外加碳酸盐增加石灰性土壤密闭培养过程中CO2的释放量

The closed-jar incubation method is widely used to estimate the mineralization of soil organic C. There are two C pools (i.e., organic and inorganic C) in calcareous soil. To evaluate the effect of additional carbonates on CO2 emission from calcareous soil during closed-jar incubation, three incubation experiments were conducted by adding different types (CaCO3 and MgCO3 ) and amounts of carbonate to the soil. The addition of carbonates significantly increased CO2 emission from the soil; the increase ranged from 12.0% in the CaCO3 amended soil to 460% in the MgCO3 amended soil during a 100-d incubation. Cumulative CO2 production at the end of the incubation was three times greater in the MgCO3 amended soil compared to the CaCO3 amended one. The CO2 emission increased with the amount of CaCO3 added to the soil. In contrast, CO2 emission decreased as the amount of MgCO3 added to the soil increased. Our results confirmed that the closed-jar incubation method could lead to an overestimate of organic C mineralization in calcareous soils. Because of its effect on soil pH and the dissolution of carbonates, HgCl2 should not be used to sterilize calcareous soil if the experiment includes the measurement of soil CO2 production.     

蜡样芽孢杆菌菌株X5强化的生物有机肥能有效控制根结线虫(Meloidogyne sp.)

The efficacy of Bacillus cereus X5 as a potential biological control agent against root-knot nematodes was evaluated in vitro by examining second-stage juvenile mortality and egg hatching rate under addition of culture filtrate and in planta by application of bio-organic fertilizers enhanced with B. cereus X5, B. thuringiensis BTG, or Trichoderma harzianum SQR-T037 alone or together in greenhouse and field experiments. The biofumigation of the root-knot nematode-infested soil with organic materials (chicken manure, pig manure and rice straw) alone or in combination with B. cereus X5 was also conducted in greenhouse experiments. In laboratory, the filtrate of B. cereus X5 more effectively reduced egg hatching rates during the incubation period for 14 d and more effectively killed the second-stage juvenile during the incubation period of 24 h than that of B. thuringiensis BTG. The highest dry shoot weights for greenhouse tomatoes and field muskmelons were found in both the treatment consisting of the bio-organic fertilizer enhanced with the three biocontrol agents and the treatment consisting of the bio-organic fertilizer enhanced only with B. cereus X5. The two bio-organic fertilizers achieved better nematicidal effects than those enhanced only with B. thuringiensis BTG or T. harzianum SQR-T037. B. cereus X5 also enhanced effect of biofumigation, which resulted in increased plant biomass and reduced nematode counts in the roots and rhizosphere soil. Therefore, these results suggested that biological control of root-knot nematodes both in greenhouses and fields could be effectively achieved by using B. cereus X5 and agricultural wastes.     

再氧化对土壤的通气性变异的影响

The interplay between soil physical parameters during the recovery from anoxic stresses (reoxidation) is largely unrecognized. This study was conducted to characterise the soil aeration status and derive correlations between variable aeration factors during reoxidation. Surface layers (0-30 cm) of three soil types, Haplic Phaeozem, Mollic Gleysol, and Eutric Cambisol (FAO soil group), were selected for analysis. The moisture content was determined for a range of pF values (0, 1.5, 2.2, 2.7, and 3.2), corresponding to the available water for microorganisms and plant roots. The variability of a number of soil aeration parameters, such as water potential (pF), air-filled porosity (Eg), oxygen diffusion rate (ODR), and redox potential (Eh), were investigated. These parameters were found to be interrelated in most cases. There were significant (P < 0.001) negative correlations of pF, Eg, and ODR with Eh. A decrease in water content as a consequence of soil reoxidation was manifested by an increase in the values of aeration factors in the soil environment. These results contributed to understanding of soil redox processes during recovery from flooding and might be useful for development of agricultural techniques aiming at soil reoxidation and soil fertility optimisation.     

紫色土坡耕地土壤团聚体分形维数与有机碳关系

为深入理解有机碳对土壤团聚体的影响,采用干筛法和重铬酸钾外加热法并基于相关分析研究了不同施肥处理紫色土耕地土壤团聚体分形维数（D）与有机碳（SOC）的关系。结果表明：不同施肥处理和土层间 D 与SOC均存在差异,变化范围分别为2.376～2.603、3.54～12.07 g/kg,均值都随土层变深呈递减趋势。全样本（n=36,不区分处理和土层）中D与SOC显著相关,但并非简单相关。进一步对D与各粒级有机碳含量（fSOC）的相关分析表明,在全样本中二者相关性显著,且随粒级的减小相关程度变大。不同施肥处理和土层间的相关分析中二者相关性又表现不同：除对照CK,其他处理的呈现多组显著相关,耕作层（0～20 cm）多组的相关性都很微弱,而犁底层（＞20～30 cm）的多个组却显著相关。分析认为,这与不同施肥处理所提供的碳源在团聚体形成过程中所起作用的差异有关,该差异将使团聚体形成各自的特点从而表现出各自的分形特征;并且D与fSOC相关性的差异是团聚体中大小颗粒间结构相似程度的反映,体现出各级团聚体在形成过程中的主导因素是否具有一致性,表明该相关关系对形成土壤结构的主导影响因素具有表征作用。该研究结果有助于深入认识和理解土壤团聚体分形维数的影响因素、物理意义以及对土壤结构的表征性。     

丘陵旱地红壤上施用硼、锌和钼肥对紫云英种子产量的影响

通过田间试验,研究了施用硼、锌和钼肥对紫云英种子产量、根瘤菌数量的影响。结果表明:与不施硼、锌和钼肥处理相比,施用硼、锌和钼肥处理的紫云英种子产量提高13.7%～38.9%,且差异均显著(P<0.05);主要因单株结荚数和每荚种子粒数等产量构成因素提高,施用硼、锌和钼肥处理的单株结荚数和每荚种子粒数分别提高18.9%～44.3%和21.4%～33.3%,均达显著差异(P<0.05)。施用硼、锌和钼肥可以促进紫云英根瘤的形成,施用硼、锌和钼肥处理紫云英根瘤数增加2.1%～82.4%。施用钼肥处理紫云英的种子产量、经济性状和根瘤数量均高于未施钼肥处理。说明紫云英生长发育及种子产量形成对钼的敏感性高于其它微肥种类。     

Experimental Investigation of Stabilized Soft Soil by New GSC

Soft clay is stabilized by desulphurization gypsum and steel slag-slag blended cementitious materials (GSC), which can not only reuse industrial waste and decrease second pollution, but also can conserve mineral resources and protect natural ecology. The variation of unconfined compressive strength of the clay improved by GSC with different mixing ratios and water-GSC ratio and ages was studied through the laboratory experiments. The long-term strength of stabilized soil is predicted with GSC by quasi-water-GSC ratio. The results show that the more the mixing ratios is, the better the stabilized effect of soft soil is. With increase of curing period, the strength increasing of GSC-soil is consistent with cement-soil, and it has lower strength in the early stage. When mixing ratios of GSC is more than those of cement by 3%, if the water-GSC ratio is less than those of cement, it has the higher strength than cement-soil, after 28 days. The results show that GSC stabilized soil is feasible and it can meet the demand of cure strength.     

稻麦轮作周年氮磷运筹对作物产量和土壤养分含量的影响

通过稻麦轮作两周年四季作物的田间小区试验,研究了氮磷减量及磷肥运筹对水稻、小麦产量和第二周年稻麦收获后土壤养分含量的影响。结果表明:在习惯施肥的基础上减少氮肥用量10.8%和磷肥25.0%,对第一周年小麦、水稻产量和第二周年小麦产量没有显著影响,却显著降低了第二周年水稻产量;氮磷减量处理显著降低了第二周年水稻收获后土壤有效磷的含量,而对土壤pH值、有机质、碱解氮和速效钾含量没有显著影响;在氮磷减量条件下,小麦、水稻两季均施用磷肥与小麦一季集中施用磷肥进行比较,二者之间两周年四季作物产量没有显著差异。据此,建议稻麦轮作区实施\"氮肥适当减量、磷肥隔年集中施用在小麦季\"的氮磷施肥原则,可以达到降低肥料用量和劳动力投入,同时保证产量的目的。     

直槽沟填式刚性管道土压力计算

针对直槽沟埋式刚性管道,建立了直线滑移面土压力计算模型,基于双剪统一强度理论,推导出了新的土压力计算公式｡与传统的土压力计算方法相比较,新的土压力计算方法可以考虑中间主应力对管道土压力的影响,土压力理论计算值更为接近管道的实际受力情况｡结合工程实例计算分析,揭示了开槽宽度､上覆土层厚度等对管顶土压力的影响规律｡所得结论,对管道工程的优化设计具有一定的指导意义｡     

热脱附处理技术对汞污染土壤的影响

研究温度和停留时间对含汞污染试样汞脱除率的影响,探讨不同形态汞在脱附处理过程中的浓度变化及转化规律。以青海、云南两地某氯碱生产废弃工厂汞污染土为试样,采用管式电阻炉对试样进行热脱附,使用连续浸提法提取分析7种形态汞。结果表明,从环境安全性、经济性考虑,采自青海、云南土样最佳的脱附温度和停留时间分别为 300 ℃和60 min、500 ℃和30 min。各形态汞在脱附过程中发生转化,处理后土壤中汞主要以残渣态或晶格态存在,环境风险小。     

热带不同母质香蕉园土壤理化性状比较研究

通过对热带不同母质香蕉园土壤理化性状的分析,结果表明：①玄武岩母质发育的香蕉园土壤全钾含量比冲积土的低88.2%,有机质、全氮和全磷含量比冲积土的分别高86.1%,42.1 %和153.7%。②玄武岩发育的香蕉园土壤碱解氮和速效钾含量比冲积土的分别高124.5%和48.0%,速效磷减少32.1%。③玄武岩发育形成的土壤脲酶、酸性磷酸酶、蔗糖酶和过氧化氢酶活性比冲积土的分别高20.3%、121.0%、122.2%和11.9%。④热带香蕉园土壤速效磷和速效钾含量出现明显富集现象,玄武岩和冲积土发育形成的香蕉园土壤速效磷分别比对照土壤提高了1124%和602.9%;土壤速效钾含量分别比对照的提高了502.9%和255.8%。