有机肥C/N优化下氮肥运筹对烟株根际无机氮和酶活性的影响

大田条件下研究了基于有机肥C/N优化下不同氮肥用量和基追比对烤烟根际土壤无机氮、碳氮转化及酶活性的影响。结果表明:(1)低、中氮(48.0、108.0 kg/hm²)条件下,根际NH₄⁺-N含量随生育期延长而降低;高氮(168.0 kg/hm²)条件下,根际NH₄⁺-N含量在团棵期至旺长期增加,随后降低;不同处理根际硝态氮含量均随着生育期的延长而降低;(2)土壤微生物量碳随生育期的延长和施氮量的增加而增加;(3)土壤脲酶和转化酶活性均随施氮水平增加而增强,低氮和中氮条件下脲酶活性在成熟期时略微下降,而高氮条件下土壤脲酶活性在整个生育期持续增加。低氮基追比(5:5)处理的土壤转化酶活性在团棵期后高于中高氮基追比处理。高氮水平因施氮量过大促使土壤有效氮持续供应,致使成熟期不能及时"氮素调亏",降低烟叶品质;而中氮水平各处理的土壤脲酶活性呈先增加后降低趋势,并以氮肥适当后移,基追比(5:5)时烟株"旺长-现蕾"阶段土壤酶活性较高,与该阶段烟株氮素需求规律相吻合。

The Effect of Nitrogen Management on Nmin and Enzyme Activities in Rhizosphere Soil of Flue-cured Tobacco under the Optimization of C/N with Organic Fertilizer

A field experiment was carried out to study the effect of nitrogen management on soil Nmin, soil carbon and the enzyme activities in tobacco rhizosphere under the optimization of C/N with organic fertilizers. The results showed that:(1) In the lower nitrogen treatments N1 and N2, NH₄⁺-N contents in the rhizosphere soil decreased during the growth season while in the higher nitrogen N3 treatment, NH₄⁺-N content increased at the rosette to vigorous growth stage, then decreased,.and nitrate nitrogen decreased for all treatments; (2) The microbial carbon and nitrogen increased with the nitrogen level and the growth process. (3) The soil urease and invertase activities increased with the nitrogen level, the soil urease activities were slightly reduced in the lower N1 and N2 treatments at the mature stage, whereas that of the higher N3 treatment increased during the whole growth period; The soil invertase activities were higher at the rosette stage in the S1 and S2 treatments, while it was higher after the rosette stage in S3 treatment. In the higher nitrogen level treatment (N3), soil nitrogen was continuously excessively supplied, and nitrogen was not reduced to the "nitrogen deficit" level during the mature period, which led to reduced tobacco quality; while at the N2 level, the soil urease activities of the S3 treatment increased first then decreased, which was more consistent with the nitrogen demand of the plants.