1. The root injury of soy-bean sown under paddy field conditions was observed. 2. When soy-bean was planted alone, the root was serverely injured and it could not generally survive. When it was planted with paddy rice, the root injury was slight. 3. It is presumed that when the two were planted in the same paddy field, the respiration of soy-bean root benefited from the high oxidizing power of paddy rice root.