有机酸积累和毒害是稻田秸秆还田中受到广泛关注的问题。本文以水稻与小麦秸秆为材料,采用淹水培养研究了甲酸、乙酸、丙酸及丁酸在土壤中的积累及其与秸秆碳氮比、氮肥添加量的关系。结果表明,在不施用氮肥的情况下,随秸秆用量的增加,秸秆处理的有机酸积累均显著增多。与稻秸处理相比,麦秸处理的有机酸(尤其是丙酸)积累量显著较高,土壤溶液中NH4+浓度显著较低。加入尿素明显减少有机酸积累,促进CH4排放,但对CO2的排放无显著影响;氮素的影响在麦秸处理中表现的尤为明显。上述结果说明麦秸的高碳氮比增加了无机氮的生物固定,抑制有机酸向CH4转化,从而导致麦秸处理有机酸积累量高于稻秸处理。施用氮肥是减少麦秸还田后有机酸积累的有效措施之一,但此措施将可能促进CH4的排放。 Accumulation of organic acids and poisoning are the problems that have attracted much attention in the field of paddy straw. In this paper, rice and wheat straw were used as materials to study the accumulation of formic acid, acetic acid, propionic acid and butyric acid in soil and its relationship with the carbon and nitrogen ratio of straw and nitrogenous fertilizer. The results showed that with the increase of the amount of straw, the accumulation of organic acids in straw treatment increased significantly without applying nitrogen fertilizer. Compared with rice straw treatment, the accumulation of organic acids (especially propionic acid) in wheat straw was significantly higher, and the concentration of NH4 + in soil solution was significantly lower. Addition of urea significantly reduced the accumulation of organic acids and promoted the emission of CH4, but had no significant effect on the emission of CO2. The effect of nitrogen on wheat straw was especially evident. The above results indicate that the high C / N ratio of wheat straw increases the biological fixation of inorganic nitrogen and inhibits the conversion of organic acids to CH4, resulting in higher accumulation of organic acids in wheat straw than in straw. Application of nitrogen fertilizer is one of the effective measures to reduce the accumulation of organic acids after wheat straw is returned to the field. However, this measure will probably promote the emission of CH4.