杭嘉湖平原典型稻田土壤活性铁与氮素赋存的关系

Relationship between Active Iron and Nitrogen in Typical Paddy Soils from Hangjiahu Plain

稻田土壤中铁的氧化还原过程与氮素的固定及损失关系密切,为更好地了解活性铁与氮素赋存的数量关系,采集杭嘉湖平原萧山、余杭、长兴、桐乡、平湖等地典型稻田土壤样品,通过分析水稻土中活性铁及不同赋存形态氮素的含量,探究稻田土壤氮库与活性铁及其他理化因子的数量关系,以期为稻田土壤氮素科学管理提供依据.结果表明,5地稻田土壤以桐乡与长兴水稻土中Fe(Ⅱ)含量最高,Fe(Ⅲ)及络合铁含量在余杭水稻土中高于其他样点土壤,而平湖稻田土中3种活性铁含量均最低.平湖样点土壤总氮及铵态氮含量低于其他样点,而硝态氮、亚硝态氮存留量最高;长兴与桐乡样点稻田土中铵态氮含量较高,但硝态氮存留量较低.5地土壤中总氮、铵态氮及硝态氮与各基本理化性质之间无相关关系,但硝态氮与3种活性铁成分均呈现显著的负相关性,铵态氮、总氮含量则与Fe(Ⅱ)显著正相关,说明活性铁影响稻田土壤中不同形态氮素的存留量.逐步线性回归分析结果进一步表明,稻田土中不同形态氮含量受活性铁及氧化还原电位、有机质、pH等关键理化性质的协同控制.

The redox process of iron in paddy soil is closely related to nitrogen fixation and loss.In order to have a better understanding on the quantitative relationship between active iron and nitrogen,paddy soil samples were collected in 5 sites from Hangjiahu Plain,which were Xiaoshan,Yuhang,Changxing,Tongxiang and Pinghu.The results showed that the soil properties were significant different in paddy fields of five sites.The paddy soils of Tongxiang and Changxing had the highest contents of Fe(Ⅱ).The soil contents of Fe(Ⅲ)and chelated Fe in Yuhang site were higher than other sites.However,three fractions of active iron in Pinghu paddy soil showed the lowest concentrations.The amounts of total nitrogen and ammonium nitrogen in Pinghu were also lower than other sites,while nitrate and nitrite nitrogen showed the highest level.The contents of ammonium nitrogen in paddy soils of Changxing and Tongxiang were higher,but the retention of nitrate nitrogen in soils were lower.No significant correlations were observed between physicochemical properties and total,ammonium or nitrate nitrogen in five paddy soils,but the significant negative correlations were observed between nitrate nitrogen and three active iron components,respectively.Furthermore,ammonium and total nitrogen contents were also significantly positively related to Fe(Ⅱ),indicating that active iron affected the retention forms of nitrogen in paddy soil.According to the results of stepwise linear regression analysis,the regression curves of different nitrogen retention in the paddy soil showed the more significant levels after cooperation of active iron and other key physicochemical properties(Eh,OM,pH,etc.).