A study looked at how tobacco plants absorb and use nitrogen from fertilizer made of rape straw. They used a special tracing method to track the nitrogen. The results showed that tobacco plants absorbed less nitrogen from the straw fertilizer compared to other sources. The amount of nitrogen used varied in different parts of the plant and at different stages of growth. Adding more rape straw fertilizer increased nitrogen absorption by the tobacco plants. Using a specific ratio of rape straw fertilizer helped the plants use nitrogen efficiently without leaving too much in the soil. However, using too much fertilizer decreased nitrogen absorption by the plants and left more in the soil. Mixing different types of fertilizer affected how the plants absorbed nitrogen in different parts of the plant.