom has been that you shank it or chemigate it, and you let metam do its thing. It actually sounded pretty simple, and the product often performed well enough to keep applying it again and again, based upon the assumption that the product was going to travel where it needed to be to suppress a wide variety of pests. However, upon taking a closer look during the past several years, we learned that the art of metam application to achieve maximum results is more complex. New insights about post-application metam movement in soil are, in a way, "groundbreaking." Many applicators have assumed that upward, downward and lateral movement of the products would be uniform over distances from 6 to 12 inches. Another common assumption has been that the product would remain in the soil, suppressing pests regardless of soil conditions. In 2017, I began to wonder what was going on underground following metam applications when several Washington onion operators began questioning whether the product was losing effectiveness. They weren't getting the results they expected. I acquired a miniRAE photoionization detector (PID) after learning of this technology from researchers at major universities and began going to fields to measure the presence of metam at different soil depths during the hours and days following application. The readings were startling and revealed some dramatic insights into the results that applicators were, and in some cases were not, getting. After three years of study, tracking post-application metam movement in nine states, and collecting more than 40,000 soil samples taken between myself, coworkers, growers and distributor cooperators under different conditions, Five Pillars of Metam Movement 9/15/20 Five discoveries, resulting from more than three years of study and 40,000+ soil readings compiled by NovaSource, provide new insights for optimizing the effectiveness of metam product application: Moisture Preservation Placement Strategy Pest Respiration 1 2 4 3 Soil Tilth 5 Equipment