有机无机氮配施对不同程度盐渍土硝化和反硝化作用的影响

Effects of Combination of Organic and Inorganic Nitrogen on Nitrification and Denitrification in Two Salinized Soils

以内蒙古河套灌区轻度盐渍土S_(1)(EC=0.62 dS·m^(-1))及中度盐渍土S_(2)(EC=1.17 dS·m^(-1))为对象,研究硝化和反硝化进程对盐渍化程度和有机无机氮配施比例的响应及其影响因素.本试验设置了6个处理,包括不施氮(CK)、单施无机氮(U1)以及用有机氮(U3O1、U1O1、U1O3和O1)替代25%、50%、75%和100%的无机氮.结果表明,盐度升高会降低土壤硝化势而提高土壤反硝化能力,同一处理S_(1)土壤硝化潜势较S_(2)土壤高出28.81%~69.67%,而反硝化能力降低17.16%~88.91%.盐度升高会降低AOB丰度及硝化贡献率,但会增加AOA丰度和硝化贡献率;盐度增加会提高土壤nirK和nirS型菌丰度,同时会增加N_(2)O/(N_(2)O+N2)产物比,但会抑制nosZ丰度.S_(1)土壤,以U1O1处理硝化势和反硝化能力最大,较单施化肥增幅分别达到18.59%和15.87%;S_(2)土壤,各施肥处理之间土壤硝化势差异不显著,反硝化能力以O1处理最大,较单施化肥提高88.26%.S_(1)和S_(2)盐渍土分别以U1O1及O1处理获得较高的AOB基因丰度及硝化贡献率,且增大了nirS和nosZ基因丰度,并显著降低N_(2)O/(N_(2)O+N2)产物比.综上,相比单施无机氮,轻度盐渍土以有机无机氮各半配施,中度盐渍土以单施有机氮更加利于土壤硝化反硝化过程进行.

Focusing on typical mildly saline soil,S_(1)(EC,0.62 dS·m^(-1)),and moderately saline soil,S_(1)(EC,1.17 dS·m^(-1)),in Hetao Irrigation District of Inner Mongolia,the response of nitrification and denitrification process to salinization degree and the proportion of organic and inorganic nitrogen application were studied.The experimental treatments consisted of(1)no nitrogen(CK),(2)only inorganic nitrogen(U1),and(3)organic nitrogen(U3 O1,U1 O1,U1 O3,and O1)compared to 25%,50%,75%,and 100%inorganic nitrogen.The results showed that increasing salinity reduced the soil nitrification potential and increased the soil denitrification capacity.The soil nitrification potential of the S_(1)soil was 28.81%-69.67%higher than that of the S_(2)soil,while the denitrification capacity was reduced by 17.16%-88.91%.With an increase in salinity,the AOB abundance and nitrification contribution rate were reduced,but the AOA abundance and nitrification contribution rate were increased.Furthermore,an increase in salinity increased the abundance of nirK and nirS bacteria,and increased N2 O/(N2 O+N2)production,but reduced the abundance of nosZ.In the S_(1)soil,the nitrification potential and denitrification capacity of U1 O1 were highest,increasing by as much as 18.59%and 15.87%,respectively,compared to the U1 treatment.In the S_(2)soil,the difference in the soil nitrification potential between the various fertilization treatments was not significant,and the denitrification capacity of the O1 treatment was highest.The S_(1)and S_(2)saline soils treated with U1 O1 and O1,respectively,had higher AOB gene abundance and nitrification contribution rates,increased nirS and nosZ gene abundances,and significantly reduced N2 O/(N2 O+N2)product ratios.Our findings suggested that mildly saline soils(120 kg·hm-2 urea+120 kg·hm-2 organic fertilizer)and moderately saline soils(240 kg·hm-2 organic fertilizer)are more conducive to soil nitrification and denitrification processes compared to soils to which inorganic nitrogen is applied alone.