Returning 100% of crop straw to the soil can boost soil fertility and increase wheat and rice yields over time. Decomposing wheat and rape straws release important nutrients like nitrogen, phosphorus, and potassium into the soil. This practice also helps store more organic carbon in the soil and reduces runoff. However, it can lead to increased emissions of methane, ammonia, and nutrient loss through leaching. To balance the benefits and drawbacks, it's recommended to adjust nitrogen fertilization levels during the growing season, reduce phosphorus and potassium fertilization, and apply straw during dry periods for rice cultivation.