Fababeans are a long season crop (planted in May and harvested in October) and produce a lot of residue that is left behind when the grains are removed by combining. After combining, the farmer rotovated the residues into the soil. We surmised that as the residues are incorporated late in the year, there is not much decomposition over the winter. In the spring there would be very active decomposition and consumption of oxygen as the residues decompose, pockets in the soil go anaerobic and organic acids such as lactic acid accumulate for a period. When oats are planted in such soil, germination &/or early root growth is inhibited by the organic acids and oats get off to a poor start. Weeds keep on germinating and soon take over the crop.