土壤腐殖物质组分结合态磷素有效性的研究

以棕色针叶林土、暗棕壤和黄棕壤为供试土壤，采用常规的碱（0.1 mol L?1 NaOH + 0.1 mol L?1 Na₄P₂O₇）提取液酸化法分离出胡敏酸（HA），碱不溶性的粗胡敏素（CHU）再经10%HF-HCl处理得到去除矿质灰分后纯化的胡敏素（PHU）；利用酶水解和紫外照射方法，分析了上述各腐殖物质组分结合态磷素的有效性。结果表明:供试腐殖物质组分中磷含量以HA最高，其次为PHU，而CHU最低；HA、CHU和PHU中分别有32.1% ~ 51.7%、17.2% ~ 28.5%和22.3% ~ 35.7%的磷是以活性无机磷的形式存在，而29.5% ~ 37.6%、20.6% ~ 31.1%和26.2% ~ 41.5%的磷是以活性有机磷的形式存在；活性有机磷中，类植酸态磷的比例（9.51% ~ 27.6%）最高，其次为简单单酯磷（5.89% ~ 13.7%），而多核苷酸磷的比例（1.03% ~ 9.28%）最低；与未经紫外照射的样品相比，紫外照射合并酶水解使HA、CHU和PHU中活性磷的比例分别增加了0.90% ~ 3.77%、0.73% ~ 7.57%和0.69% ~ 3.91%；几种腐殖物质组分中，总活性磷的顺序为HA > PHU > CHU，而惰性磷的顺序则与之相反；总活性磷与Al含量呈显著负相关，而惰性磷则与Al含量呈显著正相关。上述结果说明，不同腐殖物质组分结合态磷素的有效性不同，其中HA结合态磷素的有效性最高，其次为PHU，而CHU结合态磷素的有效性最低，Al的存在能够抑制腐殖物质组分结合态磷素的有效性。

Availability of Phosphorus Associated with Soil Humic Substance

In this study, humic substance fractions were extracted from Brown coniferous forest soil, Dark Brown soil, and Yellow Brown soil. Humic acid (HA) was separated by acidification using a conventional method of alkali (0.1 mol L?1 NaOH + 0.1 mol L?1 Na₄P₂O₇) extraction procedure. Alkali-insoluble crude humin (CHU) was treated with 10% HF-HCl to obtain pure humin (PHU) through removal of mineral ash. The availability of humic substance fractions-bound phosphorus (P) was analyzed using the methods of enzymatic hydrolysis and ultraviolet irradiation. The results showed that the content of P in the tested humic substance components was the highest in HA, followed by PHU, and the lowest in CHU. About 32.1%-51.7%, 17.2%-28.5% and 22.3%-35.7% of HA, CHU and PHU -bound P were in the form of labile inorganic P, while 29.5%-37.6%, 20.6%-31.1% and 26.2 %-41.5% of them was in the form of labile organic P. In the labile organic P, phytate-like P displayed the highest proportion (9.51%-27.6%), followed by simple monoester P (5.89%-13.7%), and the proportion of polynucleotide P (1.03%-9.28%) was the lowest. Compared with samples without UV irradiation, UV irradiation combined with enzymatic hydrolysis increased the proportion of labile P in the HA, CHU, and PHU fractions by 0.90%-3.77%, 0.73%-7.57%, and 0.69%-3.91%, respectively. The content of total labile P in the humic substance components decreased in the order of HA > PHU > CHU, while the opposite order was found in the content of recalcitrant P. Total labile P was significantly negatively correlated with Al content, while recalcitrant P was significantly positively correlated with Al content. The availability of HA-bound P was the highest, followed by that of PHU-bound P, and that of CHU-bound P was the lowest. The existence of Al can inhibit the availability of humic substance -bound P.