Assessment of bioavailable organic phosphorus in tropical forest soils by organic acid extraction and phosphatase hydrolysis.
Assessment of bioavailable organic phosphorus in tropical forest soils by organic acid extraction and phosphatase hydrolysis.
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DOI：
10.1016/j.geoderma.2016.08.018
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发表时间：
2016-12-15
期刊：
影响因子：
6.1
通讯作者：
Turner BL
中科院分区：
文献类型：
--
作者：
Darch T;Blackwell MS;Chadwick D;Haygarth PM;Hawkins JM;Turner BL
土壤有机磷有助于热带树木的营养，但在标准土壤磷测试中没有考虑到。植物和微生物可以释放有机阴离子来溶解土壤表面的有机磷，并合成磷酸酶从被溶解的化合物中释放无机磷酸盐。我们通过模拟有机酸和磷酸酶的分泌过程，开发了一种估算热带森林土壤生物可利用有机磷的方法。采用2 mM柠檬酸（即10 μmol g−1，近似根际浓度）与土壤pH比调整为4:1，提取5种不同性质（pH 4.4-6.1，总磷86-429 mg P kg−1）的低地热带森林土壤，提取时间为1 h。然后在土壤提取物中加入3种磷酸酶，以测定水解有机磷的形式。该方法提取的总磷在3.22至8.06 mg P kg - 1之间（平均为5.55±0.42 mg P kg - 1），其中平均四分之三为非活性磷（即有机磷加无机多磷酸盐）。在酶解的非活性磷中，28%是由牛肠粘膜磷酸单酯酶水解的简单磷酸二酯，18%是由柠檬酸青霉核酸酶和磷酸单酯酶联合水解的磷酸二酯，其余51%是由小麦中的广谱植酸酶水解的。结果表明，有机酸与磷酸酶的结合可使热带低地森林土壤有机磷被溶解和水解，这一途径可能对热带森林生物磷的获取有重要贡献。此外，我们还开发了一种可用于评估土壤有机磷生物有效性的方法。有机磷是热带森林生物群重要的磷源，其提取条件与土壤环境最接近
Soil organic phosphorus contributes to the nutrition of tropical trees, but is not accounted for in standard soil phosphorus tests. Plants and microbes can release organic anions to solubilize organic phosphorus from soil surfaces, and synthesize phosphatases to release inorganic phosphate from the solubilized compounds. We developed a procedure to estimate bioavailable organic phosphorus in tropical forest soils by simulating the secretion processes of organic acids and phosphatases. Five lowland tropical forest soils with contrasting properties (pH 4.4–6.1, total P 86–429 mg P kg− 1) were extracted with 2 mM citric acid (i.e., 10 μmol g− 1, approximating rhizosphere concentrations) adjusted to soil pH in a 4:1 solution to soil ratio for 1 h. Three phosphatase enzymes were then added to the soil extract to determine the forms of hydrolysable organic phosphorus. Total phosphorus extracted by the procedure ranged between 3.22 and 8.06 mg P kg− 1 (mean 5.55 ± 0.42 mg P kg− 1), of which on average three quarters was unreactive phosphorus (i.e., organic phosphorus plus inorganic polyphosphate). Of the enzyme-hydrolysable unreactive phosphorus, 28% was simple phosphomonoesters hydrolyzed by phosphomonoesterase from bovine intestinal mucosa, a further 18% was phosphodiesters hydrolyzed by a combination of nuclease from Penicillium citrinum and phosphomonoesterase, and the remaining 51% was hydrolyzed by a broad-spectrum phytase from wheat. We conclude that soil organic phosphorus can be solubilized and hydrolyzed by a combination of organic acids and phosphatase enzymes in lowland tropical forest soils, indicating that this pathway could make a significant contribution to biological phosphorus acquisition in tropical forests. Furthermore, we have developed a method that can be used to assess the bioavailability of this soil organic phosphorus. Development of a method to quantify biologically-available soil organic phosphorus Extraction conditions standardised to those which best approximate soil environment Organic phosphorus is an important phosphorus source for tropical forest biota
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影响因子：
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