Rice straw added to fields in winter increases rice yield and soil potassium levels compared to adding it in spring. When no nitrogen fertilizer is used, early rice yield is higher with winter straw incorporation. With nitrogen fertilizer, yield increases by 12.3% in 2009 and 23.8% in 2011. Winter straw incorporation boosts soil potassium content, especially with nitrogen fertilizer, increasing available potassium by 29.6% to 26.0% before planting from 2009 to 2011. Winter straw incorporation is better than spring incorporation for rice field management.