氮肥管理和秸秆腐熟剂对^(15)N标记玉米秸秆氮有效性与去向的影响

Bioavailability and Fate of Nitrogen from ^(15)N-labeled Corn Straw as Affected by Nitrogen Management and Straw Microbial Inoculants

【目的】研究氮肥用量、有机无机配合和添加秸秆腐熟剂对秸秆氮当季有效性、后效及去向的影响,为桔秆还田条件下的氮肥管理提供理论依据【方法】运用^(15)N同位素示踪技术,采用盆栽试验连续种植一季冬小麦和两茬玉米,研究^(15N)标记玉米秸秆(^(15)N-秸秆)氮的生物有效性和对土壤氮库的贡献试验推荐施氮量210kg N·hm^(-2),约0.1 g N·kg-1土,桔秆粉碎后按3.0 g·kg^(-1)土掺入每盆中设4个氮水平:不施氮;100%化肥氮;80%化肥氮;有机无机配施(80%化肥氮+20%腐熟猪粪氮)。各施氮水平下设添加和不添加桔秆腐熟剂2种情况,腐熟剂用量为0.1 g·kg^(-1)土。【结果】冬小麦吸氮量来自^(15)N-秸秆氮的比例(%Ndfs)为6.30%-14.25%,施氮比不施氮减少%Ndfs,有机无机配施比单施氨肥提高%Ndfs,添加腐熟剂不影响冬小麦的%Ndfs。第一茬和第二茬玉米吸收氮的%Ndfs分别为1.13%-3.73%和1.67%-5.97%,不施氮高于施氮处理,施氮处理间无显著差异,添加腐熟剂降低%Ndfs冬小麦对^(15)N-桔秆氮的当季利用率为7.14%-10.2%。第一茬玉米和第二茬玉米对残留^(15)N-桔秆的利用率分别为3.75%-5.51%和2.28%-3.18%。三茬后作物对^(15)N-桔秆氮的利用率为13.13%-18.60%,土壤残留率55.63%-69.16%,损失率17.26%-26.09%。三茬中施氮比不施氮提高^(15)N-秸秆氮的利用率,不同氮肥管理不影响当季利用率和第二茬后效,氮肥减量(80%推荐氮)降低^(15)N-桔秆氮第一茬后效和总利用率,但若配施有机肥则提高利用率添加腐熟剂提高^(15)N-秸秆氮当季、第一茬玉米和三茬总利用率,降残留率和损失率。冬小麦和两茬玉米收获后土壤矿质氮和微生物量氮含量变化较大,但其来源于^(15)N-桔秆氮的比例都小于3%,施氮处理的影响不明显,而添加腐熟剂增加冬小麦和第一茬玉米收获后土壤矿质氟%Ndfs,减少土壤微生物量氮%Ndfs,不影响第二茬玉米收获后土壤矿质氮和微生物量氮%Ndfs。三茬收获后残留的^(15)N-桔秆氮中矿质氮和微生物量氮也小于3%,说明残留在土壤中的^(15)N-桔秆氮主要以有机态氮存在【结论】在秸秆还田条件下。

【Objective】The purpose of this study was to demonstrate the effect of rate of nitrogen fertilization, fertilizer N combined with manure N and straw microbial inoculants on the transformation and bioavailability of nitrogen （N） from crop straw for providing scientific information and guidelines on N management under straw returning conditions. 【Method】Pot experiments were carried out using 15N isotope techniques by continuously planting one season of winter wheat and two seasons of corn to study N availability from 15N labeled corn straw （15N-straw） and its contribution to plant and soil. The recommended N rate was 210 kg N·hm^-2, equivalent to 0.1 g N·kg^-1 soil. The crushed straw was incorporated into each pot at the rate of 3.0 g·kg^-1 soil. There were four N levels： control without N （CK）, 100% fertilizer N, 80% fertilizer N and 80% fertilizer N plus 20% manure N. Each above treatment had two levels of microbial inoculants： 0 and 0.1 g·kg^-1 soil. A total of eight treatments with four replications for each were designed. 【Result】The percentage of N derived from 15N-straw （%Ndfs） in winter wheat plant was 6.30% to 14.25%, reduced by N application compared with CK. Combination of fertilizer N and manure N resulted in higher winter wheat %Ndfs than fertilizer N alone. Addition of microbial inoculants did not significantly influence winter wheat %Ndfs compared with treatments without microbial inoculants. The %Ndfs in the following 1st and 2nd corn plant was, respectively, 1.13% to 3.73% and 1.67% to 5.97%, reduced by N application but no difference existed between N treatments. Addition of microbial inoculants reduced corn plant %Ndfs from residual 15N-straw. Recovery of 15N （REN） from ^15N-straw by winter wheat was 7.14% to 10.32%, while the residual REN from ^15N-straw by the 1st and 2nd following corn was 3.75% to 5.51% and 2.28% to 3.18%, respectively. Total of 13.13% to 18.60% of 15N-straw N was recovered, 55.63% to 69.16% remained in soil and 17.26% to 26.09% lost after three times of cropping. N application increased REN compared with CK. N management did not influence REN from 15N-straw by winter wheat and the 2nd corn, but 80% recommended fertilizer N decreased REN by the 1st corn and three crops, while increased when applied with manure. Addition of microbial inoculants significantly improved REN from 15N-straw by winter wheat and the 1st season corn and total of three cropping, reduced residual and loss of N from ^15N-straw. The content of mineral N （Nmin） and microbial biomass N （MBN） after crop harvests varied greatly, but the %Ndfs in Nmin and MBN was all less than 3% which was not greatly influenced by N fertilizer management. While, addition of microbial inoculants increased %Ndfs in soil Nmin as well as decreased %Ndfs in soil MBN after winter wheat and 1st corn,but no effect after 2nd corn. The percentage of remained ^15N-straw in Nmin and MBN after three crops was less than 3%, suggesting that the remained 15N-straw N in soil after three cropping was in organic form. 【Conclusion】Combination of chemical fertilizer N with manure N and addition of microbial inoculants is the recommended practice to increase N availability of straw under the conditions of straw returning to field.