Abstract：By adding corn straw to soil with low, medium and high organic matter content and deorganic content for indoor culture experiments, the effects of straw addition on decomposition capacity and soil acidity of soil with different organic matter contents were studied. The results showed that after constant temperature incubation at 15 ℃ for 150 days, the decomposition rate of straw in the soil showed as follows: high organic matter soil treatment>medium organic matter treatment>low organic matter soil treatment>deorganic soil treatment. At different stages of straw addition, the humification coefficient of soil with high organic matter content was higher than that of the other three organic matter content soil treatments, and the organic matter conversion effect of the high organic matter con‐tent soil treatment was the best, and the organic amount increased the most. With regard to the effect of soil acidity, with the increase of straw addition, soil pH value increased, and the contents of ex‐changeable H+, exchangeable Al3+, and exchangeable acid in the soil decreased. Under different con‐ditions of straw addition, the four soil treatments with different organic matter contents showed different performances. The straw addition amount of low organic matter content soil treatment was be‐
tween 10-15 g/kg, soil pH increased the most, the contents of soil exchangeable H+, exchangeable Al3+, and exchangeable acid decreased the most, and soil acidity decreased the most. The amount of straw addition for the two treatments of medium and high organic matter content soils was between 15-20 g/kg, the maximum increase was shown in soil pH, the contents of soil exchangeability H+, exchangeable Al3+ , and exchangeable acid content decreased the most, and soil acidity decreased the most. Compared with the previous three organic matter content soil treatments, deorganic soil treatment had no obvious effect on reducing soil acidity. The content of exchangeable Al3+ in soil with different straw additions and different organic matter contents was much higher than that of exchangeable H+, which directly affected soil exchangeable acid and soil pH. Therefore, returning straw to the field can effectively reduce soil acidity and relieve soil acidification while increasing the content of soil organic matter.
