添加氧化镁和铵明矾对菜田高磷土壤活性磷的影响

Effect of magnesium oxide and alum addition on soil labile phosphorus in a high P content vegetable field

为研究不同种类钝化剂对土壤磷素的固定效果,通过室内培养试验,向土壤中添加氧化镁、铵明矾及二者不同比例的混合物,研究其对土壤0.01 mol·L^(-1)CaCl_2浸提磷、0.5 mol·L^(-1)NaHCO_3浸提磷含量及磷素组分的影响。结果表明:与未钝化的对照处理相比,向土壤分别添加0.5%和2.0%(m/m)的氧化镁、铵明矾或其混合物培养45 d后,均显著降低了土壤CaCl_2浸提磷含量。添加氧化镁或铵明矾分别降低了87.8%(0.5%)、98.0%(2.0%)和44.4%(0.5%)、88.8%(2.0%)的CaCl_2浸提磷含量,而二者混合物的钝化效果明显弱于氧化镁。添加2.0%的氧化镁、铵明矾或其混合物对土壤NaHCO_3浸提磷含量降低明显,但氧化镁和铵明矾的混合物降低土壤NaHCO_3浸提磷的效果弱于铵明矾。对培养45 d后的土壤进行Hedley分组测定磷素组分发现,添加氧化镁或铵明矾显著降低了土壤H_2O浸提总磷和NaHCO_3浸提总磷含量,添加铵明矾显著增加了土壤中Na OH浸提总磷的含量。氧化镁、铵明矾和土壤活性磷不同的作用机理是导致氧化镁固定CaCl_2-P效果显著而铵明矾固定Olsen-P效果显著的主要原因。

In order to study the effect of different kinds of phosphorus（P）stabilization materials on the fixation of soil P, an incubation experiment was conducted to investigate the abilities of magnesium oxide（Mg O）, alum, and their mixtures at different ratios to reduce 0.01 mol·L^（-1） CaCl2 extracted P（CaCl2-P）, 0.5 mol·L^（-1） NaHCO3 extracted P（Olsen-P）, and the soil P fraction. The results indicated that the addition of Mg O and alum could significantly decrease the soil CaCl2-P level compared with the control treatment, and this occurred at both 0.5% and 2.0% soil dry weight. After 45 d incubation, Mg O decreased soil CaCl2-P by 87.8%（0.5%）and 98%（2.0%）, whereas alum addition reduced soil CaCl2-P by 44.4%（0.5%）and 88.8%（2.0%）. The Mg O, alum, or a mixture addition at 2.0% soil dry weight significantly decreased soil Olsen-P level. The decline of soil CaCl2-P and Olsen-P influenced by the mixture of Mg O and alum was less effective than that of Mg O and alum, respectively. The results after measuring the soil P fraction by Hedley fractionation indicated that Mg O or alum addition significantly decreased the soil labile P level, and alum significantly increased the Na OH extracted P content compared to the control treatment. In general, Mg O significantly decreased the CaCl2-P levels, but alum also significantly decreased the Olsen-P due to the different P fixation mechanism.