Influence of catclaw Mimosa monancistra on the dissipation of soil PAHs

Phytoremediation is a cost-effective biotechnology for decontamination of polycyclic aromatic hydrocarbons (PAHs)-polluted soils. A greenhouse experiment was conducted to determine the growth of Mimosa monancistra, a N2-fixing leguminous plants, and its capacity to remove phenanthrene, anthracene, and benzo(a)pyrene (BaP)from soil. The PAHs decreased shoot and root dry biomass of M. monancistra 2.7- and 3.9-fold, respectively, compared to uncontaminated soil and inhibited nodule formation. The removal of phenanthrene and anthracene was similar in vegetated and unvegetated soil, but the dissipation of BaP was significantly faster in vegetated soil as compared to unvegetated soil after 14, 56, 70, and 90 d. After 90 d, dissipation of BaP was 96% in vegetated soil and 87% in unvegetated soil. Nitrification and ammonification were not affected by the addition of PAHs as concentrations of NH4+, NO2-, and NO3- were similar in contaminated and uncontaminated vegetated soil. Growth of M. monancistra was inhibited by contamination with hydrocarbons, but removal of BaP was accelerated in the rhizosphere.     

Comparative absorption and tissue distribution of <Superscript>14</Superscript>C-benzo(a)pyrene and <Superscript>14</Superscript>C-phenanthrene in the polar cod (<Emphasis Type="Italic">Boreogadus saida</Emphasis>) following oral administration

The Arctic is an important sink for organic pollutants such as polycyclic aromatic hydrocarbons (PAHs) long-range transported from industrial regions. With the retreat of sea ice and increasing anthropogenic activities such as the oil and gas industries, local sources of PAHs are expected to increase both through operational and accidental discharges. There is a need to increase our knowledge concerning the uptake and distribution of organic pollutants, in particular PAHs, to evaluate the risk these toxic compounds may represent for Arctic species. The absorption and tissue distribution of ¹⁴C-benzo(a)pyrene (BaP) and ¹⁴C-phenanthrene (Phen) were studied in the polar cod (Boreogadus saida), a key Arctic species. After a single oral dose of BaP (1.15 ± 0.36 mg/kg fish) or Phen (0.40 ± 0.12 mg/kg fish), corresponding to 0.12 ± 0.03 mCi/kg fish, the tissue distribution was followed through 30 days by means of whole-body autoradiography and liquid scintillation counting of liver and bile. For both compounds, radiolabeling was mainly present in the bile and the intestines throughout the study period. Phen-derived radioactivity, however, appeared to be more systemically distributed compared to BaP. Furthermore, a far higher amount of irreversibly bound BaP-derived radioactivity was present in the intestinal mucosa compared to Phen, indicating a more extensive formation of reactive intermediates from the former compared with the latter. Liquid scintillation counting confirmed that radioactivity was present in the liver at all time points for both groups although the levels were low in the BaP group. These results strongly indicated that both compounds and/or their metabolites undergo enterohepatic circulation.     

低浓度苯并[a]芘诱导赤子爱胜蚓HSP70和HSP90转录上调研究

为寻找土壤低浓度多环芳烃污染分子生物标记物,采用了抑制消减双杂交的方法构建了赤子爱胜蚓在苯并[a]芘（BaP）人工土壤污染胁迫下的差异表达cDNA文库,经测序和基因比对分析后,在上调文库中分别发现2个与热休克蛋白HSP70和1个与HSP90显著匹配的cDNA克隆.经定量PCR验证了0。1 mg·kg^-1和1。0 mg·kg^-1 BaP对赤子爱胜蚓HSP70和HSP90的诱导作用,表明这两个新克隆到的赤子爱胜蚓热休克蛋白基因可作为土壤污染监测的备选分子生物标记物.     

温带荒漠中温度和土壤水分对土壤呼吸的影响

荒漠对气候变化具有高度敏感性, 深刻认识和量化非生物因子对荒漠生态系统土壤呼吸的影响具有重要意义。采用自动CO₂通量系统(Li-8100)监测了梭梭(Haloxylon ammodendron)、假木贼(Anabasis aphylla)和盐穗木(Halostachys caspica)群落生长季土壤呼吸及温度、土壤含水量等, 深入分析了水热因子对土壤呼吸的影响。土壤呼吸具有不对称的日格局, 最小值出现在8:00, 最大值在12:00~14:00。土壤呼吸的季节格局与气温变化基本同步, 最小值在生长季末期(10月), 最大值在生长季中期(6~7月)。梭梭、假木贼和盐穗木群落生长季平均土壤呼吸速率分别为0.76、0.52和0.46 μmol CO₂·m^-2·s^-1。气温对假木贼(51%)和盐穗木群落(65%)土壤呼吸季节变化的解释率高于梭梭(35%)。梭梭、假木贼和盐穗木群落土壤呼吸温度敏感性(Q₁₀)逐渐增大, 基础呼吸速率(R₁₀)逐渐减小。剔除温度影响后, 梭梭、假木贼群落土壤呼吸与土壤含水量呈显著的幂二次方函数关系, 盐穗木群落两者关系却明显减弱, 未达到显著水平。气温、土壤含水量的二元方程均能解释群落土壤呼吸大部分的时间变异: 梭梭群落71%~93%、假木贼群落79%~82%、盐穗木群落70%~80%。人工模拟降水后土壤呼吸速率表现出降水后10 min减小、180 min时明显增加、达到最大值后再次衰减的现象。5和2.5 mm降水处理下的土壤呼吸速率最大值和其后的递减值高于对照处理, 土壤呼吸增加、达到峰值和其后递减过程与5 cm土壤温度变化基本同步。     

有机肥对桃园土壤硝态氮分布的影响

于2004—2005年在北京市平谷区有机桃园设置不同有机肥处理：2年连续施有机肥,年均67 500 kg·hm^-2（T₁）;第一年不施肥,第二年施有机肥135 000 kg·hm^-2（T₂）;第一年不施肥,第二年施有机肥67 500 kg·hm^-2（T₃）;不施肥对照（CK）,并于2006年对0～120 cm土层土壤进行取样分析,研究施用有机肥对土壤硝态氮分布和淋失的影响.结果表明：对照土壤中硝态氮分布较均匀,T₁和T₃在0～120 cm土层硝态氮浓度变化呈单峰曲线,其中60 cm以上较高,在60～120 cm逐渐降低;而T₂土壤硝态氮浓度由浅到深逐渐增加,峰值出现在100～120 cm土层,其在60 cm以下土层的硝态氮浓度在所有处理中最高,说明过量施用有机肥易导致硝态氮的淋失.相关分析表明,土壤硝态氮的浓度和分布与多年施氮总量、最近一年施氮量和检测点与树的距离呈显著相关关系,并据此建立了有机肥施用与土壤剖面硝态氮浓度之间的相关模型.     

Comparative Sorption of Phenanthrene and Benzo[α]pyrene to Soil Humic Acids

Sorption of phenanthrene (Phen) and benzo[α]pyrene (BaP) by humic acids (HAs) extracted from four typical soils in China, including cinnamon soil, fluvo-aquic soil, red soil, and mountain meadow soil were investigated. All sorption data were fitted well by the Freundlich model, but BaP exhibited stronger and more nonlinear sorption than Phen by a given HA. For Phen isotherms, there was a positive relation between K _oc values and aliphaticity of HAs, whereas a negative correlation was observed between n values and aliphaticity. This indicated the importance of aliphatic groups in Phen sorption capacity and nonlinearity. Compared to Phen, a similar trend was obtained between n values of BaP and aliphaticity or aromatic carbon. However, no correlation existed between K _oc values for BaP and aliphaticity or aromatic carbon.     

Formation and persistence of benzo[a]pyrene-diolepoxide-DNA adducts in liver of English sole (Parophrys vetulus)

The formation of DNA adducts from the carcinogenic environmental pollutant benzo[a]pyrene (BaP) was investigated in liver of English sole (Parophrys vetulus), a fish species that exhibits a high prevalence of liver neoplasms in several polycyclic aromatic hydrocarbon (PAH)-contaminated areas of Puget Sound, WA. Analysis by the 32P-postlabeling assay of hepatic DNA digests from English sole exposed parenterally to BaP showed the presence of BaP-diol epoxide (BaPDE)-DNA adducts. When English sole were injected with 2-15 mg BaP/kg body wt., one major adduct was detected and was identified as the anti-BaPDE-DNA adduct. Moreover, in English sole sampled at 1, 28 and 60 days post-exposure to 15 mg BaP/kg body wt., there was no significant change in the level of the anti-BaPDE-DNA adduct. The autoradiographs of 32P-labeled hepatic DNA digests from fish exposed to 100 mg BaP/kg body wt. showed an elongated spot suggesting the presence of more than one adduct. Chromatography on large polyethyleneimine sheets (20 x 20 cm) showed 2 spots with the same chromatographic characteristics as those of syn- and anti-BaPDE-deoxyguanosine adduct standards. Mild acid hydrolysis of hepatic DNA of English sole, exposed to 100 mg BaP/kg body wt., also revealed the presence of tetrols derived from both anti- and syn-BaPDE, thus confirming the presence of syn- and anti-BaPDE. In fish exposed to 2-100 mg BaP/kg body wt., a linear (0.996) dose response for anti-BaPDE-DNA adduct formation was observed. The results from this study offer the first direct evidence for the formation of the suspected ultimate carcinogen, BaPDE, in liver of English sole exposed to BaP in vivo and thus further support the hypothesis that exposure to PAHs is an important factor in the etiology of hepatic neoplasms in English sole from contaminated sites.     

Threshold distances and depths of nucleopolyhedrovirus in soil for transport to cotton plants by wind and rain

Two aspects of abiotic transport of nucleopolyhedrovirus from soil to cotton plants were examined in greenhouse experiments: the distance from the plants and depth in soil from which the virus could be transported under controlled conditions of soil type and moisture, wind, and precipitation. Transport distance and depth were tested separately under relatively conducive (precipitation/sandy soil and wind/clay soil) and non-conducive (precipitation/clay soil and wind/sandy soil) conditions, as determined in previous research. The amount of virus transported by precipitation generally decreased as distance from the plant increased, but in wind the amounts of virus transported were best described by polynomial models, with transport efficiency usually peaking at a distance of 60 cm. Depending on plant height and tissue, the farthest distances that virus was transported ranged from 30 to 60 cm by precipitation from clay soil, 60-75 cm in precipitation/sand, 60-80 cm in wind/clay, and 60-80 cm in wind/sand. In the depth experiments, transport by precipitation and wind generally decreased as the depth of virus in soil increased. The greatest depth from which NPV was transported ranged from 0 to 0.5 cm by precipitation from clay soil, 0.5-1.0 cm in precipitation/sand, 1.0-2.0 cm in wind/clay, and 0.5-1.0 cm in wind/sand. All of the experimental parameters (distance or depth, soil type, plant height, plant tissue) and all two-way interactions significantly (P<0.05) affected transport in all four experiments, except for the "soilxplant tissue" interaction in the depth/wind experiment. In all of the experiments, transport was significantly greater (P<0.05) to lower than to upper portions of plants and to leaves than to buds and squares. Transport was significantly greater from sandy soil than from clay in precipitation, and it was greater from clay than from sandy soil in wind. The results will contribute to NPV epizootiology, microbial control, and risk assessment.     

三江平原碟形洼地-岛状林土壤氮磷空间分布及生态化学计量特征

为阐明由碟形洼地-岛状林方向土壤养分的空间分布特征,选取非生长季中国科学院三江平原沼泽湿地生态试验站内的碟形洼地为研究对象,探讨土壤全氮和全磷含量及其化学计量比的空间分布特征及其影响因素。结果表明:由碟形洼地-岛状林方向,全氮、全磷和氮磷比在各样点的平均值分别呈"V"字、倒"N"字和"V"字型分布,土壤全氮、全磷与氮磷比含量的平均值分别为2278.11 mg/kg、820.50 mg/kg与2.44,变异系数为全氮(51.77%)氮磷比(36.07%)全磷(13.65%)。在0—50 cm土层内,全氮、全磷和氮磷比总体呈随土壤深度增加而逐渐降低的趋势,其中全氮主要集中于不同样点土壤的中上层,各样点的最高值均分布在土壤表层区域;全磷的富集深度与全氮相同,但在土壤20 cm深度各样点含量相近,后在20—50 cm深度内呈逐渐下降趋势;氮磷比在各样点的最高值与全氮和全磷分布总体一致,富集深度与两元素呈基本一致趋势。相关性分析表明,碟形洼地-岛状林方向土壤全氮与全磷之间均呈现出良好的相关关系,其中土壤有机质的分布,植物与水文状况、季节变化和土壤温度也在养分分布中起重要作用。     

川西北草原土壤及冷暖季牧草微量元素含量比较

改善土壤的理化环境及提高牧草的营养水平必须了解草地土壤及牧草微量元素的分布与含量。试验从川西北草地的亚高山丘原草甸、亚高山平坝草甸和沼泽平坝草甸采集土样和冷暖季草样。土样采集深度范围是0～10cm,10～20cm,20～30cm。应用火焰原子吸收光谱法测定了草样中铜、铁、锰、锌和钴的含量和土样中这些元素的有效态含量,应用氟离子选择电极法测定了土样中的氟离子浓度和草样中的氟含量。土壤pH高低顺序为草甸土>冲积土>泥炭草甸土,pH随土壤深度变深而下降;土壤和牧草的钴含量都处于缺乏状态,分别为0.64mg/kg和0.26mg/kg。牧草铁和锰含量都高于正常水平,铁为414.51～565.06mg/kg,锰为138.68～247.09mg/kg.     

洞庭湖湿地土壤碳、氮、磷及其与土壤物理性状的关系

以洞庭湖3类典型湿地的8个土壤剖面为代表,研究了土壤碳、氮、磷,微生物量碳、氮、磷和土壤物理性状的分布特征.结果表明,土壤表层有机碳含量为19.63～50.20 g·kg^-1,微生物量碳为424.63～1 597.36 mg·kg^-1,微生物量碳占有机碳的比例为3.17%～4.82%;土壤表层全氮1.85～4.45 g·kg^-1,微生物量氮5.90～259.47 mg·kg^-1,微生物量氮占全氮的比例3.13%～6.42%;土壤表层微生物量磷含量顺序为:湖草洲滩地(200.99 mg·kg^-1)＞垦殖水田(163.27 mg·kg^-1)＞芦苇洲滩地(24.16 mg·kg^-1),微生物量磷占全磷的比例为1.09%～11.20%;土壤表层容重0.65～1.04 g·cm^-3;土壤表层粘粒(＜0.001mm)26.24%～39.48%.土壤表层有机碳、全氮、微生物量氮、微生物量磷的含量,湖草洲滩地＞垦殖水田＞芦苇洲滩地.土壤表层微生物量碳,垦殖水田和湖草洲滩地接近,而大于芦苇湿地;土壤表层容重,芦苇洲滩地＞垦殖水田＞湖草洲滩地;土壤表层＜0.01 mm、＜0.001 mm粘粒,湖草洲滩地、芦苇洲滩地＞垦殖水田.湿地土壤剖面中有机碳、微生物量碳、全氮、微生物量氮、微生物量磷、容重以及微生物量碳占有机碳的比例、微生物量氮占全氮的比例、微生物量磷占全磷的比例均随深度的增加而降低,至一定深度稳定,而土壤全磷在剖面上下的差异很小.湿地土壤微生物量碳、氮、磷之间呈极显著的正相关关系;土壤容重与有机碳、全氮、微生物量碳、氮、磷之间呈极显著指数负相关关系.湿地土壤＜0.001 mm粘粒与有机碳、全氮、微生物量碳、氮、磷含量呈极显著对数正相关关系.     

疏勒河源高寒草甸土壤微生物生物量碳氮变化特征

土壤微生物生物量是土壤有机质的活性部分,是反映土壤质量和碳氮循环机制的重要指标。本文以青藏高原东北缘疏勒河源高寒草甸为研究对象,对土壤微生物生物量碳（SMBC, mg/kg）和微生物生物量氮（SMBN, mg/kg）的不同季节（春、夏、秋、冬）和土层（0—10、10—20、20—30、30—40、40—50 cm）变化特征及其影响因素进行研究。结果表明：（1）不同土层SMBC均表现为春季开始逐渐升高、夏季达到最大值、秋季逐渐降低、冬季值最小,而SMBN春季开始逐渐降低、夏季值最小、秋季逐渐升高、冬季达到最大值。（2）SMBC、SMBN随着土壤深度的增加而下降,0—10 cm层SMBC、SMBN显著高于40—50 cm层,且SMBC、SMBN0—10 cm层的季节变幅显著大于40—50 cm层。（3）0—50 cm土层SMBC/SMBN表现为春季开始逐渐升高、夏季达到最大值、秋季逐渐降低、冬季值最小,其季节变化范围为8.77—23.59,处于较高水平。（4）SMBC、SMBN、SMBC/SMBN的季节和土层变化主要受植被地下生物量和土壤温度的影响。（5）各土层SMBC/SOC均表现为春季开始逐渐升高、夏季达到最大值、秋季逐渐降低、冬季值最小,而SMBN/TN春季开始逐渐降低、夏季值最小、秋季逐渐升高、冬季达到最大值。除夏季土层间无显著差异外,SMBC/SOC与SMBN/TN均表现为0—10 cm层显著高于40—50 cm层。（6）0—50 cm土层SMBC/SOC夏秋季显著高于冬春季且其季节变化范围为0.58%—1.18%,而SMBN/TN秋冬季显著高于夏季且其季节变化范围为0.39%—0.72%。综上,季节变化和剖面深度均对SMBC、SMBN产生显著影响且0—10 cm土层对SMBC、SMBN的累积能力最强。     

Estimation of Toxicity Equivalency and Probabilistic Health Risk on Lifetime Daily Intake of Polycyclic Aromatic Hydrocarbons from Urban Residential Soils

In this study, toxicity equivalents and health risks, based on concentration of 16 priority polycyclic aromatic hydrocarbons (PAHs) in urban residential soils were estimated for the human population in Gwalior, India. Benzo(a)pyrene total potency equivalents (BaP TPE) were estimated for assessment of human health risk from direct contact with PAH-contaminated soil. Potential risk to contaminated groundwater from leaching of carcinogenic PAHs was assessed by estimating the index of additive cancer risk (IACR). On the basis of lifetime average daily intake of 16 PAHs through ingestion of PAH-contaminated soils, lifetime cancer risk to human adults and children was estimated. The concentration of probable human carcinogenic PAHs in soils accounted for 38% of ∑16PAHs. BaP TPE and index of additive cancer risk (IACR) were lower than guideline values of 0.6 mg kg^?1 and <1, respectively. Estimated lifetime average daily intakes of PAHs via soil ingestion were lower than recommended dose. However, the ILCR for human adults was within acceptable limits recommended by regulatory agencies, but may need action for children in Gwalior, India.     

水氮配合对绿洲沙地农田玉米产量、土壤硝态氮和氮平衡的影响

在黑河中游边缘绿洲沙地农田研究了不同的水氮配合对玉米产量、土壤硝态氮在剖面中的累积和氮平衡的影响.结果表明,施氮处理较不施氮处理产量增加48.22%～108.6%,施氮量超过225 kg hm-2,玉米产量不再显著增加.受土壤结构影响土壤硝态氮在土壤中呈"W"型分布,即土壤硝态氮含量在0～20 cm、140～160 cm和260～300 cm土层均出现峰值,并随施氮量增加,峰值增高.在常规高灌溉量处理硝态氮含量峰值最高值出现在260～300 cm土层,节水25%灌溉处理硝态氮含量峰值最高值出现在土壤表层0～20 cm土层.在常规高灌溉量处理0～300 cm土层中200～300土层硝态氮累积量所占比例最高,介于27.56%～51.86%之间;节水25%灌溉处理在0～300 cm土层中100～200土层硝态氮累积量所占比例最高,介于32.94%～38.07%之间;表明低灌溉处理下土壤硝态氮在土壤浅层累积较多,而高灌溉处理使更多的硝态氮淋溶至土壤深层.与2006年相比,2007年不施氮处理0～200 cm土层土壤硝态氮含量和积累量均明显减少;而施氮处理变化很小,在低灌溉处理甚至表现出硝态氮含量和积累量增加,表明施氮是土壤硝态氮累积的主要来源,而灌溉则使硝态氮向土壤深层淋溶.0～200 cm 土层土壤硝态氮累积量平均介于27.66～116.68 kg hm-2、氮素表观损失量平均介于77.35～260.96 kg hm-2,和施氮量均呈线性相关,即随施氮量增加,土壤硝态氮累积量和氮素表观损失量均增加,相关系数R2介于0.79～0.99之间,相关均显著.随施氮量增加,玉米总吸氮量和氮收获指数增加,氮的农学利用率降低,而灌溉的影响较小.施氮量超过225 kg hm-2时,地上部植株氮肥吸收利用率和籽粒氮肥吸收利用率开始有降低趋势.所以,在沙地农田,节水10%～25%的灌溉水平和225 kg hm-2的施氮水平可以在避免水肥过量投入的基础上减少土壤有机氮淋溶对地下水造成的污染威胁.     

Levels,Sources, and Toxic Potential of Polycyclic Aromatic Hydrocarbons in Urban Soil of Delhi,India

This study was done to determine the concentration of PAHs in urban soil of Delhi (India). Surface top soil (up to 10 cm depth) samples were collected from four different sampling sites including industrial, roadside, residential, and agricultural areas of Delhi and 16 USEPA priority polycyclic aromatic hydrocarbons (PAHs) were evaluated. Total PAH concentrations at industrial, roadside, residential, and agricultural sites were 11.46 ± 8.39, 6.96 ± 4.82, 2.12 ± 1.12, and 1.55 ± 1.07 mg/kg (dry weight), respectively, with 3–7 times greater concentrations in industrial and roadside soils than that in residential and agricultural soils. The PAH pattern was dominated by 4- and 5-ring PAHs (contributing >50% to the total PAHs) at industrial and roadside sites with greater concentration of fluoranthene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]anthracene, benzo[ghi]perylene, and pyrene, whereas, residential and agricultural sites showed a predominance of low molecular weight 2- and 3-ring PAHs (fluoranthene, acenaphthene, naphthalene, chrysene, and anthracene). Isomeric pair ratios suggested biomass combustion and fossil fuel emissions as the main sources of PAHs. The toxic equivalency factors (TEFs) showed that carcinogenic potency (benzo[a]pyrene-equivalent concentration (B[a]P_eq) of PAH load in industrial and roadside soils was ～10 and ～6 times greater than the agricultural soil.     

Biodegradation of [(sup14)C]Benzo[a]pyrene Added in Crude Oil to Uncontaminated Soil

To investigate the possible cometabolic biodegradation of benzo[a]pyrene (BaP), crude oil spiked with [7-(sup14)C]BaP and unlabeled BaP was added to soil with no known pollution history, to give 34 g of oil and 67 mg of BaP/kg of dry soil. The oil-soil mixture was amended with mineral nutrients and incubated in an airtight container with continuous forced aeration. Total CO(inf2) and (sup14)CO(inf2) in the off-gas were trapped and quantified. Soil samples were Soxhlet extracted with dichloromethane at seven time points during the 150-day incubation period, and the extracted soil was subjected to further fractionation in order to recover reversibly and irreversibly bound radiocarbon. Radiocarbon recovery was 100% (plusmn) 3% for each time point. During the first 50 days of incubation, no (sup14)CO(inf2) was evolved, but over the next 100 days, 50% of the BaP radiocarbon was evolved as (sup14)CO(inf2). At 150 days, only 5% of the intact BaP and 23% of the crude oil remained. Of the remaining radiolabel, 20% was found in solvent-extractable metabolites and 25% was incorporated into soil organic matter. Only 1/10 of this could be solubilized by chemical hydrolysis. An abiotic control experiment exhibited binding of only 2% of the BaP, indicating the microbial nature of the BaP transformations. We report that in soil containing suitable cosubstrates, BaP can be completely degraded.     

宁夏引黄灌区秸秆还田对麦田土壤硝态氮淋失的影响

以宁夏引黄灌区为例,探索秸秆还田条件下冬小麦土壤硝态氮淋失规律。试验设置常规施肥(CK)、常规施肥条件下施用4500kg/hm2(T1,半量还田)和9000 kg/hm2(T2,全量还田)秸秆3个处理。利用树脂芯法吸附10、20、30、60cm和90cm土层的硝态氮流失量。结果表明:硝态氮(纯N)淋失量6.26—12.85 kg/hm2,是冬小麦施用化肥氮量的2.78%—5.71%。与对照CK相比,T1和T2在10cm土层减少0.09%和3.97%;20cm土层减少8.51%和9.81%;30cm土层减少2.25%和10.34%;60cm土层减少23.85%和13.08%;90cm土层减少27.65%和20.73%。10cm和20cm土层,处理与对照以及处理之间均未到显著性差异(P0.05);30cm处理,T1与CK以及T1与T2未达到显著性差异,但T2与CK达到显著性差异表明全量还田效果最好;60cm土层,处理与对照、以及处理之间均达到显著性差异;90cm土层,处理与对照之间达到显著性差异,处理之间未达到显著性差异。硝态氮淋失主要发生在冬小麦返青至灌浆期间,占全生育期淋失量的52.95%—67.79%。T1、T2冬小麦产量增产率分别为10.11%与11.51%。可见,稻秆还田能够减少灌区土壤硝态氮淋失量。     

灌溉方法与施氮对土壤水分、硝态氮和小麦生长发育的调控效应

为探明玉米秸秆还田下小麦的合理灌溉与施肥方法,于田间研究了漫灌(FI)、微喷灌(SI)、滴灌(DI)和灌水施氮模式(N₁, 基施纯N 157.5 kg·hm^-2+拔节期施纯N 67.5 kg·hm^-2; N₂, 基施纯N 157.5 kg·hm^-2+拔节期施纯N 45.0 kg·hm^-2+灌浆期施N 22.5 kg·hm^-2)对土壤水分、硝态氮(NO₃^--N)含量和小麦生长发育的影响.结果表明: 灌溉方法和灌水施氮模式共同影响土壤含水量和贮水量的变化.其中,灌溉方法对越冬期和返青期0～60 cm、孕穗期和灌浆期0～160 cm、成熟期100～160 cm土层含水量影响相对较小,对越冬期和返青期80～160 cm、成熟期0～80 cm土层含水量影响大;FI对含水量和贮水量影响最大,DI次之,SI最小;SI和DI的灌水施氮模式中灌水量多,则土层含水量高、贮水量多,变化大.NO₃^--N含量受灌溉方法和施氮的影响,施氮对0～20 cm土层影响大,SI生育期NO₃^--N含量变化大,DI越冬期至孕穗期NO₃^--N含量变化小,此后变化大,FI与DI相反;生育前中期灌水量对NO₃^--N含量影响大,后期施氮对NO₃^--N含量影响大;SI和DI的2种灌水施氮模式中冬前灌水量多的NO₃^--N含量变化大.灌溉方法中SI越冬期总茎数和单株分蘖高,成穗率高,成穗数多,产量、水分利用效率(WUE)和氮素利用效率最高,滴灌次之,漫灌最低;SI和DI中N₁生育期总茎数、成穗数多,但穗粒数和千粒重低,产量、WUE和氮素利用效率低于N₂.因此,玉米秸秆还田后播种小麦,微喷灌代替漫灌生育期灌4水,施足基肥,拔节期和灌浆期分次追氮,是山西南部小麦-玉米一年两熟区小麦节水高产高效栽培模式.     

施钾量和施钾时期对小麦氮素和钾素吸收利用的影响

利用¹⁵N示踪技术,研究了施钾量和施钾时期对高产小麦氮素和钾素吸收利用的影响.结果表明： 0～20 cm土层土壤速效钾含量为118.5 mg·kg^-1时,一次性基施钾肥未提高植株的氮、钾积累量;速效钾含量为79.0 mg·kg^-1时,施钾显著提高了植株的氮、钾积累量.采用分期施钾时（1/2基施、1/2拔节期追施）,随施钾量增加,小麦吸收的肥料氮和土壤氮量及追施氮肥在土壤中的残留量均增加,肥料氮的损失量降低.分期施钾显著提高了植株的氮、钾积累量、吸收效率和生产效率,当施钾量为135 kg·hm^-2时,与一次性施钾相比,分期施钾促进了植株对追肥氮和土壤氮的吸收,提高了追施氮肥在土壤中的残留量.结果还表明：施钾提高了小麦的籽粒产量、蛋白质含量和湿面筋含量;分期施钾处理优于一次性施钾处理,以K45+45（45 kg·hm^-2基施、45 kg·hm^-2拔节期追施）处理最优.过多施钾使小麦产量和品质趋于降低.     

中国马尾松林土壤肥力特征

土壤肥力是各因素的综合作用和反映，也是林地生产力的基础。为了解马尾松分布区林下土壤肥力状况，利用499条文献数据、134条历史调查数据和131条当前调查数据中0-20 cm和20-40 cm土层的pH值、有机质、全氮、全磷、全钾、碱解氮、有效磷和速效钾，根据全国第二次土壤普查养分分级标准和内梅罗指数法分别对土壤养分单一指标丰瘠水平和综合肥力状况进行评估，并分析马尾松天然林与人工林和纯林与混交林间土壤肥力特征的差异，为马尾松林可持续经营和生产力提高提供科学依据。结果表明：（1）0-20 cm和20-40 cm土层土壤pH值、有机质、全氮、全磷、全钾、碱解氮、有效磷、速效钾的平均值分别为4.79和4.91、33.78 g/kg和19.92 g/kg、1.82 g/kg和1.32 g/kg、0.46 g/kg和0.40 g/kg、14.49 g/kg和15.71 g/kg、88.00 mg/kg和59.41 mg/kg、4.94 mg/kg和2.38 mg/kg、71.72 mg/kg和52.99 mg/kg；（2）除土壤有机质、全氮和全钾含量外，两个土层其他土壤养分指标的丰瘠水平在"较缺"水平及其以下；（3）0-20 cm土层土壤肥力指数（0.97）大于20-40 cm土层（0.77），土壤有效磷含量的肥力指数均最小（0.60和0.33）；（4）除20-40 cm土层pH值、碱解氮和速效钾含量外，其他土壤养分指标和肥力指数均表现为混交林>纯林；这些指标在天然林与人工林间的差异因指标而异。总体来看，马尾松林土壤磷和钾养分的供给潜力和能力较弱，土壤综合肥力状况也偏"贫瘠"，其中土壤有效磷含量最低，肥力指数也最小；0-20 cm土层的土壤肥力状况优于20-40 cm土层，均受林分起源（天然林与人工林）和林分结构（纯林与混交林）的影响；但由于指标缺乏（如物理指标）和数据分布不均衡（天然林和混交林少），土壤肥力的估算以及林分特征对土壤养分和肥力的影响还有待于进一步研究。