Wheat and oat straw, soybean and sweetclover hay, corn and sorghum stalks, bromegrass and sweetclover stems were extracted with hot and cold water, using 1 part of residue to 15 parts of water. One-half of the water extract of each residue was autoclaved for 1 hour at 20 pounds steam pressure. In addition, wheat straw was extracted with ethanol and the extract was separated into strong and weak acids, neutral, basic, and water-soluble compounds. The ethanol-soluble compounds were tested for their effect on wheat, whereas the hot and cold water extracts of residues were tested for their effect on germination and growth of wheat, sorghum, and corn seeds.
All the residues contained water-soluble substances that inhibited the germination and growth of sorghum, corn, and wheat. The cold water extracted more toxic materials than did the hot water. Autoclaving increased the toxic effect of the water extract of residues on root growth. The toxic effect on germination and shoot growth was decreased for most residues by autoclaving of aqueous extract. Ethanol-soluble substances of wheat straw inhibited the germination and growth of wheat seeds. The ethanol extract of wheat straw, separated into strong acid, water-soluble, neutral, weak acid, and basic compounds, showed decreasing toxicity in the order listed.