一株敌敌畏降解菌DDV-1(Ochrobactrium sp.)的分离鉴定及其降解特性的研究

Soil organic carbon （C） and total nitrogen （N） pools of a Chinese fir （Cunninghamia lanceolata （Lamb.） Hook.） （CF） forest, and an evergreen broadleaf （EB） forest located in mid-subtropical, southeastern China, were compared before clearcutting, with the effect of slash burning on organic C and total N in the top 10 cm of soil before and after burning also being evaluated. Prior to clearcutting CF forest had significantly lower （P 〈0.05） organic C and total N in the soil （0-100 cm） compared to EB forest with approximately 60% of the C and N at the two forest sites stored at the 0 to 40 cm soil. In post-burn samples of the 0-10 cm depth at 5 days, 1 year, and 5 years for CF and EB forests, significantly lower levels （P 〈0.05） of organic C and total N than those in the pre-burn samples were observed. Compared to the pre-burn levels, at post-burn year 5, surface soil organic C storage was only 85% in CF forest and 72% in EB forest, while total N storage was 77% for CF forest and 73% for EB forest. Slash burning caused marked long-term changes in surface soil C and N in the two forest types.     

中亚热带杉木林和常绿阔叶林土壤C、N库及其火烧后的变化

Soil organic carbon (C) and total nitrogen (N) pools of a Chinese fir (Cunninghamia lanceolate, (Lamb.) Hook.) (CF) forest, and an evergreen broadleaf (EB) forest located in mid-subtropical, southeastern China, were compared before clearcutting, with the effect of slash burning on organic C and total N in the top 10 cm of soil before and after burning also being evaluated. Prior to clearcutting CF forest had significantly lower (P < 0.05) organic C and total N in the soil (0-100 cm) compared to EB forest with approximately 60% of the C and N at the two forest sites stored at the 0 to 40 cm soil. In post-burn samples of the 0-10 cm depth at 5 days, 1 year, and 5 years for CF and EB forests, significantly lower levels (P < 0.05) of organic C and total N than those in the pre-burn samples were observed. Compared to the pre-burn levels, at post-burn year 5, surface soil organic C storage was only 85% in CF forest and 72% in EB forest, while total N storage was 77% for CF forest and 73% for EB forest. Slash burning caused marked long-term changes in surface soil C and N in the two forest types.     

灌区马铃薯-大白菜双季栽培降低土壤硝酸盐淋洗风险并增加资源利用效率的研究

To reduce the nitrate leaching risk after potato (Solanum tuberosum L.) harvest and improve nitrogen fertilizer-use efficiency, a potato-cabbage double cropping system (DCS) was established at Hetao, North China, an arid area with irrigated land. A two-year field experiment demonstrated that planting early-maturing potato cultivar under plastic mulch shortened its growth period by 14 d and allowed a second crop of cabbage to scavenge the soil residual NO 3 -N to a depth of 160 cm, substantially reducing the risk of nitrate leaching into groundwater. The yearly total N uptake in DCS was about 110 kg ha 1 more than that in the conventional cropping system (CCS), i.e., mono potato planting. This accounted for apparent nitrogen recovery (ANR) improvement of 16.90%- 26.57% in the DCS as compared to that in the CCS for both years. As a result, the soil residual NO 3 -N in the 0-160 cm soil profile in the DCS was lower than that in the CCS. The solar energy-use efficiency and soil-use efficiency were also substantially increased with DCS.     

地中海农业生态系统中土壤自生线虫种群多样性及动态研究

To determine the effect of agricultural management on the dynamics and functional diversity of soil nematode communities in a carrot field at Kibbutz Ramat Hakovesh, Israel, soil samples from 0--10 cm and 10--20 cm depths were collected during the growing season of carrot. Indices were used to compare and assess the response of soil free-living nematode communities to agricultural management. Eighteen nematode families and 20 genera were observed during the growing period, with Cephalobus, Rhabditidae, Aphelenchus, Tylenchus, and Dorylaimus being the dominant genera/families. During the planting, mid-season and post-harvest periods the total number of nematodes at both depths was significantly lower (P < 0.01) in the carrot treatment than in the control plots, while during the harvest period at both depths total nematodes and bacterivores were significantly higher in the treatment plots (P < 0.01). The values of the maturity index (MI) at both depths were found to be significantly lower in the treatment plots than in the control plots during the pre-planting period (P < 0.05). Overall, WI, MI and PPI were found to be more sensitive indicators than other ecological indices for assessing the response of nematode communities to agricultural management in a Mediterranean agroecosystem.     

温室集约化生产系统对土壤质量的影响

Composite top- and subsoil samples were collected from the greenhouses in the Al-Balawneh area,Jordan,where intensive greenhouse production system（IGPS） has been practiced since 1998,to study the impact of IGPS on soil quality as measured by the chemical and biological properties to develop a sustainable production system.The study showed that IGPS led to higher electrical conductivity in top- and subsoils compared to an uncultivated soil（control）.Quality and amount of irrigation water,lack of efficient drainage,and quantity and types of applied fertilizers were major factors resulting in salt buildup.IGPS resulted in lower total N（TN） and NO₃-N in the soil compared to the control.The lower TN was due to crop uptake,microbial immobilization,volatilization,and irregular application of composted animal manure or poultry manure.In contrast,higher residual Olsen-P content was detected in both soil layers of greenhouses than in the control.Residual P was classified as very high in the topsoil layers and sufficient to high in the subsoil layers.Residual available K in the soils of greenhouses was relatively lower than that in the control and it was,however,classified as high to very high.A large increase of Cl and a considerable decrease in the bacterial count were observed in both soil layers of IGPS compared to the control treatment.Economically sustainable soil management practices need to be adopted by farmers to achieve a sustainable and profitable production.This can be accomplished through education,targeted towards the farming community in the central Jordan Valley.     

除草剂莠去津和灭草松单用和混用在土壤中的降解

The application of a mixture of bentazone （3-isopropyl-1H-2,1,3-benzothiadiazin-4（3H）-one-2,2-dioxide） and atrazine （6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine） is a practical approach to enhance the herbicidal effect. Laboratory incubation experiments were performed to study the degradation of bentazone and atrazine applied in combination and individually in maize rhizosphere and non-rhizosphere soils. After a lag phase, the degradation of each individual herbicide in the non-autoclaved soil could be adequately described using a first-order kinetic equation. During a 30-d incubation, in the autoclaved rhizosphere soil, bentazone and atrazine did not noticeably degrade, but in the non-autoclaved soil, they rapidly degraded in both non-rhizosphere and rhizosphere soils with half-lives of 19.9 and 20.2 d for bentazone and 29.1 and 25.7 d for atrazine, respectively. The rhizosphere effect significantly enhanced the degradation of atrazine, but had no significant effect on bentazone. These results indicated that biological degradation accounted for the degradation of both herbicides in the soil. When compared with the degradation of the herbicide applied alone, the degradation rates of the herbicides applied in combination in the soils were lower and the lag phase increased. With the addition of a surfactant, Tween-20, a reduced lag phase of degradation was observed for both herbicides applied in combination. The degradation rate of bentazone accelerated, whereas that of atrazine remained nearly unchanged. Thus, when these two herbicides were used simultaneously, their persistence in the soil was generally prolonged, and the environmental contamination potential increased.     

华北平原土壤质量与农业生产的关系

Sustainable agricultural production is of vital importance to food supply security. This study aimed to investigate crop yield response to spatial variability of soil quality at a county scale in the North China Plain(NCP) and subsequently derive key soil quality indicators. Soil samples were geo-referenced and taken in 2008 from both surface(0–20 cm) and subsurface(20–40 cm) layers in132 fields throughout the Fengqiu County, located in the centre of the NCP, for subsequent soil properties' analyses. Annual crop yields were obtained from the same fields where soil samples were collected. Soil quality was evaluated based on a fuzzy set with 13 soil properties, and its spatial distributions were investigated by integrating geostatistical analysis and geographic information system(GIS) techniques. Soil quality indices were classified into five grades, and their spatial distributions were mapped within the county.The surface soil qualities were about one to two grades higher than the subsurface soil. The quality indices for surface and subsurface soils were positively associated with the annual crop yields, suggesting the importance of both. Soil organic matter, total nitrogen,available P, and available K contributed 50% of the combined weight to the soil quality index and were identified as key indicators of soil quality status in the area in terms of sustainability.     

栽培对黑土线虫营养群体的空间分布的影响

Geostatistics combined with GIS was applied to assess the spatial distribution of nematode trophic groups following two contrasting soil uses in the black soil region of Northeast China.Two plots,one with fallow for 12 years and the other cultivated,were marked on regular square grids with 2-m spacing.Soil samples were collected from each sampling point,nematodes were extracted from these samples and classified into four trophic groups:bacterivores,fungivores,plant parasites,and omnivores/predators.The numbers of total nematodes and trophic groups analyzed had normal distributions on both fallow and cultivated plots.The absolute abundances of total nematodes and trophic groups were observed to be much nore homogeneous on cultivated plot than on fallow one.Geostatistical analysis showed that the densities of total nematodes and trophic groups on both fallow and cultivated plots exhibited spatial dekpendence at the sampled scale and their experimental semivariograms were adjusted to a spherical or exponential model,except those of bacterivores and fungivores oncultivated plot.The spatial distribution of nematode trophic groups was found to be different for the two land uses,indicating that cultivation changed the native condition for soil nematode activities.     

一种测定土壤水分迁移率的方法研究

A new laboratory method was proposed to establish an easily performed standard for the determination of mobile soil water close to real conditions during the infiltration and redistribution of water in a soil. It consisted of applying a water volume with a tracer ion on top of an undisturbed ring sample on a pressure plate under a known suction or pressure head. Afterwards, soil water mobility was determined by analyzing the tracer-ion concentration in the soil sample. Soil water mobility showed to be a function of the applied water volume. No relation between soil water mobility and applied pressure head could be established with data from the present cxperiment. A simple one- or two-parameter equation can be fitted to the experimental data to parameterize soil water mobility as a function of applied solute volume. Sandy soils showed higher mobility than loamy＂ soils at low values of applied solute volumes, and both sandy and loamy soils showed an almost complete mobility at high applied solute volumes.     

水稻对水稻土中甲磺隆结合残留的响应

Metsulfuron-methyl is one of the widely used sulfonylurea herbicides. However, approximately half of the applied metsulfuron-methyl may remain as bound residues in soil. To characterize the response of rice plants to residual metsulfuron-methyl in soil, the activities of acetolactate synthase （ALS）, superoxide dismutase （SOD）, peroxidase （POD）, and catalase （CAT） were investigated in two rice varieties that differed in susceptibility to the herbicide. Changes in the activity of these enzymes in leaves and roots of Xiushui 63, a sensitive rice variety, were greater than those in a resistant variety Zhenong 952. Irrespective of variety, changes in the enzyme activity were greater in the roots than in the leaves. The activities of ALS and CAT decreased, while the SOD activity increased with the increase in the amounts of bound residues of metsulfuron-methyl （BRM） in soil. The POD activity increased at the BRM level of 0.025 mg kg^-1, but decreased at the BRM level of 0.05 mg kg^-1. The results showed that the bound residues of sulfonylurea herbicides may affect metabolism of rice plants.     

Comparison of the persistence of atrazine and metolachlor under field and laboratory conditions

A study was carried out in a loamy soil to evaluate the degradation of atrazine and metolachlor under laboratory-controlled and field-variable conditions as a function of temperature and soil moisture content. In laboratory trials, metolachlor showed fast degradation, with half-lives from 100 to 5.7 days in a temperature range from 5 to 35 degrees C at 100% of field capacity, whereas in the same conditions the degradation rate of atrazine was relatively slow, with half-lives from 407 to 23 days. Modeling of laboratory degradation data to predict field persistence was carried out. Field persistence of atrazine and metolachlor was measured in the same soil during the corn growing seasons in 1993, 1994, and 1996. In the three years the mean half-dissipation times for atrazine and metolachlor were 36 and 21 days, respectively. Calculations from model equations gave acceptable prediction of field dissipation of both herbicides. Limitations and perspectives of employed modelization procedure are discussed.     

Atrazine and metolachlor in surface runoff under typical rainfall conditions in southern Louisiana

Atrazine and metolachlor are commonly detected in surface water bodies in southern Louisiana. These herbicides are frequently applied in combination to corn, and atrazine to sugarcane, in this region. A study was conducted on the runoff of atrazine and metolachlor from 0.21 ha plots planted to corn on Commerce silt loam, a Mississippi River alluvial soil. The study, carried out over a three-year period characterized by rainfall close to the 30-year average, provided data on persistence in the surface soil (top 2.5 cm layer) and in the runoff active zone of the soil, as measured by decrease in runoff concentrations with time after application. Regression equations were developed that allow an estimate of the runoff extraction coefficients for each herbicide. Atrazine showed soil half-lives in the range 10.5-17.3 days, and metolachlor exhibited half-lives from 15.8-28.0 days. Concentrations in successive runoff events declined much faster than those in the surface soil layer: Atrazine runoff concentrations decreased over successive runoff events with a half-life from 0.6 to 5.7 days, and metolachlor in runoff was characterized by half-lives of 0.6-6.4 days. That is, half-lives of the two herbicides in the runoff-active zone were one-tenth to one-half as long as the respective half-lives in the surface soil layer. Within years, the half-lives of these herbicides in the runoff active zone varied from two-thirds longer for metolachlor in 1996 to one-fifth longer for atrazine in 1995. The equations relating runoff concentrations of atrazine and metolachlor to soil concentrations contain extraction coefficients of 0.009. Losses in runoff for atrazine were 5.2-10.8% of applied, and for metolachlor they were 3.7-8.0%; atrazine losses in runoff were 20-40% higher than those for metolachlor. These relatively high percent of application losses indicate the importance of practices that reduce runoff of these chemicals from alluvial soils of southern Louisiana.     

Microbial toxicity and impacts on soil enzyme activities of pesticides used in potato cultivation

In the conventional cultivation of potatoes, weed control and the control of potato late blight caused by Phytophthora infestans are carried out by the application of herbicides and fungicides. We investigated the impacts of the herbicides metribuzin and linuron and the fungicide fluazinam on soil microbiota in microcosms, in mesocosms and in the field. The toxicity of each pesticide in solution was assessed using the luminescent bacteria test and in soil by a solid phase modification. In microcosm tests, the microbial activity and biomass were estimated by measuring several soil enzyme activities together with soil ATP content. In the mesocosm tests, the separate addition of each pesticide and the simultaneous use of all the pesticides were investigated. We monitored the impacts on ten different soil enzyme activities and measured soil toxicity with the luminescent bacteria test separately in the 5 cm top layer and in the layer from 5 to about 20 cm below the surface. During one season, the impact of the use of pesticides was monitored in the field in plots receiving pesticides for the third consecutive year and in control plots cultivated without the use of pesticides for the 3 preceding years. The pesticide concentrations were monitored in each experiment. The luminescent bacteria toxicity test revealed a strong inhibition by fluazinam. In microcosms the herbicides increased several enzyme activities but metribuzin inhibited luminescence in the bacterial test. Fluazinam was highly toxic in microcosms. In the mesocosm with combined use of pesticides, decreased activities of some enzymes were observed first in the surface soil and at harvesting also deeper in the soil. In the mesocosm experiment with separate use of pesticides, less impacts were observed. In the field experiment the pesticides decreased seven enzyme activities, when calculated per soil fresh weight but activities of four enzyme decreases if calculated per soil organic matter. Controlling weeds by herbicides decreased weed growth and the decreases in enzyme activities were interpreted to be due to the lack of the stimulating impact of weed roots. A strong inhibition in the soil toxicity test and continuing bioavailability of fluazinam were detected throughout the experiments even after winter in the field.     

Dissipation of nicosulfuron and rimsulfuron in surface soil

Field and soil fortification studies were conducted to evaluate the half-lives (DT(50)) of nicosulfuron and rimsulfuron in a Sequatchie silt loam surface soil. The dissipation of each herbicide was also evaluated with the two compounds applied simultaneously, which is a typical application method used in corn production. Field studies in two years indicated that both herbicides alone and in mixture disappeared quickly, with all DT(50) < 6 days. Environmental conditions including warm, moist soil, and a soil pH of 5.7 encouraged rapid herbicide dissipation. Rapid degradation was observed under laboratory conditions using this same soil, with all DT(50) < 3 days. This research indicated minimal risk of carry-over to subsequent rotational crops and minimal residual weed control from these herbicides when applied to a silt loam soil under ambient climatic conditions in Tennessee.     

Atrazine and metolachlor degradation in subsoils

Degradation of atrazine [2-chloro-4-etylamino-6-isopropylamino-1,3,5-triazine] and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)-acetamide] in sterile and non-sterile soil samples collected at two different soil depths (0-20 and 80-110 cm) and incubated under aerobic and anaerobic conditions was studied. Under aerobic conditions, the half-life of atrazine in non-sterile surface soil was 49 days. In non-sterile subsoil, the half-life of atrazine (119 days) was increased by 2.5 times compared in surface soils and was not statistically different from half-lives in sterile soils (115 and 110 days in surface soil and subsoil, respectively). Metolachlor degradation occurred only in non-sterile surface soil, with a half-life of 37 days. Under anaerobic conditions, atrazine degradation was markedly slower than under aerobic conditions, with a half-life of 124 and 407 days in non-sterile surface soil and non-sterile subsoil, respectively. No significant difference was found in atrazine degradation in both sterile surface soil (693 days) and subsoil (770 days). Under anaerobic conditions, degradation of metolachlor was observed only in non-sterile surface soil. Results suggest that atrazine degraded both chemically and biologically, while metolachlor degraded only biologically. In addition, observed Eh values of soil samples incubated under anaerobic conditions suggest a significant involvement of soil microorganisms in the overall degradation process of atrazine under anaerobic conditions.     

Simultaneous determination of alachlor, metolachlor, atrazine, and simazine in water and soil by isotope dilution gas chromatography/mass spectrometry

A multiresidue method was developed for the simultaneous determination of low parts per billion (ppb) concentrations of the herbicides alachlor, metolachlor, atrazine, and simazine in water and soil using isotope dilution gas chromatography/mass spectrometry (GC/MS). Known amounts of 15N,13C-alachlor and 2H5-atrazine were added to each sample as internal standards. The samples were then prepared by a solid phase extraction with no further cleanup. A high resolution GC/low resolution MS system with data acquisition in selected ion monitoring mode was used to quantitate herbicides in the extract. The limit of detection was 0.05 ppb for water and 0.5 ppb for soil. Accuracy greater than 80% and precision better than 4% was demonstrated with spiked samples.     

Multi-Year Measurements of Field-Scale Metolachlor Volatilization

Volatilization is a critical pathway for herbicide loss from agricultural fields, and subsequently deposited downwind from the edge of the field. To better understand the volatilization process, field-scale turbulent volatilization fluxes of metolachlor (2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide) were quantified for 13 consecutive years using a combination of herbicide concentration profiles and eddy diffusivities derived from turbulent fluxes of heat and water vapor. Site location, type of herbicides, and agricultural management practices remained unchanged during this study in order to evaluate the effect of soil moisture on metolachlor volatilization. Twenty gravimetric surface soil moisture samples (0–5 cm) were collected immediately after herbicide application and then at 0430 hours each morning to determine the impact of surface moisture on herbicide volatilization. Five days after application, cumulative herbicide volatilization ranged from 5 to 63% of that applied for metolachlor. Metolachlor volatilization remained an important loss process more than 5 days after application when the soil surface was moist. Conversely, if the soil surface was dry, negligible volatilization occurred beyond 5 days. Furthermore, the total amount of metolachlor volatilized into the atmosphere increased exponentially with surface soil water content during application (r ²?=?0.78). Metolachlor volatility was found to be governed largely by surface soil moisture.     

Phytoremediation of metolachlor by transgenic rice plants expressing human CYP2B6

We introduced the human cytochrome P450 gene CYP2B6 into rice plants (Oryza sativa L. cv. Nipponbare), and the CYP2B6-expressing rice plants became more tolerant to various herbicides than nontransgenic Nipponbare rice plants. In particular, CYP2B6 rice plants grown in soil showed tolerance to the chloroacetanilide herbicides alachlor and metolachlor. We evaluated the degradation of metolachlor by CYP2B6 rice plants to confirm the metabolic activity of the introduced CYP2B6. Although both CYP2B6 and nontransgenic Nipponbare rice plants could decrease the amount of metolachlor in plant tissue and culture medium, CYP2B6 rice plants could remove much greater amounts. In a greenhouse, the ability of CYP2B6 rice plants to remove metolachlor was confirmed in large-scale experiments, in which these plants appeared able to decrease residual quantities of metolachlor in water and soil.     

未来气候情景下农牧交错带不同灌溉水平马铃薯产量和水分利用效率

未来气候变化对农牧交错带不同灌溉水平马铃薯产量和水分利用的影响鲜有研究。该研究基于农牧交错带张北和武川站不同灌溉条件下大田试验数据评估了APSIM-Potato模型的适应性;基于33个全球气候模式(global climate model,GCM)通过统计降尺度方法获得的未来2个气候情景(RCP4.5和RCP8.5)逐日气候数据驱动APSIM-Potato模型,模拟未来气候变化对不同灌溉水平(灌1水、灌2水、灌3水和灌4水)马铃薯产量和水分利用的影响。结果表明:APSIM-Potato模型能够较好地模拟2个站点马铃薯产量和土壤水分动态。2个站点实测产量和模拟产量的相对误差均小于22.6%,实测土壤水分和模拟土壤水分相对均方根误差均小于18.1%。基于33个GCM模拟结果,2030 s、2060 s和2090 s马铃薯生育期温度、CO2浓度、总降水量和总辐射量相比于基准期(1981-2010)均呈增加趋势。相比于基准期灌1水、灌2水、灌3水和灌4水马铃薯产量,张北站和武川站在RCP4.5情景下均有提升,张北站为4.1%~36.2%,武川站为2.5%~13.6%。RCP8.5情景下,2个站点分别提升3.1%~36.8%和3.1%~38.5%。且2个气候情景下均是灌1水情景下马铃薯产量提升最高。2个气候情景下,马铃薯水分利用效率在2030 s-2090 s均呈增加趋势。研究结果表明未来气候变化对农牧交错带地区马铃薯产量和水分利用效率具有积极影响,未来气候情景下该地区更适宜灌溉马铃薯的生产。     

Pollution induced community tolerance (PICT) and analysis of 16S rRNA genes to evaluate the long-term effects of herbicides on methanotrophic communities in soil

There is an increasing interest in agricultural systems in which the use of herbicides is forbidden. Therefore, soils treated with herbicides atrazine and metolachlor for the last 20 years were compared with soil samples from the same field that had never been treated (control soil). We determined the pollution induced community tolerance (PICT) by evaluating the methane oxidation capacity of soil samples after adding increasing amounts of a methane oxidation inhibitor, 2,4‐dichlorophenoxyacetic acid (2,4‐D). Denaturing gradient gel electrophoresis (DGGE) of 16S rRNA genes assessed whether the soil methanotrophic community differed between the two treatments. Addition of 60 µg 2,4‐D per g soil clearly inhibited methane oxidation in both soils but increased the time needed to oxidize 5% methane in the headspace by 250% for the control soil compared with 175% for the herbicide‐treated soil. This indicates that the soil with a long‐term herbicide history had a greater tolerance to the methane oxidation inhibitor than did the control soil. The DGGE of 16S rRNA genes amplified directly from soil community DNA could also distinguish the two treatments. The banding patterns of the Type I methanotrophs contained fewer bands in the herbicide‐treated soil. It seems that both the PICT approach and DGGE analysis are effective assays to distinguish a long‐term herbicide‐treated soil from an untreated soil.