Kochia can be a 'killer' on spring wheat
In their second study, the same three weed plants were grown in pots and then the soil in which the weeds had been grown was leached. The leachate (drainage water) was used as a water stock for germination studies of spring wheat in petri dishes. Leachate containing water soluble root exudates, if at all present, of the three weed species demonstrated no significant effects on the total germination of spring wheat seeds in petri dishes. This occurred for all three weed species grown in both sterile and unsterile soil.
Bottom line here: The young scientist team of Jeremy Brimhall and Marshall Overcast did a great job of investigating allelopathy of wild oat, wild buckwheat, and kochia with respect to spring wheat. Their observations: something happens when kochia precedes spring wheat that reduces the performance of spring wheat. Allelopathy?