不同区域水稻土的氮素分配及δ^15N特征

Distribution and δ^(15)N Character of Nitrogen in paddy soils located in different regions

对分别位于吉林龙井、河南封丘、浙江慈溪和江西进贤4个不同区域的水稻土中氮素分配和稳定性氮同位素(δ15N)特征进行了研究。结果表明,随着样点位置的南移,相对于20-40 cm土层,水稻土表层(0-20 cm)中氮素的富集效果越来越明显。随着样点位置的南移,水稻土表层硝态氮含量与铵态氮含量的比值逐渐降低。不同区域水稻土表层中,氮素主要集中在<10μm复合体部分,<50μm复合体中氮素含量由高到低的顺序为:<2μm,2-10μm,10-50μm。不同粒级水稻土复合体中,2~10μm复合体中氮素含量和分配比例均最稳定。水热条件、耕作制度以及母土特征等会影响到水稻土表层中复合体氮素的分配特征。不同区域水稻土的剖面全氮δ15N特征不尽相同,反映了不同区域水稻土中进行的氮素转化和迁移过程之间存在差异。在0-20 cm土层中,除龙井水稻土以外,其它区域水稻土均出现明显的δ15N贫化现象。另外,不同区域的稻田表土全氮δ15N均低于旱地表土。

Abstract： Distribution and ^15N character of nitrogen in paddy soils located in different regions （Longjing ot Jilin Province, Fengqiu of Henan Province, Cixi of Zhejiang Province and Jinxian of Jiangxi Province） were studied. The results showed that paddy soils in the south tended to show more obvious enrichment effect of nitrogen in the 0--20 cm layer relative to the 20--40 cm layer than the soils in the north. Paddy soil in the south tended to have higher ratio of nitrate nitrogen content to ammonium nitrogen content in the 0--20 cm layer than the soils in the north. In the 0--20 cm of paddy soils located in different regions, total nitrogen of paddy soils was mostly concentrated in organo-mineral complexes of .〈10 μm, and total nitrogen content in different particle-sizes complexes of 〈50 μm was lined in a deereasing order： 〈2 μm, 2-10 μm, 10-50μm. Among different particle-sizes complexes, total nitrogen content and total nitrogen abundanee in eom- plex of 2-10μm were the most stable. Hydrothermal conditions, farming system and the characteristics of original soil could influence the distribution of total nitrogen in eomplexes of topsoil in paddy soil. The 15N character of total nitrogen was different in profiles of paddy soils located in different regions, and the phenomenon showed that transformation and migration of nitrogen was different in paddy soils loeated in different regions. ^15N-depleted topsoil existed in paddy soil profiles located in different regions except Longjing. In addition, the δ^15N value of total nitrogen was lower in topsoil of paddy fields than uplands.