摘要:为探究稻虾种养模式冬春季节合理的秸秆还田方式，本研究以秸秆还田配施氮肥调节C/N为切入点，在2017年12月—2018年5月通过田间试验，设秸秆不还田不施氮肥（对照，CK）、秸秆还田C/N为35（S）、秸秆还田配施氮肥C/N为25（SN1）、秸秆还田配施氮肥C/N为15（SN2）以及单施氮肥处理（N1）。探讨秸秆还田不同C/N对冬春季稻虾田养殖水体、土壤养分及酶活性的影响。结果表明：1）CK处理后期的水体总磷含量最低，各处理水体总氮含量在还田前期变化幅度不大；不同处理水体铵态氮含量低于克氏原螯虾安全耐受限度。2）秸秆还田后，SN2处理显著增加了土壤有机质含量，同时土壤硝态氮含量较还田前增加240%；秸秆还田降低了土壤容重，SN2处理组容重最低。3）N1和SN2处理提高了土壤多酚氧化酶活性，其中SN2处理组酶活性最高。在3种秸秆还田处理中，SN2处理土壤脲酶活性高于其他处理，N1处理前期表现出较高酶活性，后期开始降低。综上，秸秆还田配施氮肥调节C/N为15在稻虾田土壤养分含量、酶活性等方面优于其他处理。
Abstract:The integrated rice-crayfish breeding model is an ecological agriculture model that combines paddy field plantation and crayfish (Procambarus clakii) cultivation. This model both guarantees food production and increases economic benefits. At present, research relating to this model is focused on the efficiency of crayfish culture technology, while information regarding straw resource utilization under this model has not been reported. Rice straw is rich in nitrogen, phosphorus, and potassium. However, if improperly handled and directly immersed in water, its degradation process will cause deterioration of water quality and pollution of soil. Therefore, returning straw to the field not only effectively uses resources, but also avoids the risks caused by random straw disposal. In order to explore the optimal model for returning straw during winter and spring (when crayfish are breeding), we carried out a field experiment to study the effects of different C/N ratios of straw returning on cultured water, soil nutrients, and enzyme activity in Dec. 2017 to May 2018. The experiment consisted of five treatments: straw removal without fertilizer (CK), straw returned without N fertilizer (C/N ratio of 35:1, S), straw returned with N fertilizer (adjusted C/N ratio of 25:1, SN1), straw returned with N fertilizer (adjusted C/N ratio of 15:1, SN2), and N fertilizer without straw returned (N1). The results showed that total phosphorus (TP) content was the lowest in the CK treatment at the later stage of straw returning period. The total N content in each period was the lowest in CK treatment, followed by SN2 treatment. The ammonia nitrogen (NH4-) content in the treated water was lower than the safe tolerance limit of the crayfish. Additionally, the soil organic matter content increased under straw returning; the most significant result was obtained in SN2 treatment, with an increase of 56.1% compared to before the field experiment. Soil nitrate nitrogen (NO3-) content in SN2 treatment increased by 240% compared to that before straw returning. Returning straw reduced bulk density of soil. The SN2 treatment recorded the lowest bulk density overall. Finally, we found that N1 and SN2 treatments could increase soil polyphenol oxidase activity; activity was highest in SN2 treatment group. Among three straw returning treatments, soil urease activity in SN2 treatment was lower than that in other treatments only in the first month after returning to the field. N1 treatment showed higher enzyme activity in the early experimental stage and began to decrease in the later stage. Overall, the results suggest that an optimal C/N ratio for returning straw with N fertilizer was 15:1, in terms of soil nutrient content and enzyme activity.
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