The researchers studied how different pH levels and nitrogen amounts affect the soil's ability to resist acidification in paddy fields. They added calcium carbonate and sulfuric acid to the soil and tested it with various pH levels and nitrogen doses. The results showed that the soil's buffer capacity decreased with higher nitrogen levels and lower pH levels. The presence of certain cations in the soil played a crucial role in maintaining its buffer system. Changes in pH and buffer capacity were mainly observed in the top 20 cm of soil under different pH levels, while nitrogen application affected the soil up to 40 cm deep.