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土壤中磷酸固定作用每受外界环境之影响而有很大差异,如粘土矿物的种类,土壤反应,代换性盐基等,黏土矿物与土壤反应对于磷酸固定前,人已有较详细之报告,本文特重视代换性盐基之种类对于磷酸固定之关系。本试验以紫色土与黄壤为代表,均取于北碚。紫色土系发育于白垩纪自流井层紫色页岩,属中性而无石灰性反应,pH=7.0,黄壤系自侏罗纪灰色砂岩风化者,心土微红,pH=4.5—5.0,为避免过高之有机质,均采取心土,按照 Stoke 氏定律提取5微米(micron)直径之黏土粒,晒干后,分别以 N NaCl,N KGl,N NH_4Cl,N MgCl_2,N BaCl_2及 pH=3 HCl 处理,然后再以90%酒精洗涤至无氯为止,总之以不变更胶体之构造为原则,经处理之黏土,先分析其中之代换性盐基以及盐基代换总量,然后再测定其磷酸固定量,在酸性反应如 H~-黏土,其磷酸固定之主要因子为水化铁及水化铝,故再以 pH=2之盐酸淋洗,除去其中游离铁铝,再测定其磷酸固定量以资比较。按分析结果,黄壤胶体(<2 micron)中之(SiO_2)/(R_2O_3)为2.19,紫色土为2.56,前者盐基代换总量每百克黏土粒(<5 micron)为18m.e.后背为30m.e.,兹将试验所得结果归纳如次: 1.磷酸固定量每因土壤胶体之不同而有差异,由黄壤所提取之黏土其磷酸固定量亦较紫色土为高。 2.土壤之磷酸固定量,非特因土壤胶体之不同而有差异,即或同一黏土,其磷酸固定量亦因其代换性盐基之不同而有差异,概言之,钠黏土之磷酸固定量为最小,钾黏土次之钡、铵黏土又次之,而以钙黏土为最大,其磷酸固定次序为: Ca-黏土>Mg-黏土>H-黏土>B(?)-黏土>NH_4-黏土>K-黏土>Na 黏土 3.各种不同代换性盐基的粘土,加磷酸溶液后,其反应亦各不相同,H~-黏土之 pH 值为3.2—4.5,因其酸度较高,溶液中之游离铁与游离铝含量较多,是故磷酸固定量亦较高,如以淡盐酸(pH=2)洗涤,除去其中游离铁铝后,其磷酸固定量则大为减少,Na~-黏土与 K~-粘土之溶液中,因 OH 离子较多(pH=8.0—8.6),而磷酸钠与磷酸钾又为水溶性,故磷酸固定量为最少。Ca~-粘土与 Mg-粘土其反应属中性至微碱性,pH=7.5—8.0,因溶液中 Ca,Mg 离子浓度较高,磷酸则为此 Ca,Mg离子所固定,故在中性土壤中,磷酸固定以 Ca 为其主要在子,酸性土壤则以水化铁为其主要因子。 4.钙粘土所固定之磷酸,如以0.002 N H_2SO_4提取,其所固定之磷酸复可溶解,是项固定之磷酸与 Heck 所称「暂时固定磷酸」颇为相似。
Phosphoric acid fixation in soil varies greatly depending on the external environment. For example, the type of clay minerals, soil reaction, substitutional salt base, etc., clay minerals and soil reactions have been reported in more detail before phosphoric acid fixation , This article special emphasis on the type of substitutional base for phosphate fixation. The purple purple soil and yellow soil as the representative, are taken Beibei. Purple soil system developed in the Cretaceous artesian well purple shale, is neutral without any calcareous reaction, pH = 7.0, the yellow soil from the Jurassic gray sandstone weathering, soil reddish, pH = 4.5-5.0, to avoid Excessive organic matter is taken from the heart and soil, according to the Stoke’s law to extract 5 micron diameter clay particles, after drying, respectively, N NaCl, N KGl, N NH 4 Cl, N MgCl 2, N BaCl 2 and pH = 3 HCl Treatment, and then to 90% alcohol to chlorine-free so far, in short, without changing the principle of colloidal structure, treated clay, first analysis of the substitutional base and the total amount of base substitution, and then measured The amount of phosphoric acid fixed, in the acidic reaction such as H ~ - clay, the main factor of its phosphoric acid fixation of hydrated iron and aluminum hydride, and then pH = 2 hydrochloric acid leaching, to remove the free iron and aluminum, and then determine the phosphate immobilization To compare the amount of money. According to the analysis results, the (SiO 2) / (R 2 O 3) of the yellow colloids (<2 micron) was 2.19 and that of the purple soil was 2.56. The former was 18 m.e. per 100 g of clay particles (<5 micron). The back is 30m.e., we will summarize the test results are as follows: 1. Phosphate fixed amount due to different soil colloids are different from the yellow soil extracted clay phosphate fixation is also higher than purple soil. 2. Phosphate fixed amount of soil, non-special because of different soil colloids are different, that is, or the same clay, the fixed amount of phosphoric acid because of its substitutional base vary, in general, the sodium phosphate fixed phosphate The amount of potassium clay is the second, followed by clay and barium, while clay is the largest. The order of phosphate fixation is Ca-clay> Mg-clay> H-clay> B (?) - clay> NH_4- Clay> K-Clay> Na Clay 3. The various alternative base salts of the clay, the addition of phosphoric acid solution, the reaction is also different, H ~ - clay pH value of 3.2-4.5, because of its high acidity , The solution of free iron and free aluminum content is more, so the fixed amount of phosphoric acid is also higher, such as with light hydrochloric acid (pH = 2) to wash, remove the free iron and aluminum, the phosphate fixed amount is greatly reduced, Na ~ - clay and K ~ - clay solution, due to more OH ions (pH = 8.0-8.6), and sodium phosphate and potassium phosphate is water-soluble, so the fixed amount of phosphoric acid is the least. Ca ~ - clay and Mg - clay reaction is neutral to slightly alkaline, pH = 7.5-8.0, due to the high concentration of Ca, Mg ions in the solution, while the phosphate is Ca, Mg ions fixed, it is neutral In the soil, the fixation of phosphoric acid to Ca is mainly in the son, while the acid soil is the main factor in the hydrous iron. 4. The calcium phosphate immobilized phosphoric acid, such as 0.002 N H 2 SO 4 extraction, the immobilization of phosphoric acid can be dissolved, the fixed phosphoric acid and Heck called “temporary fixed phosphoric acid” is quite similar.