氮肥用量优化对甜玉米氮肥吸收利用率及氮循环微生物功能基因的影响

Effects of nitrogen fertilizer dosage optimization on nitrogen uptake content and utilization efficiency and microbial function genes of nitrogen cycle in sweet corn

【目的】研究氮肥用量优化对甜玉米氮肥利用率及根际土壤氮循环微生物功能基因的影响,为农业生产中氮肥减施及高效利用提供参考。【方法】在磷、钾肥用量优化一致的基础上,设3个施氮水平:(1)对照,不施氮;(2)常规施氮水平,氮用量420 kg/ha;(3)优化施氮水平,氮用量330 kg/ha。玉米成熟期采集植株样品及土壤样品,采用常规分析、根际土壤高通量测序和功能基因芯片(GeoChip 5.0)技术,对不同氮肥用量处理甜玉米产量、可溶性糖含量、土壤氮肥利用率、细菌群落结构及氮循环功能基因进行分析。【结果】与对照相比,优化施氮水平与常规施氮水平均能显著提高甜玉米鲜苞产量(P<0.05,下同),但二者间无显著差异(P>0.05,下同),优化施氮水平的可溶性糖含量最高(122.2 mg/kg),显著高于常规施氮水平(113.8 mg/kg),氮肥吸收利用率和氮肥偏生产力也分别较常规施氮水平处理提高8.5%(绝对值)和7.7 kg/kg。9个土壤样品16S rRNA高通量测序共检测到144736个OTUs,分属于46门106纲213目289科404属。优化施氮水平与氮循环相关的固氮菌属Rhodanobacter和Bradyrhizobium的相对丰度高于常规施氮水平,而氨氧化细菌Bryobacter和硝化作用细菌Candidatus_Nitrocosmicus的相对丰度则低于常规施氮水平。采用GeoChip 5.0技术在9个土壤样品中共发现了2752个氮循环基因,分属于8个亚类功能。其中固氮、氨化、硝化、同化氮还原、氮同化和异化氮还原等作用表现为优化施氮水平高于常规施氮水平,除固氮作用外,两个处理间差异显著;氨氧化作用表现为常规施氮水平高于优化施氮水平,但两个处理间差异不显著。【结论】氮肥用量优化有助于调控参与氮循环关键环节的细菌菌属丰度,促进氮循环微生物功能基因的固氮作用和氨化作用,提高土壤氮肥吸收利用率和甜玉米可溶性糖含量,且甜玉米鲜苞产量与常规施氮水平相当,在氮肥减量增效的同时达到甜玉米稳产提质的效果,可作为推荐施肥方式进行推广应用。

【Objective】To study the effects of nitrogen fertilizer application optimization on nitrogen fertilizer utilization efficiency and microbial functional genes of nitrogen cycle in rhizosphere soil of sweet corn,and to provide reference for nitrogen fertilizer reduction and efficient utilization in agricultural production.【Method】The optimized dosages of phosphorus and potash fertilizer were the same,three nitrogen application levels were set in this experiment:(1)control,no nitrogen application;(2)conventional nitrogen application level,nitrogen dosage 420 kg/ha;(3)the nitrogen application level was optimized,and the nitrogen dosage was 330 kg/ha.Plant samples and soil samples were collected during maize maturity.The yield,soluble sugar content,soil nitrogen utilization efficiency,bacterial community structure and nitrogen cycle function genes of sweet corn treated with different nitrogen fertilizer dosages were analyzed by conventional sweet corn index analysis,high throughput sequencing of rhizosphere soil and GeoChip 5.0 technology.【Result】Compared with the control,the results of this study showed that both optimized and conventional nitrogen levels could significantly increase the fresh ear yield of sweet corn(P<0.05,the same below),there was no significant difference between the fresh ear yield of sweet corn treated with optimized nitrogen application level and that treated with conventional nitrogen application level(P>0.05,the same below).The soluble sugar content was the highest in the treatment with optimized nitrogen application level(122.2 mg/kg)which was significantly higher than the conventional nitrogen application level(113.8 mg/kg).The results showed that the nitrogen recovery efficiency and nitrogen partial productivity were increased by 8.5%(absolute value)and 7.7 kg/kg.At the same time,144736 OTUs were detected after 16S rRNA high-throughput sequencing was performed on 9 soil samples,which belonged to 404 genera,289 families,213 orders,106 classes and 46 phylum.The results of relative abundance of Rhodanobacter and Bradyrhizobium were higher than that of conventional nitrogen application,while the results of relative abundance of Bryobacter and Candidatus_Nitrocosmicus were lower than that of conventional nitrogen application.A total of 2752 nitrogen cycle genes were found in 9 soil samples using GeoChip 5.0 technology,and the functions of these genes were divided into 8 subclasses.The effects of nitrogen fixation,ammoniation,nitrification,nitrogen assimilation reduction,nitrogen assimilation and nitrogen alienation reduction on nitrogen substances were shown as that the optimized nitrogen application level treatment was higher than the conventional nitrogen application level treatment.Except biological nitrogen fixation,the difference between the two treatment groups was significant.The effect of ammonia oxidation mainly showed that the conventional nitrogen application level treatment was higher than the optimized nitrogen application level treatment,but the difference between the two treatment groups was not significant.【Conclusion】The improvement of the amount of nitrogen fertilizer used in crops can help regulate the bacterial species abundance of crops that participate in the key link of the nitrogen cycle,so as to promote the nitrogen fixation and ammoniation of microbial functional genes in the nitrogen cycle,ultimately improve the uptake and utilization rate of nitrogen fertilizer in plant soil and soluble sugar content of sweet corn,and the fresh ear yield of sweet corn is equivalent to that of conventional nitrogen application level,which can achieve the effect of stable yield and quality improvement of sweet corn while reducing nitrogen fertilizer and increasing efficiency.This treatment can be promoted as a recommended fertilization mode.