The study looked at how different timing and amounts of nitrogen fertilizer affect rice yield and nitrogen efficiency when straw is returned to the fields. They found that splitting the nitrogen fertilizer application into two parts, with the second part given earlier during the growing season, led to high rice yields and nitrogen efficiency. This method maintained similar yields to more frequent nitrogen applications while using less fertilizer. Overall, applying nitrogen fertilizer in two splits with straw returning can help farmers achieve high rice yields and efficient use of nitrogen.