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CHANGES IN SOIL ORGANIC MATTER AND PHOSPHORUS DURING CULTIVATION OF GRASSLAND SOILS.

机译：草地土壤耕作过程中土壤有机质和磷素的变化。

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摘要

This study attempts to quantify the losses of C, N, and P from three prairie soils of different textures during cultivation. For this purpose cultivated and adjacent uncultivated soils were sampled and their C, N, and P contents as well as their bulk densities and horizon depths were compared.;Losses of C, N, and P from soil particle-size fractions during cultivation were examined. Four years of cultivation of a silt loam resulted in an extensive depletion of organic matter associated with particles > 50 (mu)m (43% of the initial C lost). With continued cultivation this accumulated material was slowly transformed within the system, accompanied by net losses of 34% C and 29% N from the total soil over 60 years. Fine clay (> 0.2 (mu)m) associated organic matter was rapidly depleted during the first 60 years but showed little change thereafter. Losses of fine silt (5 to 2 (mu)m) and coarse clay (2 to 0.2 (mu)m) associated organic materials were substantially less, and the proportion of total soil organic matter in these forms increased with time of cultivation.;A sequential chemical extraction was used to remove several forms of inorganic phosphorus (Pi) and organic phosphorus (Po). In the uncultivated coarse-textured soil significant amounts (7%) of secondary (NaOH extractable) Pi forms were associated with high levels of labile (bicarbonate and resin extractable) Pi. These secondary Pi forms, which were concentrated in the finer particle size fractions ( > 2 (mu)m), contributed to the P loss during cultivation, whereas all P loss in the silt-loam soils was due to Po losses alone. Labile P fractions were greatly reduced during cultivation, indicating a significant reduction in available P and P fertility of cultivated soils which was closely tied to soil organic matter losses.;Reductions of about 35% in the C concentration were observed in clay and silt loam soils after 60 to 70 years of cultivation. At the same time reductions in N concentrations were greatly influenced by the presence or absence of legume crops grown in the fields and losses varied between 18 and 34%. Phosphorus concentrations were reduced by 12% and all P losses were accounted for by the organic fraction. During a similar period of cultivation a lighter textured sandy loam had experienced greater reductions in C, N, and P concentrations of 46, 46, and 29%, respectively. Prolonged cultivation of 90 years did not result in a decrease in the rates of losses of C, N, and P on the silt loam soil. Conversion of concentration data to area based total C, N, and P budgets resulted in a decrease in the differences seen between cultivated and uncultivated soils.
机译：这项研究试图量化耕作过程中三种质地不同的草原土壤中C，N和P的损失。为此，对耕种和邻近的未耕种土壤进行采样，并比较它们的C，N和P含量，以及其容重和水平深度。;检查了耕作过程中土壤粒度级分中C，N和P的损失。淤泥质壤土的耕种四年导致大量有机物的消耗与大于50μm的颗粒（初始C损失的43％）有关。随着持续耕种，这种积累的物质在系统内缓慢转化，伴随着60年间土壤中的净损失34％的C和29％的N。在最初的60年中，细粘土（> 0.2μm）相关的有机物质迅速枯竭，但此后几乎没有变化。细粉土（5至2μm）和粗粘土（2至0.2μm）相关的有机物质的损失显着减少，并且这些形式的总土壤有机质的比例随耕种时间的增加而增加。使用顺序化学萃取来去除几种形式的无机磷（Pi）和有机磷（Po）。在未经耕种的粗纹理土壤中，大量（7％）可再生（可提取的NaOH）的Pi形式与不稳定（碳酸氢盐和可提取树脂的）Pi的含量较高相关。这些次要的Pi形式集中在较细的颗粒级分（> 2μm）中，这在耕作过程中造成了P的损失，而粉壤土中的所有P损失都是由于Po的损失。耕作过程中不稳定的磷含量大大降低，这表明耕作土壤的有效磷和磷肥力显着降低，这与土壤有机质流失密切相关；在黏土和粉壤壤土中观察到碳浓度降低了约35％经过60到70年的种植。同时，田间生长的豆类作物的存在与否极大地影响了氮含量的降低，损失在18％至34％之间。磷浓度降低了12％，所有P的损失均由有机部分引起。在相似的耕种期间，质地较轻的砂质壤土的C，N和P浓度分别降低了46％，46％和29％。 90年的长期耕作不会导致粉壤土土壤上C，N和P的流失速率降低。将浓度数据转换为基于面积的总C，N和P预算后，耕种和未耕种土壤之间的差异减小了。

著录项

  • 作者

    TIESSEN, HOLM.;

  • 作者单位

    The University of Saskatchewan (Canada).;

  • 授予单位 The University of Saskatchewan (Canada).;
  • 学科 Agriculture Agronomy.
  • 学位 Ph.D.
  • 年度 1982
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  • 原文格式 PDF
  • 正文语种 eng
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