磷矿粉在酸性土壤中的施用: 比较磷酸盐提取方法测定磷矿粉溶解程度

Three phosphate extraction methods were used to investigate the dissolution,availability and transfo-mation of Kunyang phosphate rock(KPR) in two surface acid soils.Dissolution was determined by measuring the increase in the amounts of soluble and adsorbed inorganic phosphate fractions,and did not differ signifi-cantly among the three methods.Significant correlations were obtained among P fractions got by the three extraction methods.Dissolution continued until the end of the 90-day incubation period.At the end of the period,much of the applied phosphate recovered in both soils were in the Al- and Fe-P or in the hydroxide-and bicarbonate-extractable inorganic P fractions.The dissolution of KPR in the two soils was also similar: increased addition of phosphate rock resulted in decreased dissolution.The similarity in the order and extent of dissolution in the two soils was probably due to the similarity in each soil of several factors that are known to influence phosphate rock dissolution,namely low CEC,pH,P level,and base status;and high clay and free iron and aluminum oxide contents.The results suggested that KPR could be an aternative P source in the soils are not limiting.     

Mobilization and immobilization of dissolved organic matter in forest soils

Field and laboratory studies combined with destructive and nondestructive analytical methods were used to characterize dissolved organic matter (DOM) in acid forest soils. DOM is produced in significant amounts in the forest canopy and in the forest floor. A major part of the organic solutes are lignocellulose-degradation products being strongly microbially altered in the course of ligninolysis. The release of lignin-derived moieties into the soil solution is controlled by their degree of biooxidation. Microorganisms contribute also directly to the organic solutes through the release of microbial metabolites. DOM released from the forest floor passes the upper mineral soil almost conservatively, whereas in the subsoil most DOM is removed from solution. Immobilization of DOM is mainly due to sorption on Fe and Al oxides. The highly oxidized lignin-derived moieties are preferentially removed from the soil solution whereas the saccharides are relatively enriched. We conclude that DOM in the forest soil output to the hydrosphere is a result of (1) the release of microbially degraded lignocellulose compounds and of microbial metabolites into the forest floor solution and (2) selective sorptive removal of the lignin-derived constituents in the subsoil.     

Soil phosphorus mobilization in different taxonomic orders

Changes in P fractions using Hedley's sequential fractionation of organic and inorganic soil P, were studied in soils covering a wide range of developmental stages and original materials. A greenhouse experiment was performed in order to make an exhaustive P uptake by Lolium perenne and to study soil phosphorus mobilization from different fractions. Samples were obtained at 30, 60 and 90 days from sowing, with two fertilization rates added as KH₂PO₄. The exhaustion produced by plants resulted in different patterns of mobilization according to soil characteristics. For control soils the contents of inorganic labile fraction (LIP) decreased at the end of the experience in Mollisol (31%), Vertisol (24%) and Andisol (17%). The mobilization of organic P was greater for Ultisol and Andisol (77 and 75% respectively) than for the other soils. Fertilization affected mainly inorganic P, with a significant increase in contents of LIP in Entisol (46%) and moderately resistant inorganic P (MRIP) in Andisol (15%). Inorganic P/organic P relationship tended to increase during the experiment, while labile P/moderately resistant P increased in Entisol and Mollisol.     

Phosphorus forms as affected by abandoned anthills (Formica polyctena Förster) in forest soils: sequential extraction and liquid-state 31P-NMR spectroscopy

Ants are known to concentrate phosphorus (P) inside their nests via collection of food and litter. To elucidate the possible effects on long-term availability of soil P, five anthills abandoned by Red wood ant (Formica polyctena Förster) > 5—20 years ago were characterized for soil P forms in a temperate Danish deciduous forest. Sequentially extracted P fractions and liquid-state ³¹P nuclear magnetic resonance (NMR) spectra were obtained on surface samples (0—10 cm) from abandoned anthills and adjacent topsoil; in addition one representative soil profile in an abandoned anthill was investigated. The results show that different inorganic and all organic P fractions were enriched by a factor of 2.0—3.3 inside anthills relative to the surrounding soil. The soil underneath the abandoned anthill had higher P contents until 50-cm depth. Phosphorus composition was less affected by former anthill construction. Only the younger anthills revealed a preferential accumulation of labile organic P forms such as Na-HCO₃ extractable P or diester P. The accumulation of the stable and moderate labile P forms, however, persisted for ≥ 20 years after abandonment. We concluded that former ant activity enhanced long-term P availability of soil due to high local P inputs, whereas changes of the P form distribution lasted 5—10 years after nest abandonment.     

Carbon storage in loess derived surface soils from Central Germany: Influence of mineral phase variables

The influence of the soil mineral phase on organic matter storage was studied in loess derived surface soils of Central Germany. The seven soils were developed to different genetic stages. The carbon content of the bulk soils ranged from 8.7 to 19.7 g kg^—1. Clay mineralogy was confirmed to be constant, with illite contents > 80 %. Both, specific surface area (SSA, BET‐N₂‐method) and cation exchange capacity (CEC) of bulk soils after carbon removal were better predictors of carbon content than clay content or dithionite‐extractable iron. SSA explained 55 % and CEC 54 % of the variation in carbon content. The carbon loadings of the soils were between 0.57 and 1.06 mg C m^—2, and therefore in the ”︁monolayer equivalent” (ME) level. The increase in SSA after carbon removal (ΔSSA) was significantly and positively related to carbon content (r² = 0.77). Together with CEC of carbon‐free samples, ΔSSA explained 90 % of the variation in carbon content. Clay (< 2 μm) and fine silt fractions (2—6.3 μm) contained 68—82 % of the bulk soil organic carbon. A significantly positive relationship between carbon content in the clay fraction and in the bulk soil was observed (r² = 0.95). The carbon pools of the clay and fine silt fractions were characterized by differences in C/N ratio, δ¹³C ratio, and enrichment factors for carbon and nitrogen. Organic matter in clay fractions seems to be more altered by microbes than organic matter in fine silt fractions. The results imply that organic matter accumulates in the fractions of smallest size and highest surface area, apparently intimately associated with the mineral phase. The amount of cations adhering to the mineral surface and the size of a certain and specific part of the surface area (ΔSSA) are the mineral phase properties which affect the content of the organic carbon in loess derived arable surface soils in Central Germany most. There is no monolayer of organic matter on the soil surfaces even if carbon loadings are in the ME level.     

Sequentially extracted phosphorus fractions in peat‐derived soils

Phosphorus (P) forms were sequentially extracted from peat derived soils (Eutric Histosols and Gleysols) at eight sites in Saxony‐Anhalt (Germany) to disclose general differences in P pools between mineral and organic soils and to investigate effects of peat humification and oxidation in conjunction with land use and soil management on the P status of soils. Overall 29 samples providing a wide variety of basic chemical properties were subjected to the Hedley fractionation. The Histosol topsoils contained more total P (P_t) (1345 ± 666 mg kg^—1) than the Gleysol topsoils (648 ± 237 mg kg^—1). The predominant extractable fractions were H₂SO₄‐P (36—63 % of P_t) in calcareous and NaOH‐P_o (0—46 % of P_t) in non‐calcareous Histosols. These soils had large pools of residual P (13—93 % of P_t). Larger contents and proportions of P_o and of labile P fractions generally distinguished organic from mineral soils. Regression analyses indicated that poorly crystalline pedogenic oxides and organic matter were binding partners for extractable and non‐extractable P. Intensive management that promotes peat humification and oxidation results in disproportional enrichments of labile P fractions (resin‐P, NaHCO₃‐P_i, and NaHCO₃‐P_o). These changes in P chemistry must be considered for a sustainable management of landscapes with Histosols and associated peat derived soils.     

外源秸秆对污染土壤氧化还原过程水分散性胶体态重金属的影响

土壤胶体尤其是水分散性胶体，作为一种重要的污染物载体，在重金属吸附、迁移以及生物吸收过程起着重要作用。通过土壤培养试验探讨了外源添加水稻秸秆在氧化还原波动条件下如何影响土壤液相中及水分散性胶体中重金属的分布。结果表明，外源秸秆增加厌氧过程液相中溶解性有机碳(DOC)、砷(As)、铁(Fe)、锰(Mn)、钙(Ca)、钾(K)、硅(Si)、铝(Al)、镁(Mg)等浓度，降低了厌氧过程氧化还原电位(Eh)及铜(Cu)、铅(Pb)等浓度，提高了好氧过程Pb浓度。利用非对称流场流分馏-紫外可见-电感耦合等离子体-质谱联用技术(AF4-UV-ICP-MS)，测得水分散性胶体颗粒主要分布在0.3~3 kDa、3~40 kDa和130 kDa~450 nm三个粒径范围，各粒径颗粒的组成有所差异，主要含有机质、无机黏土矿物和铁矿物等。外源秸秆促进液相中Fe和As由胶体态向溶解态转化，促进镉(Cd)和Cu由溶解态向胶体态转化。本研究有助于揭示农业活动影响重金属迁移转化及有效性的界面机制。     

灌丛化对高寒草地土壤有机碳组分的分异研究

草地灌丛化过程中植被优势群落类型的转变会通过凋落物及根系分泌物的数量和性质差异影响土壤有机碳（SOC）组分。为探索高寒草地土壤不同活性有机碳组分对灌木侵入的响应，本研究采用Stewart物理-化学联合分组方法，将青藏高原东缘四种典型灌丛化草地以及未灌丛化草地土壤有机碳分为游离态活性有机碳（nonprotected organic carbon，Non-C）、物理保护态有机碳（physically-protected organic carbon，Phy-C）、化学保护态有机碳（chemically-protected organic carbon，Che-C）和生物化学保护态有机碳（biochemically-protected organic carbon，Bio-C），分析不同活性有机碳组分含量变化及其影响因素。结果表明：（1）灌木侵入对高寒草地表层土壤（0~10 cm）SOC含量影响不显著（P>0.05），但不同活性有机碳组分含量有所分异。高山绣线菊（Spiraea alpina）和窄叶鲜卑花（Sibiraea angustata）灌木侵入降低了土壤Non-C和Bio-C组分（P<0.05）；金露梅（Potentilla fruticosa）灌木侵入降低了土壤Non-C组分（P<0.05）；小叶锦鸡儿（Caragana microphylla）灌木侵入降低了土壤Phy-C和Che-C组分（P<0.05），而提高了土壤Bio-C组分含量（P<0.05）。（2）未灌丛化草地和灌丛化样地土壤均以Non-C组分为主，其次是稳定态有机碳库（Che-C和Bio-C），而Phy-C占比最少。（3）土壤黏粒和全氮是影响高寒灌丛化草地土壤不同活性有机碳组分的主要因素，解释度共达51.2%。高寒草地灌木侵入过程中，灌木种类对不同活性土壤有机碳组分含量影响不一致，灌丛化草地和未灌丛化草地土壤表层均以Non-C为主，因此在外界扰动的情况下，该地区的有机碳库可能成为碳源。     

长期施肥下旱地红壤不同保护态有机碳库变化特征

为研究长期施肥对旱地红壤不同保护态有机碳组分（库）的影响，在不施肥（CK）、单施氮肥（N）、施常量氮磷钾肥（NPK）、施2倍量氮磷钾肥（HNPK）、氮磷钾肥配施有机肥（NPKM）、单施有机肥（M）6个处理下，分析物理-化学联合分组方法分离的土壤未保护、物理保护、物理-化学保护、物理-生物化学保护、化学保护、生物化学保护的有机碳组分的含量特征及其与总有机碳含量的关系，并探究土壤各保护态有机碳库储量与累积碳投入量间的关系。结果表明，CK与N处理间的土壤各保护态有机碳组分的含量均无显著差异（P>0.05）。与CK相比，施氮磷钾肥（NPK、HNPK）与有机肥（M、NPKM）处理的土壤总有机碳含量、未保护有机碳组分含量、物理保护有机碳组分含量分别提高13.3%~48.0%、39.2%~221.5%、41.9%~132.3%，土壤未保护有机碳、物理保护有机碳占土壤总有机碳的比例提高1.9~10.0、2.5~5.5个百分点，增幅均达显著水平（P<0.05），该效应在施有机肥条件下表现更为明显。土壤各保护态有机碳组分含量与总有机碳含量均呈正相关关系，线性回归方程拟合结果显示，单位总有机碳含量增加引起的未保护游离粗颗粒有机碳和物理保护有机碳含量的变化值分别达44.3%和28.0%（P<0.001）。除土壤生物化学保护有机碳外，其他保护态有机碳库的储量均与累积碳投入量呈极显著线性正相关（P<0.01）。研究表明，施肥后土壤增加的有机碳优先固存于未保护游离粗颗粒有机碳和物理保护有机碳组分中。与施化肥相比，有机培肥可更好地促进旱地红壤总有机碳的固存、提升有机碳的活性及增强有机碳的物理保护作用。在当前碳投入水平下，旱地红壤的生物化学保护有机碳可能已接近平衡状态。     

水稻吸收转运铁的生物地球化学机制研究进展

铁的生物吸收转移是环境中铁生物地球化学循环的重要过程之一，不仅控制着铁在稻米的累积，且影响水稻累积锌等养分元素及镉等重金属。阐明土壤-水稻体系中铁的吸收转移机制对深入理解稻田铁的环境行为与归趋具有重要的科学意义。主要介绍了水稻中铁吸收转运的功能基因、土壤-水稻系统铁同位素分馏及水稻植株中铁分布的光谱分析方法与手段，重点总结铁在水稻根部吸收及植物体内的转运过程，探讨铁对水稻根部锌和镉吸收的影响机制，可为提高水稻产量及改善稻米品质提供科学依据。