Note: This is my advice to a person who had inadvertently added Sulfentrazone-treated grass clippings to their compost pile. I thought I would include it here, as there is not much information on Sulfentrazone on the web.
I have a big problem with persistent herbicides. They stay in the soil for months or even years Persistent herbicides should absolutely not be legal for home use (or pretty much any other use, IMHO). Ortho nutsedge killer seems to be formulated with Sulfentrazone. From the EPA:
“Based on the current environmental fate data base, sulfentrazone has the following characteristics: 1) moderately soluble, 2) not susceptible to hydrolysis, 3) extremely susceptible to direct photolysis in water, 4) very stable to photolysis on soil, 5) aerobic half-life of 1.5 years, 6) anaerobic half-life of 9 years, 7) very high mobility in soil (average Koc = 43, Kd < 1), and 8) low volatility from soils and water. With these properties, it appears that sulfentrazone is highly mobile and persistent, and has a strong potential to leach into groundwater and move offsite to surface water.”
Seems like it is also implicated in being toxic to aquatic life and a potential reproductive/developmental toxin, all on the EPA website. If you have very little space to work with, I’d chuck the clippings and any compost exposed to them. If you have a little space, though, I’d let them sit.
How integrated are the clippings in your compost? If they are just sitting on your pile, I’d just do my best to scrape them off and move them to a place where they are unlikely to leach and let them sit for a few years (probably in my dog/humanure aging area). If they are thoroughly mixed in, I’d start a new pile and let the contaminated one age, turning it regularly to keep it aerobic and watering it to keep microbial activity up. After a year or so you can try doing assays by planting pea or bean seeds into the compost to see if the herbicide is still active.
I’m not a huge fan of sending organic matter to the landfill, so I try to give things time, sun, heat, and water. I’ve dealt with enough herbicide contamination recently that I no longer use any manure, hay, or grass clippings without letting them sit for at least a few years first.
It’s pretty sad that we can no longer trust such basic organic materials and that our culture seems to think poisoning our soil is fine. It’s corporate greed: dollars now at the expense of the ability for citizens garden and produce our own food and as such is undemocratic and and exploitative. Presumably they then want us to buy the food they produce, since we are unable to grow our own because we have poisoned our own soil. For Big Ag it’s a win-win, for us just a loss.