Refer to "Stale and False Seedbeds" in Section P. Vegetable Crops for information on the following options.
ammonium nonanoate, ammonium salts of fatty acids
caprylic and capric acids
clove oil, peppermint oil, rosemary oil, thyme oil
decanoic acid, octanoic acid, pelargonic acid
paraquat (restricted-use herbicide in Idaho and Oregon for acute toxicity)