铁氧化物影响土壤硝化作用动力学的作用机制

为探究铁氧化物对土壤硝化动力学的影响,以全铁含量低的酸性潮土(pH4.9)和中性潮土(pH7.2)为研究对象,通过7d的室内恒温(28℃)培养,研究了不同pH土壤在添加0(对照),0.5%,1%,3%,5%,10%(重量比)铁氧化物后的硝化动力学过程。结果表明:铁氧化物加入量超过3%,则改变中性潮土的硝化动力学过程由一级变为零级模型。不同含量铁氧化物加入后,酸性潮土的硝化过程均符合一级动力学模型。加铁处理的酸性潮土,其净矿化速率均显著高于不加铁处理。加铁量为10%处理的净矿化速率为4.12mg/(kg·d),是不加铁处理的7.82倍。随着铁氧化物加入量的增加,酸性潮土净硝化速率显著升高而中性潮土净硝化速率却显著下降。酸性潮土中铁氧化物加入量超过3%的处理,其净硝化速率极显著高于加铁量小于3%的处理。总之,铁氧化物的加入显著促进酸性潮土的净硝化速率,对中性潮土的净硝化速率却有显著抑制作用,并且加入量越大对2种土壤的作用效果越显著。3%的铁氧化物加入量是显著影响酸性潮土和中性潮土硝化作用的临界值。

Mechanisms of Fe Oxide's Effects on Nitrification Kinetics in Soils

In order to quest the effects of Fe oxide on nitrification in soils, a acidic fluvo-aquic soil (pH 4.9) and neutral fluvo-aquic soil (pH 7.2) with low total iron were selected as materials. Indoor incubation method?was used to investigate the time-dependent kinetic of net nitrification after the two soils were amended with 0% (control), 0.5%, 1%, 3%, 5%, 10% Fe oxide by weight. The results showed that, nitrification was best fitted by a first-order kinetic model for neutral soil with less than 3% Fe oxide amendment. However, it was best fitted by a zero-order kinetic model when more than 3% Fe oxide were added. For acid soil, nitrification was best fitted by a first-order kinetic model regardless of the addition amount of Fe oxide. Net mineralization rate of the acid soil increased significantly after the addition of different amount Fe oxide, and the highest mineralization rate was found for 10% Fe oxide amendment (4.12 mg/(kg·d)), which was 7.82 times higher than unamended soil. With the increase of iron oxide addition amount, the net nitrification rate of acid soil significantly increased while the net nitrification rate of neutral soil decreased significantly. The net nitrification rates of acid soil with 3% and more Fe oxide amendment were extremely significantly higher than that of soils with less amendment. Overall, Fe oxide addition stimulated net nitrification rates in the low pH soil (pH 4.9), while the opposite occurred in the high pH soil (pH 7.2), and the greater amount wereadded, the more significant effects were observed. 3% Fe oxide amendment was the critical value that significantly influence nitrification of the acid fluvo-aquic soil and neutral fluvo-aquic soil.