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将采自世界各地的未耕作、未施肥的120个表土样品(A_1层)分为石灰性土壤,轻度风化土壤(主要是软土),和高度风化土壤(主要是氧化土和老成土)。对不同风化程度的土壤,用Bray Ⅰ(NH_4F+HCl)、Mehlich Ⅰ(HCl+H_2SO_4)、Olsen(NaHCO_3)和Texas A和M(NH_4Ae+EDTA)等方法进行磷素肥力测定和磷素的连续分级(树脂-NaHCO_3-NaOH-HCl),以确定这些土壤磷素中树脂提取的活性磷与更稳定的无机和有机磷组分中测定值的相对贡献。以Bray Ⅰ、MehlichⅠ和Texas A和M法从石灰性土壤中提取出的磷,明显的高于高度风化土壤(5%水准),这是因为这些酸性提取剂溶解了石灰性土壤中的磷酸钙而引起的。随着土壤风化程度的增加,从磷酸钙向磷酸铝和磷酸铁的转化是明显的。在石灰性轻度风化和高度风化土壤中磷酸钙占全磷量的百分数分别为55%、17%和14%;而在这三组土壤中相应的Al-P和Fe-P的含量占全磷的百分数分别为4%、12%和20%。高度风化土壤中有机磷的含量(112mgkg~(-1),占全磷的26%)比石灰性土壤(36mgkg~(-1),占全磷的7%)明显较高(5%显著水准)。土壤磷的测试值与磷各组分间的相关性表明:对轻度风化土壤尽管所有方法的测试值与树脂磷是密切相关的,但对石灰性土壤只有Olsen法测试的磷与树脂密切相关(1%显著水准),而对高度风化土壤除Olsen法外,其它所有方法的测试值与树脂磷均高度相关。高度风化土、石灰性土壤、及轻度风化土壤中有机磷分别为平均17%、4%、1%,这就解释了BrayⅠ、Mehlich Ⅰ和Texas A和M法测得磷含量较高的原因。未耕作的高度风化土壤中,有机磷与土壤测试磷之间的关系是确定无疑的,在评价这些土壤的磷素肥力时对此必须慎重考虑。
120 topsoil samples (A_1) from un-cultivated and non-fertilized areas from all over the world were classified into calcareous soil, slightly weathered soil (mainly soft soil) and highly weathered soil (mainly oxidized soil and mature soil) . The effects of Bray Ⅰ (NH_4F + HCl), Mehlich Ⅰ (HCl + H_2SO_4), Olsen (NaHCO_3), Texas A and M (NH_4Ae + EDTA) on soil fertility and phosphorus The grade (resin -NaHCO 3-NaOH-HCl) was fractionated to determine the relative contribution of the resin-extracted reactive species in these soil phosphorus to the measured values in the more stable inorganic and organophosphorus fractions. Phosphorus extracted from calcareous soils by the Bray I, Mehlich I, and Texas A and M methods is significantly higher than highly weathered soils (5% level) because these acidic extractants dissolve calcium phosphates in calcareous soils Caused by. As the degree of soil weathering increases, the conversion from calcium phosphate to aluminum phosphate and iron phosphate is evident. Calcium phosphate accounted for 55%, 17% and 14% of the total phosphorus in the calcareous and highly weathered soils, respectively, while the contents of Al-P and Fe-P in these three soils were all The percentage of phosphorus was 4%, 12% and 20% respectively. The contents of organic phosphorus (112mgkg -1, accounting for 26% of total phosphorus) in highly weathered soils were significantly higher than those in calcareous soils (36mgkg -1, accounting for 7% of total phosphorus) (5% significant level ). The correlation between the measured values of soil phosphorus and the components of phosphorus shows that for mildly weathered soils, although the measured values of all the methods are closely related to the resin phosphorus, only phosphorus measured by the Olsen method for calcareous soils is closely related to the resin (1% significant), while for all highly weathering soils except for the Olsen method, all other test values are highly correlated with resin phosphorus. Organic phosphorus in highly weathered soils, calcareous soils, and lightly weathered soils averaged 17%, 4%, and 1%, respectively, which explains the reason for the higher phosphorus content measured by the Bray I, Mehlich I, and Texas A and M methods . Among uncultivated highly weathered soils, the relationship between organic phosphorus and soil-tested phosphorus is certain, and must be carefully considered when evaluating the phosphorus fertility of these soils.