A study was done in a red clay soil area to see how nitrogen behaves when chemical fertilizer and manure are used in double rice farming. They found that ammonia nitrogen is the main form of nitrogen in the soil. After applying fertilizer, nitrogen levels peaked in surface water within a few days and in soil within a few days to a week. Using manure with fertilizer led to lower nitrogen levels in water and soil compared to just using fertilizer. The combined manure and fertilizer treatment also increased rice yield and soil organic matter more than just using fertilizer. This method can help reduce the negative impact of excessive chemical nitrogen on the environment.