The study looked at how adding organic materials like green manure and wheat straw to paddy soils affects soil nitrogen levels and rice yield. They found that adding high C/N materials increased soil nitrogen when no synthetic nitrogen was used. Decomposed green manure improved soil nitrogen supply at a certain synthetic nitrogen rate. Returning green manure and wheat straw to soil had a bigger impact when synthetic nitrogen was also used. Overall, rice yield increased when both organic and synthetic nitrogen were applied together.