聚合氨基酸对北方水稻土中氧化铁存在形态的影响

为了解不同类型水稻土中氧化铁含量特征,探明添加外源聚合氨基酸对水稻土中氧化铁形态变化的影响,本研究以中国北方不同类型水稻土(棕壤型、草甸土型和滨海盐渍型)为研究对象,设置添加占供试土壤干重0.05%的γ-聚谷氨酸和聚天冬氨酸处理,以不添加氨基酸作为对照。通过室内恒温厌氧培养30 d后,测定各水稻土全铁、游离氧化铁、无定形氧化铁和络合态铁含量及氧化铁的活化和络合程度。结果表明:供试的北方3种典型水稻土中,游离氧化铁含量为滨海盐渍型草甸土型≥棕壤型,络合态铁含量为棕壤型滨海盐渍型≥草甸土型,而无定形氧化铁含量为棕壤型滨海盐渍型草甸土型。两种外源聚合氨基酸对不同类型水稻土氧化铁形态转化能力影响存在差异,与不添加氨基酸的对照相比,添加γ-聚谷氨酸的棕壤型水稻土无定形氧化铁和络合态铁含量分别增加27.72%和32.25%,聚天冬氨酸对无定形氧化铁和络合态铁含量无显著促进作用;在草甸土型水稻土中,γ-聚谷氨酸和聚天冬氨酸均能显著增加无定形氧化铁含量,且与对照相比,络合态铁含量分别增加136.24%和12.00%;γ-聚谷氨酸能有效促进滨海盐渍型水稻土中无定形氧化铁和络合态铁的生成。总之,添加γ-聚谷氨酸和聚天冬氨酸对水稻土游离氧化铁的含量没有明显影响;而添加γ-聚谷氨酸能有效增加水稻土中无定形氧化铁和络合态铁含量,降低晶胶率,有利于提高土壤中有效铁含量,显著活化铁氧化物,抑制各类型水稻土中铁的结晶老化;而聚天冬氨酸对水稻土无定形氧化铁和络合态铁没有明显的激发效应。

Effect of aggregated amino acid on the form of iron oxide in paddy soils in North China

The purpose of this study is to characterize the amount of iron oxide in different types of paddy soil and investigate the effect of exogenous polymeric amino acids on their forms transformation. Different types of paddy soil (brown soil, meadow soil and littoral saline soil) in North China were chosen as the research object. An incubation experiment was carried out by addingγ-poly-glutamic acid and poly aspartic acid, according to 0.05% of dry soil weight to these three paddy soils. After constant temperature and anaerobic incubation for 30 days, the content of total iron oxide (TFe), free iron oxide (DFe), amorphous iron oxide (OFe) and complexed iron oxide (CFe) were measured, and the activation and complexing degree of iron oxide were calculated in three paddy soils. Simultaneously, no addition of amino acids was set as the control. The results showed that (1) the content of free iron oxide in three typical paddy soils from high to low was: littoral saline soil > meadow soil≥ brown soil; the sequence of complex iron oxide content was brown soil > littoral saline soil≥ meadow soil; and the sequence of amorphous iron oxide was brown soil > littoral saline soil > meadow soil. (2) The content of amorphous iron oxide and complexed iron oxide increased by 27.72% and 32.25%, respectively, in paddy soil derived from brown soil withγ- poly-glutamic acid application compared with that of control; but there was no significant change for those adding poly aspartic acid. The content of amorphous iron oxide could be significantly increased by adding bothγ-poly-glutamic acid and poly aspartate acid in paddy soil derived from meadow soil, and the complexed iron oxide increased by 136.24% and 12.00% compared with that of control, respectively. The addition ofγ-poly-glutamic acid effectively increased the content of amorphous and complex iron oxide in paddy soil derived from littoral saline soil. In conclusion, no significant difference in the content of free iron oxide was observed in the three paddy soils with treatment ofγ-poly-glutamic acid addition. While the addition ofγ-poly-glutamic acid effectively increased the contents of amorphous and complex iron oxide, but decreased the crystallization rate of iron oxide, which is helpful to improve the content of available Fe. Furthermore, it also activated the iron oxide significantly and restrained the crystallization of iron oxide in three paddy soils. While the application of poly aspartic acid had no obvious excitation effect on complexed and amorphous iron oxide.