不同Zn浓度对黑麦草根分泌物、根际Zn形态及植物Zn蓄集的影响

A glasshouse experiment was conducted using a root-bag technique to study the root exudates, rhizosphere Zn fractions, and Zn concentrations and accumulations of two ryegrass cultivars (Lolium perenne L. cvs. Airs and Tede) at different soil Zn levels (0, 2, 4, 8, and 16 mmol kg-1 soil). Results indicated that plant growth of the two cultivars was not adversely affected at soil Zn level≤8 mmol kg-1. Plants accumulated more Zn as soil Zn levels increased, and Zn concentrations of shoots were about 540 /μg g-1 in Aris and 583.9μg g-1 in Tede in response to 16 mmol Zn kg-1 soil. Zn ratios of shoots to roots across the soil Zn levels were higher in Tede than in Airs, corresponding with higher rhizosphere available Zn fractions (exchangeable, bound to manganese oxides, and bound to organic matter) in Airs than in Tede. Low-molecular-weight (LMW) organic acids (oxalic, tartaric, malic, and succinic acids) and amino acids (proline, threonine, glutamic acid, and aspartic acid, etc.) were detected in root exudates, and the concentrations of LMW organic acids and amino acids increased with addition of 4 mmol Zn kg-1 soil compared with zero Zn addition. Higher rhizosphere concentrations of oxalic acid, glutamic acid, alanine, phenylalanine, leucine, and proline in Tede than in Airs likely resulted in increased Zn uptake from the soil by Tede than by Airs. The results suggested that genotypic differences in Zn accumulations were mainly because of different root exudates and rhizosphere Zn fractions.     

镉污染土壤根际环境的调节与植物修复研究进展

简要回顾了近年来土壤镉污染现状,介绍了根际环境的调节作用、镉污染土壤的植物修复技术的类型、特点及植物修复情况,并对今后植物修复发展前景作了进一步展望,为实现对镉污染土壤进行有效的生态整治与安全高效益的利用提供了新的技术途径。     

Bioavailability of zinc and lead from a contaminated soil amended with pine bark-goat manure compost

The distribution in soil and plant uptake of zinc (Zn) and lead (Pb) as influenced by pine bark-goat manure (PBG) compost additions were investigated from the soils artificially contaminated with Zn or Pb ions using maize (Zea mays L.) as a test crop. Soils were amended with four rates of pine bark-goat manure compost (0, 50, 100, and 200 tons ha^?1) and four rates (0, 300, 600 and 1200 mg kg^?1) of Zn or Pb. Maize was planted and grown for 42 days. At harvest, plants samples were analyzed for Zn and Pb concentration. Soils samples were analyzed for pH, extractable and diethylene triamine pentaacetic acid (DTPA) extractable Zn and Pb. Extractable Zn and Pb was lower in PBG compost amended soils than in unamended soils and steadily declined with increasing amount of compost applied. The extractable fraction for Zn dropped by 62.2, 65.0 and 44.6% for 300, 600 and 1200 mg Zn kg^?1, respectively when 200 t ha^?1 of PBG compost was applied. Metal uptake by maize plants were directly related to the rate of applied heavy metal ions with greater concentrations of metals ions found where metal ions were added to non-amended soils.     

Changes in phosphorus fractions in the rhizosphere of some crop species under glasshouse conditions

The aim of the present study was to evaluate the effect of cultivation of some agronomic plant species on inorganic soil‐P fractions in different sampling zones. The experiment was conducted as a completely randomized design as factorial in three replicates. The factors were plant species (10 different species and control) and soil‐sampling zone (soil adhering to root mat, rhizosphere soil, and nonrhizospheric soil). The thin‐slicing technique was modified and used to sample rhizosphere soil. The percentages of P fractions in the planted and control soils were near 64% apatite (apatite‐P), 24% octa‐Ca‐phosphates (OCP‐P), 7% Fe‐phosphates (Fe‐P), 4% di‐Ca‐phosphates (DCP‐P), 1% Al‐phosphates (Al‐P), and 0% occluded‐P (O‐P). All of the studied plant species decreased significantly all of the inorganic P fractions in soil adhering to root mat and in rhizosphere soil compared to those in nonrhizosphere soil. However, these decreases were not equal for each fraction and the percentage of apatite‐P increased in rhizosphere soil of the plant species. The means of total P, soluble P, DCP‐P, OCP‐P, Al‐P, and Fe‐P were lower in soil adhering to root mat compared to those in rhizosphere soil. However, this difference was only significant for OCP‐P. In contrast, the mean of apatite‐P in soil adhering to root mat was significantly higher than that in rhizosphere soil. The changes of apatite‐P may be more governed by microbial activities (especially mycorrhizal symbiosis) which may be higher in rhizosphere soil compared to soil adhering to root mat.     

Effect of soil heating on the dynamics of soil available nutrients in the rhizosphere

The effect of soil heating on the dynamics of soil available nutrients in the rhizosphere was evaluated. A pot experiment was carried out by using a rhizobox; a pot which enables to sample soils and soil solutions not only temporally with plant growth but also spatially depending on the distance from the root-accumulating compartment. The experiment consisted of 4 treatments; soils with or without heating treatment (150°C, 3 h), each of which was either planted with maize (Zea mays L.) or not. During the 17-d experiment, soil solutions at 0–2 mm from the root-accumulating compartment were collected 5 times. Soils depending on the distance from the root-accumulating compartment and plants were also collected after the experiment. The ionic concentrations of the soil solutions and soil water extracts, and the nutrient contents of plants were analyzed. Immediately after soil heating, the concentrations of cations, SO₄ ^2-, CI^-, water-soluble P, and water-soluble organic carbon increased significantly. With plant growth, the total ionic concentration in the rhizosphere soil solution increased for heated soil, whereas it decreased for unheated soil. The increase of the concentrations of cations and SO₄ ^2- in the rhizosphere of heated soil was appreciable, suggesting that the movement of cations such as Ca²⁺ and Mg²⁺ by mass flow was regulated by that of SO₄ ^2-. Moreover soil heating inhibited nitrification, resulting in the supply of N mainly in the form of NH₄ ⁺ within 10 mm from the root-accumulating compartment. As a result, the soil pH decreased in the rhizosphere of heated soil. The amount of nutrients absorbed by plants, on the other hand, did not change significantly by soil heating except for an increase of P uptake. The increase of P uptake could be explained not only by the immediate increase of the water-soluble P concentration but also by the dissolution of Ca-bound P and the hydrolysis of water-soluble organic P in the rhizosphere.     

Persistence of hexachlorocyclohexane isomers in soil planted with rice and in rice rhizosphere soil suspensions

Summary The relative persistence of -, and -isomers of hexachlorocyclohexane (HCH) was studied in a flooded soil with and without rice seedlings under greenhouse conditions. -HCH was more stable than - and -HCH in both planted and unplanted systems. - and -HCH decreased to negligible levels (5.5% for the -isomer and 2.4% for the -isomer) after 30 days in planted and unplanted soils. During the same period, 30.9% of the added -HCH was recovered from planted soil and 50.6% from unplanted soil. Likewise, in anaerobically (H₂ + CO₂ atmosphere) incubated mineral salts solution inoculated with suspensions from rice rhizosphere and non-rhizosphere soils, -HCH decreased to low levels (< 15%) within 5 days. Most of the added -HCH was recovered from mineral solution inoculated with nonrhizosphere soil suspension even after 30 days while -HCH decreased to 53.6% of the original level in mineral solution inoculated with rice rhizosphere soil suspension. The data reveal that the degradation of anaerobically unstable HCH isomers is not retarded by the possible aeration of a flooded soil by rice roots.     

Influence of the sunflower rhizosphere on the biodegradation of PAHs in soil

Reduced bioavailability to soil microorganisms is probably the most limiting factor in the bioremediation of polycyclic aromatic hydrocarbons PAH-polluted soils. We used sunflowers planted in pots containing soil to determine the influence of the rhizosphere on the ability of soil microbiota to reduce PAH levels. The concentration of total PAHs decreased by 93% in 90 days when the contaminated soil was cultivated with sunflowers, representing an improvement of 16% compared to contaminated soil without plants. This greater extent of PAH degradation was consistent with the positive effect of the rhizosphere in selectively stimulating the growth of PAH-degrading populations. Molecular analysis revealed that the increase in the number of degraders was accompanied by a dramatic shift in the structure of the bacterial soil community favoring groups with a well-known PAH-degrading capacity, such as Sphingomonas (α-Proteobacteria), Commamonas and Oxalobacteria (β-Proteobacteria), and Xhanthomonas (γ-Proteobacteria). Other groups that were promoted for which degrading activity has not been reported included Methylophyllus (β-Proteobacteria) and the recently described phyla Acidobacteria and Gemmatimonadetes. We also conducted mineralization experiments on creosote-polluted soil in the presence and absence of sunflower root exudates to advance our understanding of the ability of these exudates to serve as bio-stimulants in the degradation of PAHs. By conducting greenhouse and mineralization experiments, we separated the chemical impact of the root exudates from any root surface phenomena, as sorption of contaminants to the roots, indicating that sunflower root exudates have the potential to increase the degradation of xenobiotics due to its influence on the soil microorganisms, where sunflower root exudates act improving the availability of the contaminant to be degraded. We characterized the sunflower exudates in vitro to determine the total organic carbon (TOC) and its chemical composition. Our results indicate that the rhizosphere promotes the degradation of PAHs by increasing the biodegradation of the pollutants and the number and diversity of PAH degraders. We propose that the biostimulation exerted by the plants is based on the chemical composition of the exudates.     

Bioavailability of DOC in leachates, soil matrix solutions and soil water extracts from beech forest floors

The biodegradability of dissolved organic carbon (DOC) in different fractions from the forest floor was studied. Soil leachate (SL, the soil solution in macropores which is freely drained from forest floor after rainfall), the soil matrix solution (SMS, the soil solution in meso-/micropores of the soil matrix), and soil water extracts (SWE) from two different beech forest floors were compared. Zero-tension and tension lysimeters were used to collect SL and SMS, respectively. Loss of DOC (during 21 days) and respiration of CO₂-C (during 7 days) were used as conventional measures of the availability of DOC. Bacterial production, measured using the leucine incorporation technique, and bacterial growth efficiency were also estimated. All methods were used to study differences in biodegradability between plots with and without ground flora (Deschampsia flexuosa or Anemone nemorosa) and different type of forest floor (with an organic (O) horizon or a mull (A) horizon). There were no differences in bioavailability of DOC from soil solutions extracted from plots with and without ground flora. The bioavailability of DOC in the different collected soil solutions varied, however. DOC in SWE was the most available, with a mean of 39% of DOC-loss in 21 days, and 18% of DOC being respired in 7 days. DOC in soil matrix solution was the least available of the soil solutions (7% respired), significantly less than DOC in soil leachate (11% respired). The methods measuring biodegradation of DOC, DOC-loss and CO₂-C respiration gave similar results and were comparable to bacterial production and bacterial growth efficiency, with the exception of SWE from the O-horizon at the D. flexuosa site, which had low bacterial production and bacterial growth efficiency, indicating a limitation of the bacterial growth. This study is one of the first to use bacterial production and bacterial growth efficiency for measuring bioavailability in terrestrial environments, giving an extra dimension for the process of biodegradation of DOC.     

Effect of rice plant growth on denitrification in rhizosphere soil

The effect of rice plant growth on the loss of basal nitrogen (N) through denitrification in the rhizosphere of subsurface soil was investigated by the ¹⁵N balance method. Labeled ¹⁵N was applied to the deep soil layer to distinguish between the N losses in the surface and subsurface soils. Denitrification in pots with whole plants (Control) was compared with that in pots with plants cut off at the base of the culm (Pcut) to evaluate the effect of plant growth on denitrification. The upward movement of the applied ¹⁵N from the deep soil was negligible. Thus, the amount of unrecovered ¹⁵N was equal to the amount of N lost through denitrification in the rhizosphere of the subsurface soil (20–150 mm soil depth). In the Control treatment, values of redox potential at 50 and 90 mm soil depths were negative throughout the experimental period. Therefore, it was assumed that the redox potential could not have been the limiting factor for the N loss through denitrification in this experiment. The α-naphthylamine-oxidizing activity of roots decreased drastically after the cutting treatment. The estimated amount of de nitrified ¹⁵N in the rhizosphere of the subsurface soil was significantly higher in the Pcut treatment than in the Control one at 30 and 40 d after transplanting (DAT), while it was comparable in the two treatments at 52 and 64 DAT. Since a greater amount of ¹⁵N loss was found to occur when there was no absorption of ¹⁵N by the plants, the absorption of ¹⁵N by plants may have contributed to the suppression of denitrification. The amount of immobilized ¹⁵N in the Control treatment was larger than that of the Pcut treatment throughout the experiment. N immobilization might have also contributed to the suppression of denitrification in the rhizosphere of the subsurface soil.     

Zn和ABT对玉米根系生长及根际磷酸酶活性和pH的影响

在石灰性土壤上,以田间根袋栽培方法,研究了Zn和生根粉4号(ABT)对玉米在5个生育期中根系生长和根际微生态环境的影响。结果表明,玉米根系生长随生育期呈"S"型分布,根长和根体积在生育后期呈下降趋势。Zn和ABT的应用促进了根系的生长,扩大了根系和土壤接触面积,减缓了后期根系衰老速度,并改善了根际微生态环境。玉米根际土壤pH低于非根际;根际土壤磷酸酶活性显著高于非根际。抽雄期,Zn、ABT和Zn+ABT处理土壤碱性磷酸酶活性较高。Zn和ABT的应用改善了玉米根际微生态环境,为有效利用土壤和肥料磷打下基础。     

Mechanisms of potassium uptake efficiency and dynamics in the rhizosphere of safflower and sunflower in different soils

Potassium uptake efficiency of safflower and sunflower was studied under semi-controlled conditions in loamy and sandy soils. Both species performed better in loamy soil. Safflower had higher agronomic efficiency and higher relative root length under suboptimal K supply. Safflower had higher specific root density and less root radius at all K levels. Safflower had higher relative root-shoot ratio under suboptimal K in loamy soil. Both species had similar K-influx at low and optimal K in loamy soil, while sunflower had higher influx under suboptimal and optimal supplies in sandy soil. Safflower had higher shoot demand in both soils under suboptimal and optimal K. Both species depleted similar amounts of soil solution-K under suboptimal K in sandy soil, while sunflower was more efficient under suboptimal levels in loamy soils. Sunflower depleted more extractable-K under both suboptimal and optimal K. Safflower could be considered K-uptake efficient crop.     

双孢蘑菇菌糠对小白菜生长及根际土壤的影响

采用田间试验,研究不同施肥对小白菜生长及土壤速效磷转化的影响.结果表明,施用未灭菌双孢蘑菇菌糠肥料处理能有效促进小白菜的生长,其根长、叶片数、茎长、鲜重分别比未施肥对照组高16.7%、27.7%、20.1%、29.5%;可明显改善小白菜根际的微生态环境,土壤中细菌数量较未施肥对照组增加39.7%,放线菌的数量增加18%;加快根际土壤速效磷的转化,较未施肥对照组增加了0.40%.     

Are the links between soil aggregate size class, soil organic matter and respiration rate artefacts of the fractionation procedure?

Our aim was to see how variations in aggregate fractionation procedures influence the chemical and biological properties of different sized soil aggregates. Soil was fractionated using two different physical procedures: (1) slaking to simulate a major wetting stress in the field or (2) shaking to simulate mechanical disruption by tillage followed by wet sieving. In the slaked treatment, macro-aggregates (<250 μm dia) contained about 17% more soil organic C and had about 30% faster rates of respiration. This was in contrast to the shaken treatment where micro-aggregates (<250 μm dia) contained about 12% more soil organic C and had about 14% faster rates of respiration. The biological and chemical properties of different sized aggregates were used to describe two different models. These were the aggregate heirarchy model and one based on maximum biological activity at soil surfaces. Our results suggest that the chemical and biological properties of aggregates depend on the fractionation procedure. On this basis we suggest that the observed relationships between aggregate size and other properties, for example biological activity, must be interpreted in terms of the disruptive mechanisms used to fractionate aggregated soil. Our results suggest that the aggregate hypothesis has serious weaknesses: the aggregates measured being largely an artefact of the chosen method of separation. We therefore suggest that future work should also consider biological activities at soil pore surfaces. It is at the surface of these channels that parameters such as oxygen supply, plant roots, root exudates and fresh organic matter inputs first interact with the soil. Biological processes in this region are therefore likely to be more important than those occurring in the bulk soil.     

宁波市辖区水稻土硅钙镁锌铜有效性评价及其影响因素研究

研究分析了宁波市辖区(江北、镇海、北仑)水稻土耕层中的有效Si、Ca、Mg、Zn、Cu含量及其影响因素。结果表明,研究区内土壤有效硅、有效钙、有效镁、有效锌和有效铜均属中等变异强度,变异系数介于27.6%~71.1%,有明显缺硅、缺铜现象。相关分析表明,各元素有效含量与土壤有机质含量呈一定正相关性;有效硅、有效钙、有效镁与土壤pH呈极显著正相关性,有效锌和有效铜与土壤pH呈一定负相关性。因此,在一定程度上,土壤有机质和pH水平可以反映出有效Si、Ca、Mg、Zn、Cu含量的丰缺程度。     

农林复合杨树土壤养分的根际效应

用对比试验的方法,研究农林复合中杨树+留兰香、杨树+小麦、杨树+红薯和杨树纯林4种林地的杨树生长量、林地土壤物理性状和土壤养分以及杨树和间作物养分的根际效应。结果表明:1)杨树+留兰香林地的杨树生长量明显小于对照,显著小于杨树+小麦和红薯林地;2)间作林地的土壤物理性状、土壤pH值、非根际土壤养分不是影响杨树生长的关键因素,而根际土壤养分及根际效应的变化对杨树生长有直接影响;3)在杨树根际土壤中,杨树+小麦和红薯林地杨树根际土壤养分质量分数均高于对照;杨树+留兰香林地的杨树根际土壤有机质和速效磷质量分数高于对照,速效钾和速效氮质量分数则低于对照,而留兰香的根际养分质量分数除速效氮外均高于小麦和红薯;4)从养分的根际效应来看,杨树+留兰香林地杨树的养分根际效应值除有机质外小于对照并小于留兰香,杨树+小麦林地杨树的养分根际效应值除速效磷外均大于对照并大于小麦,杨树+红薯林地杨树的养分根际效应值除速效磷外均小于对照,除速效氮外均大于红薯。     

改性磷矿粉在石灰性土壤上的生物有效性及其机理研究

为缓解磷资源危机,充分利用不适于化学加工的磷矿资源,对磷矿采用活化技术开发利用,由此生产的改性磷肥已被证明在酸性土壤上有很高的生物有效性,但在石灰性土壤上的研究还比较少。本文选择4种不同产地(云南昆明、四川德阳、四川绵竹和贵州开阳)的磷矿粉,分别用有机活化剂和无机活化剂进行活化处理,制备改性磷矿粉,并就其在石灰性土壤对苗期春小麦的生物有效性进行了盆栽试验。结果表明,4种磷矿粉经活化处理后有效磷和水溶性磷含量均明显增加,无机活化剂提高了有效磷的含量,而有机活化剂对水溶性磷的提高幅度较大。改性磷矿粉处理均不同程度提高了石灰性土壤上春小麦的生物量干重、植株吸磷量和磷利用效率,有机活化剂处理制备的改性磷矿粉对春小麦生长的促进作用更为明显。运用红外光谱谱学技术对4种磷矿粉及相应的8种改性磷矿粉结构分析结果表明,磷矿粉经改性后其结构发生了明显变化,H2PO4和HPO42的特征谱带明显增加,增加的程度因磷矿粉的产地和活化剂种类不同而有差异。对磷矿粉化学成分分析结果表明,不同产地的磷矿粉其磷以及钙、铁、铝、镁等化学成分的含量差异较大,活化剂对磷矿粉的活化效果与磷矿粉本身的氧化物含量有关。在本试验条件下,磷矿粉Ⅲ(四川绵竹)的活化效果相对最好,与其氧化镁含量最高、总氧化物含量最低有关。不同类型活化剂对磷矿粉的活化效果不同,红外光谱分析结果表明,无机活化剂活化效果较好,而土培试验结果表明有机活化剂的活化效果较好,这一结果有待进一步的研究。     

不同树龄茶树根际土壤酶活性的变化分析

以不同种植年限黄金桂茶树根际土壤为研究对象,分析茶树树龄对土壤酶活性的影响。结果表明,茶树根际土壤中与养分循环相关的酸性磷酸酶、脲酶、蔗糖酶活性随着茶树树龄的增加而上升,且与茶树树龄呈显著正相关,中性磷酸酶、碱性磷酸酶则相反;茶树根际土壤中与抗性相关的多酚氧化酶活性随着茶树树龄的增加而上升且与茶树树龄呈显著正相关,而过氧化物酶、过氧化氢酶、脱氢酶活性则呈下降趋势,与茶树树龄呈显著负相关。土壤酶对茶树树龄的敏感性分析结果表明,不同土壤酶响应茶树树龄变化的趋势为过氧化氢酶脲酶脱氢酶蔗糖酶过氧化物酶多酚氧化酶酸性磷酸酶中性磷酸酶碱性磷酸酶。可见,在茶树生产管理过程中应适当提高磷肥的施用量,老茶树应当加强土壤松耕,以提高土壤中抗性酶活性。     

黑土根际土壤有机碳及结构对长期施肥的响应

由于人类农业措施的干扰,氮肥和畜禽粪污大量输入到黑土中,对土壤有机碳库产生了较大负面影响。根际有机碳在调控土壤碳循环和养分转化中发挥着重要的作用。探明根际有机碳对不同养分的生态响应,可为不同施肥处理下黑土农田生态系统碳固持和农田可持续利用提供理论依据。该研究以黑土长期定位试验为基础,采集长期不施肥（CK）、常量氮（N）、二倍量氮（N2）、常量有机肥（M）、二倍量有机肥（M2）、常量有机肥+常量氮（MN）、二倍量有机肥+二倍量氮（M2N2）7个处理下大豆根际土壤,分析了根际有机碳和活性有机碳特征,同时利用固态核磁共振技术分析其光谱特征。结果表明,N、M2、MN和M2N2处理的根际土壤有机碳含量显著高于非根际水平,且以MN和M2N2处理的根际效应最显著,分别比非根际增加了18.3%和26.7%。分析核磁共振光谱显示,与非根际土壤相比,根际土壤具有较高的烷氧基碳比例和较低芳香碳比例,表明根际效应能够改变土壤有机碳结构比例。与不施肥处理相比,大部分施肥处理提升了黑土根际有机碳含量,其中以氮肥马粪配施和二倍量马粪（M2N2）处理提升幅度最高。由核磁共振图谱可知,M2和M2N2处理均增加根际土壤难降解成分烷基碳比例、芳香基碳比例、烷基碳与烷氧基碳比值、芳香碳与总碳比值,而MN处理仅增加烷基碳比例、烷氧基碳比例以及烷基碳与烷氧基碳比值。二倍量氮肥（N2）处理降低烷基碳比例、芳香碳比例和烷氧基碳比例,根际土壤难降解成分降低,不利于土壤固碳,同时证明固态 13C-核磁共振技术结合半定量分析能够准确地分析不同有机碳结构组分变化,深刻认识根际土壤有机碳的稳定机制。     

施肥对I-107杨树人工林土壤根际效应的影响

 通过研究施用有机肥、化学肥料和生物菌肥对I-107杨树人工林根际和非根际土壤微生物数量和土壤酶活性的影响,分析土壤酶活性与土壤微生物数量的关系。研究结果表明:不同种类肥料使用后3个月,林地根际土壤和非根际土壤微生物总量均有显著增长,其中有机肥处理土壤微生物数量增长幅度最大,菌肥处理最小。施肥处理显著提高土壤脲酶、碱性磷酸酶、过氧化氢酶、过氧化物酶活性,但尿素和菌肥处理土壤多酚氧化酶活性降低。施用有机肥处理对土壤微生物和土壤酶根际效应值影响最明显,菌肥处理影响最小。尿素处理土壤pH值高于对照,有机肥和菌肥处理小于对照,但不同处理间土壤pH值的根际效应值差异性不明显。土壤微生物数量与土壤酶活性之间存在一定的相关性,其中:土壤脲酶活性与好气性纤维素分解菌之间、土壤碱性磷酸酶活性与氨化细菌、真菌、放线菌、亚硝酸细菌之间,土壤过氧化氢酶与好气性纤维素分解菌、真菌、放线菌之间相关性显著。