秸秆对尿素氮在土壤中转化的影响

Effect of Straw on Urea Nitrogen Transformation in Soil

秸秆还田对提高土壤肥力具有重要意义,但是秸秆还田对氮素在土壤中的转化过程的影响还不清楚。通过室内培养研究了等量施氮条件下不同秸秆还田量对尿素态氮的水解、硝化及反硝化等氮素转化过程的影响。试验设5个处理,分别为CK,不加尿素氮不加秸秆;S0,尿素氮200 mg·kg^(−1)+秸秆量0 g·kg^(−1);S1,尿素氮200 mg·kg^(−1)+秸秆量4.44 g·kg^(−1);S2,尿素氮200 mg·kg^(−1)+秸秆量8.88 g·kg^(−1);S3,尿素氮200 mg·kg^(−1)+秸秆量13.33 g·kg^(−1)。结果表明,秸秆添加可促进尿素水解过程,24 h后,尿素的水解率从S0处理的71.9%增加至S3处理的98.0%。添加秸秆在前15天会减少土壤中铵态氮的含量,与S0相比,第3天时,S1、S2、S3的铵态氮含量分别减少了18.35%、27.09%、25.47%。S0处理和S1处理土壤中的硝态氮含量均随着培养时间的延长而升高,且在培养的第21天基本达到稳定;而S2和S3处理的硝态氮含量则呈先下降后上升的趋势。从培养3 d起添加秸秆的处理土壤中的硝态氮含量始终低于不添加秸秆的处理(P<0.05),且随着秸秆用量的增加土壤中的硝态氮含量显著降低(P<0.05)。添加秸秆增加了氮肥的反硝化损失,且随着秸秆用量的增加,反硝化损失率急剧增加,从S0处理的0.45%增加至S3处理的62.87%。添加秸秆处理土壤的微生物量碳(SMBC)含量和空白对照相比,均有明显的提升(P<0.05),且随着秸秆用量的增加而增加。研究表明,秸秆的添加能提高SMBC的含量,进而增加了土壤氮素的同化,但同时也增加了氮素的反硝化损失,且随秸秆添加量的增大,影响效果越明显。

In this experiment,the effects of different amounts of straw returned to the field on the hydrolysis,nitrification and denitrification of urea nitrogen under the condition of equal nitrogen application were studied through indoor cultivation.Five treatments were set up in the experiment,CK,no urea nitrogen and no straw;S0:Urea nitrogen 200 mg·kg^(−1)+straw amount 0 g·kg^(−1);S1:Urea nitrogen 200 mg·kg^(−1)+straw amount 4.44 g·kg^(−1);S2:Urea nitrogen 200 mg·kg^(−1)+straw amount 8.88 g·kg^(−1);S3:Urea nitrogen 200 mg·kg^(−1)+straw amount 13.33 g·kg^(−1).The results showed that straw addition could promote the hydrolysis process of urea.After 24 h,the hydrolysis rate of urea increased from 71.9%in S0 treatment to 98.0%in S3 treatment.The addition of straw could reduce the content of ammonium nitrogen in soil in the first 15 days.Compared with S0,the content of ammonium nitrogen in S1,S2 and S3 was reduced by 18.35%,27.09%and 25.47%on the third day,respectively.The nitrate nitrogen content in soil of S0 treatment and S1 treatment both increased with the extension of incubation time,and basically reached stability on the 21st day of cultivation;while the nitrate nitrogen content of S2 and S3 treatment showed a trend of decreasing first and then increasing.After 3 days of culture,the nitrate nitrogen content of the treatment with straw was always lower than that without straw(P<0.05),and the nitrate nitrogen content in soil was significantly decreased with the increase of straw dosage(P<0.05).The addition of straw increased the denitrification loss of nitrogen fertilizer,and with the increase of the amount of straw,the denitrification loss rate increased sharply,from 0.45%in S0 treatment to 62.87%in S3 treatment.Compared with the blank control,the microbial biomass carbon(SMBC)content of the soil treated by adding straw was significantly increased(P<0.05),and it increased with the increase of the amount of straw.The results showed that the addition of straw could increase the content of SMBC,thus increasing the assimilation of soil nitrogen,but at the same time,it also increased the denitrification loss of nitrogen,and with the increase of the amount of straw addition,the effect was more obvious.