In front of several greenhouse scaffolds, Steve Hamra gestured to a metal cart containing trays of seedlings for bell peppers, tomatoes and romaine lettuce. About 150 miles south of St. Louis on a 10-acre site, Hamra is growing produce hydroponically, or in water instead of soil, for about 400 schools, in Missouri and other states.
 
Hamra, president and founder of Amanzi Farms, hopes to expand its operations to Kansas City and Springfield. But he’s worried that his vegetables could be damaged by the herbicide dicamba, which some neighboring farms are using.
 
The chemical is sold under brand names, such as Monsanto’s XtendiMax, BASF’s Engenia and DuPont’s FeXapan. It’s very effective at killing pigweed, a tough plant that many soybean farmers grapple with. However, it’s hard to control, since it turns into a gas in hot weather and can drift miles off target, causing damage to sensitive crops.
 
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