Organic Sulfur and the Retention of Nutrient Cations in Forest Surface Soils

Sulfur and cation transformations were studied in A-horizon soils from 9 plots in Deer Run State Forest (DRSF) in southeastern Missouri on two dates, and from 27 plots of the Missouri Ozark Forest Ecosystem Project (MOFEP) near DRSF, seasonally for three years. The DRSF plots were chosen based on history of timber harvest; 2-3 yr and 8-10 yr post clear-cut, with controls about 40 yt post cut. Total C and S, organic sulfur (OS), exchangeable K+ and Mg2+, and rates of microbial OS production varied by season and year in surface soils from MOFEP plots. Exchangeable K+ concentrations were correlated with total C, total S, and OS. In clear-cut DRSF A-horizon soils, OS production was greatly reduced (p < 0.05) compared with controls. Exchangeable K+ and Mg2+ also were much lower in soils from clear-cut plots than in soils from control plots (p < 0.01). Cation exchange for OS compounds with sulfhydryl groups was only marginally greater than for organic matter of similar structure with no sulfhydryl groups. Overall, litter input appears to be a key to maintaining long-term surface soil OS, K+, and Mg2+ concentrations.     

砂壤土上甘蔗管理的土壤质量指示评估

An important factor for the sustainability of soils highly susceptible to degradation is the use of monitoring tools that promptly and realistically reflect changes imposed on soil by different cropping systems. To select soil quality indicator variables in sugarcane (Saccharum officinarum L.) production areas that fulfill the criteria of sensitivity to management practices and between-season consistency in the management discrimination, ten composite soil samples (0-10 cm) were collected in July 2005 (rainy season) and again in March 2006 (dry season) from areas under cultivation of organic sugarcane (OS), green sugarcane (GS), burned sugarcane (BS) and from an adjacent native forest (NF) area at Usina Triunfo, Boca da Mata, Alagoas, Brazil. Microbial biomass-C (MBC), total organic C (TOC), soil enzyme activity expressed as the rate of fluorescein diacetate (FDA) hydrolysis, mean weight diameter of water-stable soil aggregates (MWD), and percentage of water-stable macroaggregates (PWSA) were analyzed. Although MBC and TOC were higher in NF than in the cultivated areas, no differences were observed in these C pools between the three sugarcane systems. The response of FDA to the site management was dependent on the sampling time. In the rainy period, the activity followed the order: NF > OS > GS > BS, whereas in the dry season, only NF differed from the other treatments. Irrespective of the sampling time, MWD and PWSA decreased in the order NF > OS = GS > BS. The variables MWD and PWSA are quite sensitive for discriminating between site management histories regardless the sampling season.     

长期不同施肥下紫色土有机硫和芳基硫酸酯酶活性变化特征

  【目的】  基于长期定位试验，探究施入含硫肥料的不同处理土壤总硫与有机硫含量变化，以及不同施肥处理土壤总硫与有机硫的变化趋势，为硫素的合理施用提供理论依据。  【方法】  长期定位试验位于重庆市北碚区西南大学国家紫色土肥力与肥效监测基地，始于1991年，至本研究取样时已连续进行了22年，一年两季，水稻?小麦轮作。选择试验中的7个处理:不施肥 (CK)，施用氮磷钾 (硫酸钾，NPK_S)，有机肥单施 (M)，氮磷钾配施有机肥 (MNPK_S)，氮磷钾与稻草还田配合施用 (SNPK_S)，含氯化肥氮 (氯化铵)、磷、钾 (氯化钾) 与秸秆还田配施 (SNPK_Cl)和永久休闲 (F)。取0—20 cm土样，测定了全硫、有机硫以及3种形态有机硫含量以及芳基硫酸酯酶活性。  【结果】  1) 与1991年原始土壤相比，除CK的全硫和有机硫含量显著降低外，其余处理均显著增加，且土壤全硫含量除M和NPK_S处理间差异不显著外，其他处理间均差异显著，由高到低为MNPK_S > SNPK_S > M和NPK_S > F > SNPK_Cl。土壤有机硫在全硫中的占比也发生了变化，CK处理中有机硫含量显著下降，其他处理均显著增加 (P < 0.05)。MNPK_S和SNPK_S处理有机硫含量增加最多，但是MNPK_S处理有机硫在全硫中的占比只有73.3%，而SNPK_S为92.2%。另外，M和F处理有机硫含量差异不显著，但都显著高于SNPK_Cl和NPK_S处理 (P < 0.05)。SNPK_Cl处理的有机硫含量虽然显著低于MNPK_S、SNPK_S、M和F处理，但有机硫的占比 (90.3%) 与SNPK_S处理相当，而NPK_S处理的有机硫含量虽然高于CK和初始土壤，但显著低于F处理和含有机肥处理的土壤 (P < 0.05)。2) 与CK相比，其他施肥处理0—20 cm土层中碳键硫、酯键硫、残渣态硫含量均有所增加，且不同施肥处理之间差异达到显著水平。与初始土壤相比，包括F在内的所有处理中碳键硫和酯键硫含量增加，其中MNPK_S处理的碳键硫的增加量显著高于其他处理，增加了31.1 mg/kg；酯键硫增加量最大的处理是SNPK_S，增加了37.05 mg/kg；而残渣态硫除MNPK_S处理增加了52.2 mg/kg和F处理增加了11.65 mg/kg外，其余处理均减少，以CK减少最多 (46.62 mg/kg)。3) 与初始土壤相比，土壤芳基硫酸酯酶的活性除SNPK_Cl处理减少了 8.19 μg/(mL?h)和F处理减少了7.80 μg/(mL?h)外，其余处理都有不同程度的增加，增加最大的处理是SNPK_S，增加了37.77 μg/ (mL?h)，其次是M处理，增加了33.91 μg/ (mL?h)。  【结论】  长期施用化肥、有机肥、化肥与有机肥配施都显著增加了紫色土壤有机硫中碳键硫、酯键硫的含量，降低了残渣态硫含量，因而显著提高了硫的有效性。不施肥，不论是否休闲，均降低土壤中有机硫的有效性。含氯化肥也能提高土壤硫的有效性，并且含氯化肥与有机肥配合施入土壤，一定程度上提高了有机硫的比例。但长期施用含氯化肥会降低芳基硫酸酯酶活性，在施肥的时候尤其是长期施入含氯化肥，应该密切关注土壤中pH的变化问题。     

Chemical and microbiological soil properties in organic and conventional management systems of Coffea arabica L.

The goal of this study was to evaluate the effect of organic (OS) and conventional (CS) farming of Arabica coffee on chemical and microbiological soil properties and to identify which attributes correlate and/or contribute to distinguishing these two management systems. We collected soil samples on a 100 × 100 m² grid in both, the OS and CS, in winter and summer and submitted chemical and microbiological properties to univariate and multivariate analyses (canonical discriminant analysis – CDA – and redundancy analysis – RDA). The best indicators to discriminate OS and CS were chemical and microbiological properties, as the elements calcium (Ca) and boron (B), besides microbial biomass carbon (MBC), metabolic quotient (qCO₂), acid phosphatase (ACP), and alkaline phosphatase (ALP). The RDA showed that, regardless of the season, MBC and ACP correlated with nitrogen (N), sulfur (S) and organic matter (OM), whereas basal respiration (C-CO₂) and ACP correlated with qCO₂ and with magnesium (Mg), calcium (Ca), phosphorus (P), potassium (K) and pH.     

Contaminant aspects of blackish surface deposits on highway roadsides

A blackish, sandy material (‘blackish deposit’, BD) accumulates on highway roadsides. Few years after road opening it may reach several centimeters of depth. Comparison of BD rates of accumulation with reported loads of suspended solids in highway runoff suggests blackish deposits to originate both from suspended solids in road runoff and from aerial depositions. This study of four Danish highways shows that BD is considerably different from the original surface (OS) material. Compared to OS-materials, BD-materials are clearly darker, contain more organic matter(4–8% versus around 1% in OS), have a high and less-variable content of clay and metal oxides, and a slightly lower bulk weight and pH. Similar clay mineralogy points to both BD and OS to be of local origin. Both materials contain lime (calcite). The textural border between BD and OS is also a sharp border between different levels of soil contamination: Zn up to 330 mg/kg in BD versus 19–63 mg/kg in OS, Pb up to 210 mg/kg versus 5–33 mg/kg, Cr up to 250 mg/kg versus 3–10 mg/kg, Cd up to twice as high in BD as in OS, Br and As markedly higher in BD than OS, heavy mineral oils (nC25–nC35) up to 680 mg/kg versus 16–24 mg/kg, and sum of PAH up to 1.4 mg/kg versus < 0.05–0.72 mg/kg. The continuous deposition of organic matter, calcite, metal oxides and clay suggest that BD, in addition to particles, is able to accumulate dissolved contaminants from infiltrating road runoff.     

设施种植模式对土壤细菌多样性及群落结构的影响

为了研究有机和常规设施种植模式及轮作对土壤细菌多样性和群落结构的影响,本研究采用Illumina平台Hiseq 2500高通量测序技术,于2016年6月(作物处于收获期)对北京市顺义区不同设施种植模式(分别为有机设施种植模式和常规设施种植模式下的叶菜连作、茄果连作和叶茄轮作)下土壤细菌进行16S r RNA测序。测序质控后共获得17 278个操作分类单元(operational taxonomic units,OTUs),共计318 851条有效序列。比较不同种植模式和轮作下土壤细菌多样性、细菌群落结构组成、相对丰度及土壤理化性质与细菌群落多样性关系的差异性。结果表明:土壤微生物群落结构在有机和常规设施种植模式下差异明显,有机设施种植土壤细菌多样性高于常规设施种植;有机设施种植下轮作与连作土壤细菌群落结构表现出明显差异,而常规设施种植下,两者没有明显差异;有机种植模式下,轮作土壤细菌群落多样性高于连作土壤;设施种植土壤细菌群落主要属于鞘氨醇单胞菌属(Sphingomonas,5.05%)和芽孢杆菌属(Bacillus,4.84%),相对丰度大于0.5%的共有14个属。有机设施种植土壤含有较多促进植物生长、有机质分解的细菌,常规设施种植土壤中降解化学杀虫剂、防治土壤病害、促进硝化过程的细菌较多。RDA分析结果显示土壤细菌群落主要受全磷、速效磷、有机质的影响。Tumebacillus、Candidatus Solibacter和Acidothermus都是分解有机质、利用碳源的细菌属,与土壤有机质含量呈正相关关系。由此可见,设施条件下,有机和常规种植土壤微生物群落结构的差异性主要源于肥料使用、有害生物防治措施和管理方式的不同。有机设施种植模式下,轮作更有利于发挥其改良土壤营养循环和防治土壤病虫害的作用。上述结果为在微生物水平上研究设施条件下不同种植模式的土壤生态质量差异提供了参考。     

有机肥质量分数对土壤导水率稳定性的影响

饱和导水率是水循环和土壤侵蚀模型中的重要参数,也是土壤结构改善的重要指标.通过室内土柱模拟实验研究有机肥添加量对风沙土和壤土导水率的影响.土壤添加有机肥的比例设置为0％、5％、10％、15％、20％、25％、30％7个水平,土壤密度设3个水平,各处理5个重复.结果表明：1）土壤饱和导水率随有机肥质量分数的增加呈降低趋势,风沙土的饱和导水率随有机肥质量分数的增加呈直线下降趋势,而壤土饱和导水率的降低趋势随有机肥质量分数的增加减缓;2）有机肥质量分数的增加对土壤密度的降低作用可以抵消有机肥增加导致的饱和导水率的降低;3）低土壤密度下土壤导水率随时间变化不稳定,土壤密度增大后随时间变化稳定.随着有机肥质量分数的增加,土壤导水率的测定过程趋于稳定,但是测定时间延长.     

中天山北坡垂直带土壤有机碳密度分布特征

以乌鲁木齐河流域为重点研究区,利用实测典型土壤剖面特征数据估算土壤有机碳密度,就剖面有机碳和表层有机碳之间,剖面有机碳、表层有机碳和海拔高度之间,土壤剖面有机碳密度与发生层深度之间以及不同土壤类型土壤有机碳密度的分布特征进行相关分析,结果表明:在中海拔区域,土壤有机碳的密度最大且含量最高。发生层越厚,土壤的发育程度就越高,土壤有机碳密度也就越大,有机碳的含量就越高。全剖面和表层土壤有机碳密度值分别为46.91,13.95 kg/m²。不同土壤类型的土壤有机碳密度存在着显著差异。     

黄土高原生态系统演替进程中土壤有机质和pH值变化规律

通过对黄土高原生态系统演替进程中土壤有机质和pH值变化进行分析,结果表明:在同一演替系列中,随演替进程的推移,土壤中有机质增加,pH值减小;在不同地段上,演替高级阶段土壤的有机质高于低级阶段,pH值正好相反;人为间断干扰的生态系统土壤有机质下降,pH值升高;人为持续干扰的亚顶级生态系统土壤有机质明显降低,PH值明显升高.     

乌鲁木齐河流域土壤有机碳与气候因子相关性研究

为了解土壤有机碳与气候因子的相关关系,对乌鲁木齐河流域6种不同土壤类型进行了研究,结果表明:土壤有机碳与水热指标之间呈现不同性质和程度的相关性,与降水指标呈较显著正相关,与各温度指标呈较显著负相关;不同土壤类型有机碳变化与水热指标间的相关关系呈现不同特征,相关程度虽有不同,但总体符合与降水正相关温度负相关的特征;通过人为控制研究区气温与降水指标条件进行偏相关分析,结果显示在控制温度的条件下降水增加有机碳含量可能减少;在控制降水的条件下温度升高有机碳含量可能增加。研究认为在未来较长时间序列,气候变化不会导致研究区土壤碳库容量大幅变化。     

长期定位施肥对无石灰性潮土酶活性的影响

试验研究长期定位施肥对无石灰性潮土酶活性的影响结果表明,长期单施有机肥及其配施无机化肥均能显著增强土壤脲酶、蛋白酶、磷酸酶和蔗糖酶的活性。土壤脲酶活性、蛋白酶活性与土壤有机质、全N、碱解氮含量呈极显著正相关,磷酸酶活性与土壤有机质、有机磷、有效磷呈极显著正相关,蔗糖酶活性与土壤有机质呈极显著正相关。表明土壤酶活性与土壤肥力密切相关,可作为评价土壤肥力性状的生物学指标。     

植物凋落物分解对土壤有机碳稳定性影响的研究进展

凋落物是植物向土壤输入有机碳的主要途径,源于凋落物的碳一部分以CO₂的形式散失到大气,另一部分以有机碳的形式输入到土壤中,在土壤微生物的作用下经过一系列的周转参与稳定有机质的形成。但土壤作为“黑箱”,凋落物向土壤有机碳转移的过程和作用机理仍不明确。结合国内外该研究领域的主要成果,简要介绍了植物凋落物分解的研究方法、土壤有机碳组分及土壤有机碳稳定性,并从植物凋落物分解对土壤有机碳及其组分、土壤呼吸和激发效应、土壤微生物群落结构及酶活性的影响以及植物-土壤-微生物相互作用过程对有机碳稳定性的影响等方面进行概述,厘清植物凋落物分解与土壤稳定有机碳形成的关系,并提出了未来该领域亟待关注的研究方向和研究内容。     

阴山北麓不同用地土壤有机质含量对抗风蚀的作用研究

随着人类对土地利用的强度不断增大,改变了自然土壤表层原有的性质,并对风产生不同的抗蚀效果。不同的土地利用方式下,土壤的有机质含量是不同的。土壤有机质影响土粒间微结构的胶结力和土壤结构体间的抵抗离散力,从而影响土壤的抵抗风蚀能力。通过对阴山北麓不同土地利用方式下的土地进行野外调查取样和室内理化分析,分析了土壤有机质含量变化过程,研究了土壤有机质含量对抗风蚀的影响。结果表明：土壤有机质含量与土壤抗风蚀强度成正相关关系,也就是随着土壤有机质含量的增加,土壤的抗风蚀强度增强,凡是有机质含量较高的土地利用类型,其土壤的抗风蚀强度较强,例如：人造林地的土壤有机质含量为3.904%,其土壤风蚀相对强弱指数是1.726;未成林林地的土壤有机质含量为2.775%,其土壤风蚀相对强弱指数是23.409;人造林地的土壤有机质含量高于未成林林地,而人造林地的土壤风蚀相对强弱指数小于未成林林地,也就是人造林地的抗风蚀强度大于未成林林地。因此,应当针对阴山北麓处于西北风主风向地带、风速大、土壤风蚀易发生的实际情况,合理保护和利用有限的土地资源,使土壤资源得以保护。     

农田和果园土壤有机碳氧化稳定性和储量差异

不同土地利用方式下有机碳的含量和性质变化越来越受到人们的关注。以黄土高原南部高原沟壑区(长武地区)塬面上农田以及不同树龄的果园为对象,研究了土壤总有机碳、易氧化有机碳和难氧化有机碳含量,比较了不同利用方式下土壤有机碳的氧化稳定系数(Kos)和有机碳密度差异。结果显示,该区域果园表层土壤总有机碳的整体水平与农田相当,但果园总有机碳、易氧化有机碳随果园年限增长有降低的趋势。在土壤剖面中,总有机碳、易氧化有机碳及难氧化有机碳都随深度下降而下降的趋势;而Kos值随剖面深度和果园年限增长而呈升高的趋势。0～2 m土壤剖面有机碳储量从高到底顺序是:农田>新果园(小于5年果园)>盛果期果园(10～15年果园)>老果园(15年以上果园)。以农田为基准,在0～200 cm厚度土层中,新果园有机碳储量下降了6.1%,盛果期果园下降了9.3%,老果园有机碳储量下降了22.4%。说明随着果园年限的增长,土壤有机碳储量降低。     

草地退化对青海湖流域小蒿草草甸土壤碳密度的影响

以青海湖流域小嵩草草甸土壤为研究对象,对不同退化程度下小蒿草草甸土壤容重和有机碳含量进行了测定,并在此基础上确定了土壤有机碳密度。结果表明:随着小嵩草草甸退化程度的加剧,其土壤容重在剖面上表现为逐渐增大趋势,土壤有机碳含量从表面逐渐减小,特别是0—10 cm表层有机碳含量减少尤为明显,未退化的表层有机碳平均含量是严重退化的6.5倍。土壤有机碳密度变化与有机碳含量在4种不同退化植被土壤中表现一致;4种不同退化程度小嵩草草甸0—100 cm土壤有机碳密度分别为（10.74±3.03）,（12.41±4.15）,（8.04±6.24） kgC/m²和（4.56±0.70） kg/m²,即轻度退化 > 未退化 > 中度退化 > 重度退化,说明随退化程度的加剧,土壤有机碳密度呈现显著下降趋势,但轻度退化有助于碳积累。     

Managing crop residues for the retention of carbon

Soil organic matter, a major sink for carbon, is controlled by many factors that have complex interactions. The management of crop residues is of primary importance. Reduced tillage and no-tillage practices result in a significant build-up of soil organic matter because they greatly reduce the rates of decomposition of both the native soil organic matter and of the crop residues. The crop residues decompose slower because most remain on the soil surface where there is less biological activity, and the native soil organic matter decomposes slower because there is less tillage for aerating the soil and for breaking the aggregates that expose organic compounds to the soil microorganisms. Crop residues, however, are highly variable. Although most crop residues contain about 40 percent carbon, the nitrogen contents range from very low to more than 3.5 percent. For carbon to be stabilized in the soil as organic matter, there must be adequate nitrogen available in the system and this factor is frequently overlooked. Climate is often the most critical factor determining the sustainability and enhancement of soil organic matter. As temperatures increase, organic matter decomposition, particularly in frequently tilled soils, is greatly accelerated. As precipitation decreases, there is less biomass produced for replenishing decomposed carbon. Consequently, soil organic matter maintenance becomes increasingly difficult in either hot or arid regions, and particularly difficult in areas that are both hot and arid. Semiarid regions comprise almost 40% of the world's land area so management of crop residues in these fragile areas is important in relation to the global C picture.     

利用离体umu/SOS测试与活体蚯蚓彗星试验评价再生水灌溉土壤的遗传毒性

污水和再生水灌溉在我国北方地区十分普遍,由于长期灌溉导致土壤中遗传毒性物质累积并因此而引发的生态安全问题值得研究。本研究利用离体umu/SOS测试与活体蚯蚓彗星试验评价北京市郊区再生水灌溉土壤中遗传毒性物质的积累。umu/SOS测试得到表征样品遗传毒性大小的β-半乳糖苷酶诱导活性（IU值）,以达到阳性时（诱导比率R=2）需要的土壤重量（G）来反映土壤样品的相对遗传毒性。活体蚯蚓彗星试验中,以尾矩（TM）表征土壤遗传毒性的大小。研究结果表明,再生水灌溉使得土壤的遗传毒性增大,随着再生水灌溉量的增加,土壤的G值减小,TM值增大,G值与TM值之间呈现明显相关关系,说明主要遗传毒性物质是有机污染物。离体umu/SOS测试和活体蚯蚓彗星试验的联合应用,可以快速有效地筛选出遗传毒性高风险土壤样品。     

有机农业施肥方式对土壤微生物活性的影响研究

综述了国内外有机农业施肥方式对培肥土壤及土壤主要微生物活性的影响，有机农业施肥方式显著增加土壤微生物数量，调控微生物种群结构，提高土壤有益微生物种群数量，土壤微生物量C、N含量倍数增加。阐明施用有机肥料对维持土壤微生物多样性与生态稳定性的必要性，并展望了施用有机肥与土壤微生物活性的关系。     

Effect of organic matter on the biodegradation of some organochlorine insecticides in submerged soils

The effect of organic matter in the biodegradation of the organochlorine insecticides DDT, endrin, heptachlor, and the four isomers of BHC (α, β, γ, and δ) was studied In two soils under submerged soil condition. The four insecticides were found to degrade biologically at a faster rate in non-sterilized than in sterilized soil. Adding organic matter to the soil seems to increase its organic chemical adsorption of insecticides slightly, but not significantly when compared to initial adsorption in the control soil. When the soil has a relatively high content of organic matter, addition of more organic matter seems to have no effect. When the soil has little organic matter, however, a more pronounced effect is obtained.     

Impact of tillage intensity on clay loam soil structure

Soil structure and structural stability are key parameters in sustainable soil management and optimum cropping practices. This study aimed to improve the knowledge of potential precision tillage practices by characterizing the effect of varied tillage intensities on structural properties of a clay loam soil. An experiment with seedbed preparation was conducted using a power take‐off‐driven rotovator equipped to measure torque and angular velocity and with operational speed (OS) and rotational speed (RS) as main factors. Effects of soil coverage prior to tillage and wheeling directly after tillage were measured at one combination of OS and RS. The soil was sampled at 0–80 mm depth. Under slow OS (2.9 km hr^?1) compared with fast OS (6.3 km hr^?1), specific energy input was greater (116 and 52 J kg^?1 on average, respectively), and it increased with RS. Wheeling resulted in larger aggregate diameter right after tillage (at T1; 56 mm as geometric mean compared with 9 mm), with 42 times smaller geometric mean of air permeability 45 days after tillage (at T2) and with greater soil dispersibility at T2. Highly significant correlations were observed between soil dispersibility and energy input, specific surface area of aggregates, fractions of small (<4 mm) and medium (8–16 mm) aggregates, and geometric mean diameter. Slow OS combined with fast RS showed significantly greater air permeability than all other treatments. The results suggest that there is a potential for controlling soil structure in seedbed preparation by minimizing compaction from traffic and adapting site‐specific control of rotovation intensity.