拖拉机动力输出轴动态转矩载荷谱编制与验证

拖拉机动力输出轴(power take-off, PTO)室内台架耐久性试验中转矩加载主要以静态加载或静态逐级加载方式为主,这种加载方式输出的载荷与PTO实际作业中承受的载荷动态特性不同,导致试验中PTO的失效形式及测试寿命与实际作业中存在差异。针对此问题,该文对多工况下PTO动态转矩载荷谱编制方法进行研究,测取了沙土、黏土2种土壤类型下旋耕、驱动耙典型作业的PTO转矩,利用希尔伯特黄算法对转矩进行预处理,采用四点循环雨流计数法对转矩均幅值进行频次统计,利用散点矩阵统计方法分析4种作业工况均值、幅值相关性及均值、幅值分布类型。基于Miner法则及轴类20CrMnTi修正S-N曲线,在损伤概率50%、相对误差5%、置信水平95%的统计条件下,确定了转矩样本容量。利用时域外推方法对PTO转矩数据进行外推。以阈值区间内峰谷值均值差的方差为指标,检验了外推过程中选取的阈值造成峰谷值均值波动的可能性。对比外推1次后载荷时间历程与原始载荷时间历程变化趋势。在时域频次外推因子为240、转矩累计频次达到106、平均加权4类转矩时,得到PTO动态转矩载荷谱。利用编制的动态载荷谱,驱动拖拉机传动系动态加载试验台对PTO进行台架耐久性试验,试验结果显示,PTO发生失效的时长为642 h,失效形式为PTO轴头花键磨损,失效时间、失效形式与实际作业一致,验证了动态转矩载荷谱的有效性。     

Measurement of operator exposure to power take-off driven augers

Prior studies at Purdue University have shown that PTO entanglements occur most frequently on portable grain augers. A research project was conducted to measure operator exposure to PTO components and document work patterns during the use of grain augers. Information on the methodologies used to measure operator exposure is presented along with data on exposure to conventional grain augers while unloading from trucks and wagons, extended dump hopper augers, and swing-away hopper augers. It was found that operators had a higher exposure time to operating PTO components when the driveline was located on the right side of the grain auger, as one stands facing the hopper end of the auger, than on the left side of the grain auger when using conventional grain augers and grain trucks. It was determined that this added exposure was due to the position of the driver's door of the truck, the natural path of the driver from the operator's seat to the rear of the truck, and the movement of the truck body into the workspace when tilted. Of all scenarios examined, operators had the highest exposure time when using conventional grain augers and gravity-flow grain wagons. Operators had no recorded exposure time when operating swing-away hopper augers. Recommendations were made based on the observations of this study for reducing operator exposure through increased awareness of hazards and reconfiguration of the way augers are incorporated into grain handling operations.     

Artemisia dracunculus L. (tarragon): a critical review of its traditional use, chemical composition, pharmacology, and safety

Artemisia dracunculus L. (tarragon) has a long history of use as a spice and remedy. Two well-described "cultivars" (Russian and French) are used widely and differ in ploidy level, morphology, and chemistry. Key biologically active secondary metabolites are essential oils (0.15-3.1%), coumarins (>1%), flavonoids, and phenolcarbonic acids. In vivo studies mainly in rodents, particularly from Russian sources, highlight potential anti-inflammatory, hepatoprotective, and antihyperglycemic effects. Despite concerns about the toxic effects of two of its main constituents, estragole (up to 82%) and methyleugenol (up to 39%), no acute toxicity or mutagenic activity has been reported at doses relevant for human consumption. Water extracts of A. dracunculus contain very low amounts of estragole and methyleugenol and, therefore, are considered to pose a very limited risk. Overall, a stronger focus on clinical studies and precise taxonomic and phytochemical definition of the source material will be essential for future research efforts.     

山地农业生态系统持续发展的有效途径——坡地农业技术

本文简述了坡地农业技术(SALT)的原理和内容，分析了该技术在治理水土流失和大强度就地解决有机质投入，提高生物生产力和改善生态环境中的作用，指出坡地农业技术是山地农业生态系统持续发展的一个有效途径。     

Relative risk of surface water pollution by E. coli derived from faeces of grazing animals compared to slurry application

Abstract. This article examines some of the factors that influence the relative risk of Escherichia coli pollution of surface waters from grazing animals compared to cattle slurry application. Drainage water from pipe‐drained plots grazed with sheep (16 sheep + lambs per hectare) from 29 May to 17 July 2002 had average E. coli counts of 11 c.f.u. mL^?1 or 0.4% of estimated E. coli inputs over the grazing period. Drainage water from plots on the same site treated with cattle slurry (36 m³ha^?1 on 29 May 2002) had lower average E. coli counts of 5 c.f.u. mL^?1 or 0.03% of estimated faecal input. Sheep (16 lambs per hectare) grazing under cooler, moister conditions from 24 September to 3 December 2001 gave drainage water with much higher average E. coli counts of 282 c.f.u. mL^?1 or 8.2% of estimated input, which is more than twice the average E. coli counts previously reported under such conditions (Vinten et al. 2002 Soil Use and Management 18, 1–9). Laboratory studies of runoff from soil slabs after slurry application showed that the mobility of E. coli in surface soil decreased with time, suggesting that increased attachment to soil or migration to ‘immobile’ water also provides at least part of the physical explanation for the relatively higher risk of pollution from grazing animals compared with slurry. Sampling for E. coli in field drainflow and in streamwater during a storm event in the predominantly dairy Cessnock Water catchment, Ayrshire, Scotland supported the hypothesis that E. coli transport is linked to grazing animals. For a 7‐mm rainfall event, roughly 14% of the estimated daily input from grazing livestock was transported to the river, even though little slurry spreading had occurred in the catchment in the previous month. Spot sampling of field drains in grazed fields and silage fields in the same catchment also showed that grazing animals were the principal source of E. coli and faecal streptococci.     

The effect of nitrification inhibitors on the nitrous oxide (N2O) release from agricultural soils—a review

The use of nitrification inhibitors (NI) is a technique which is able to improve N fertilizer use efficiency, to reduce nitrate leaching and to decrease the emission of the climate‐relevant gas N₂O simultaneously, particularly in moderately fertilized agricultural systems adapted to plant N demand. The ammonia monooxygenase (AMO) is the first enzyme which is involved in the oxidation of NH$ _4^+ $ to NO$ _3^ - $ in soils. The inhibition of the AMO by NIs directly decreases the nitrification rate and it reduces the NO$ _3^- $ concentration which serves as substrate for denitrification. Hence, the two main pathways of N₂O production in soils are blocked or their source strength is at least decreased. Although it has been shown that archaea are also able to oxidize NH₃, results from literature suggest that the enzymatic activity of NH₃ oxidizing bacteria is the most important target for NIs because it was much stronger affected. The application of NIs to reduce N₂O emissions is most effective under conditions in which the NI remains close to the N ‐ fertilizer. This is the case when the NI was sprayed on mineral ‐ N fertilizer granules or thoroughly mixed with liquid fertilizers. Most serious problems of spatial separation of NI and substrate emerge on pasture soils, where N₂O hotspots occur under urine and to a lesser extent under manure patches. From the few studies on the effect of different NI quantities it seems that the amount of NI necessary to reduce N₂O emissions is below the recommendations for NI amounts in practice. NIs can improve the fertilizer value of liquid manure. For instance, the addition of NIs to slurry can increase N uptake and yield of crops when NO$ _3^ - $ ‐ N leaching losses are reduced. It has clearly been demonstrated that NIs added to cattle slurry are very effective in reducing N₂O as well as NO emissions after surface application and injection of slurry into grassland soils. In flooded rice systems NIs can reduce CH₄ emission significantly, whereas the effect on CO₂ emission is varying. On the other hand, as an effect of the delay of nitrification by NIs, NH₃ emission might increase when N fertilizers are not incorporated into the soil. As compared to other measures NIs have a high potential to reduce N₂O emissions from agricultural soils. Further, no other measure has so consistently been proofed according its efficiency to reduce N₂O emissions. From the published data [Akiyama et al. ( 2010 ) and more recent data from the years 2010–2013; 140 data sets in total] a reduction potential of approx. 35% seems realistic; however, further measurements in different management systems, particularly in regions with intense frost/thaw cycles seem necessary to confirm this reduction potential. These measurements generally should cover a whole annual cycle.     

Relative sensitivity of survival,growth and reproduction of Eurytemora affinis (Copepoda) to assessing polluted estuaries

Groups of Eurytemora affinis were held in flow-through chambers and exposed to ambient water from moderately (Station 1) and heavily (Station 2) polluted sites in Chesapeake Bay tributaries. A control group was held in identical chambers supplied with water from a clean site. Survival, growth and reproduction were assessed after 10 days exposure. At the moderately polluted site, an additional treatment consisting of a 50∶50 mix of control and ambient water was also run. Survival of E. affinis was not a reliable indicator of water quality. Growth was indicative of water quality at each station, but not between stations. Relative fecundity was the best indicator of water quality within and between stations. At Station 1, the relative fecundity was 2.6, 4.2 and 10.0 in ambient, 50∶50 mix and control water, respectively. At Station 2, the relative fecundity was 0.8 and 10.0 in ambient and control water, respectively.     

Elemental status (Cu,Mo, Co,B, S and Zn) of Scottish agricultural soils compared with a soil‐based risk assessment

Concentrations of six elements copper (Cu), molybdenum (Mo), cobalt (Co), boron (B), sulphur (S) and zinc (Zn) are summarized for Scottish advisory soil samples collected during the period 1996–2008. Accompanying cropping information indicated that the majority of samples collected for Co analysis were from grassland compared with B, S and Zn where sampling was predominantly prior to either potatoes or vegetables. The proportion of samples measured as potentially deficient [very low (VL) or low categories] were 80% for Co, compared with 50, 40, 38, 25 and 18% for Mo, S, Zn, Cu and B, respectively. Only S displayed a significant decline (ca. 2 mg S/kg) over this 13‐year period. However, comparison of Cu and Co data with some collected from an earlier time period (1973–1980) suggested little difference for Cu but a smaller number of VL and low Co status samples. A predicted risk assessment using soil parent material, texture and drainage status suggested that 22, 38 and 40% of the agricultural area of Scotland were at a high, medium and low risk of Cu deficiency; comparable numbers for Co were 48, 30 and 22%. The reliability of the risk assessment was tested using a sub‐set of advisory samples with specific information on soil series. Of the soils predicted to have a high risk of Cu deficiency, 52% actually fell into the ‘deficient’ status. A similar comparison for Co indicated 90% of the samples predicted as having a high risk of deficiency were measured as VL or low.     

1999年春季(3～5月)天气对我国农业生产的影响

１９９９年春季全国大部地区气温偏高,降水偏少,总的天气特点为开春早,回暖迟,前春少雨干旱,仲、后春雨水充沛,大面积干旱主要发生在３￣４月,大部分地区气温波动较为明显,中东部农区初春出现倒春寒天气,冬小麦,油菜受到不同程度的冻害,早稻播种期亦有所推迟;西北地区西部仲春出现强寒潮天气,使春播作物遭受严重冻害;东北地区大部气温回升慢,春播期偏晚、作物生长迟暖。入春后北方冬麦区先后出现几场较大范围降水,使     

Choice of methods for soil microbial community analysis: PLFA maximizes power compared to CLPP and PCR-based approaches

Polyphasic studies that used phospholipid fatty acid analysis (PLFA) in conjunction with community level physiological profiling (CLPP) or PCR-based molecular methods were analyzed in order to evaluate the power of each strategy to detect treatment effects on soil microbial community structure (MCS). We found no studies where CLPP or PCR-based methods differentiated treatments that were not also differentiated by PLFA. In 14 of 32 studies (44%), PLFA differentiated treatments that were not resolved by CLPP analysis. In 5 of 25 studies (20%), PLFA differentiated treatments that were not resolved by PCR-based methods. We discuss PLFA, CLPP, and PCR-based methods with respect to power to discriminate change in MCS versus potential for characterization of underlying population level changes.     

Involvement of Enchytraeidae (Oligochaeta) in soil structure evolution in agricultural fields

Summary The effects of enchytraeid activity on soil structure were recorded in a field study on population dynamics in agro-ecosystems and in a field experiment, using artificially compounded soil cores. It was established that 21–35% of the enchytraeid population contained mineral grains. The estimated transport of mineral material in the upper 0.4 m amounted to 0.001–0.01% of the bulk soil per year. In experimental cores with enchytraeids present, the air permeability, volume of pores in the size class corresponding to the enchytraeid body width, and the proportion of aggregates corresponding to the size of their fecal pellets were higher than in cores without enchytraeids.Dedicated to the late Prof. Dr. W. Kühnelt Communication no. 15 of the Dutch programme on soil ecology of arable farming systems     

Response of an agricultural soil to pentachlorophenol (PCP) contamination and the addition of compost or dissolved organic matter

The response of a fresh, agricultural soil when contaminated with pentachlorophenol (PCP) and supplemented with compost (C) or dissolved organic matter (DOM) was studied in the laboratory. The concentration of PCP and the changes in various functionally related properties (i.e. microbial biomass, basal respiration, soil hydrolase and oxidoreductase activity) were measured over 150 d. Variations in the main physical and chemical properties of the soils were also monitored. Two different doses of compost (C1 = 0.27% and C2 = 0.83%, corresponding to 10 and 30 t ha⁻¹, respectively) or DOM (D1 = 0.07% and D2 = 0.2%) equivalent to the carbon content of the two compost doses C1 and C2 were used and the following five systems were investigated: soil (S), soil–compost (S-C1 and S-C2) and soil–DOM (S-D1 and S-D2). PCP concentrations declined progressively and significantly with time. This effect was most pronounced for the soils amended with the lower compost dose C1 (S-C1) and with the two DOM (S-D1 and S-D2) amounts. Significantly reduced amounts of PCP were extracted after its 500-d residence in the various systems. Higher amounts of the residual PCP were extracted from the humic acids (HA), fulvic acids (FA) and humin–mineral (HU) fractions of the 500 d aged samples than from the same unfractionated samples, indicating that the residual PCP preferentially accumulated in the organic fractions of soil. The soil showed an endogenous microbial activity as indicated by basal respiration, microbial biomass and all the enzymatic activities tested (dehydrogenase, glucosidase, phosphatase, arylsulphatase and urease). Addition of the PCP severely depressed some of the tested biochemical properties suggesting an inhibitory effect on microbial activity. Conversely, higher basal respiration, and similar β-glucosidase and phosphatase activities were measured in comparison with the controls. No significant effects were observed following the addition of two doses of the compost or the DOM. Fungal colonies belonging to the taxonomic group of Ascomycetes and identified as Byssochlamys fulva developed with time in all the PCP-contaminated samples. Growth of B. fulva in vitro in the presence of PCP showed that the isolate was tolerant to 12.5 and 25 mg l⁻¹ PCP and degraded 20% of its initial concentration in 8 d. Overall, the results indicate that many complex processes occurred in the contaminated soil and combinations of these determined the response to PCP contamination. The sorption of PCP to the soil matrix (which increased with time) and its degradation/transformation by indigenous soil microbial activity were likely involved. Both the processes appeared to be favoured by the presence of dissolved organic matter.     

Reductive biogenic transformation of Fe(III)-containing phyllosilicates (review of publications)

Microorganisms are capable of reducing the structural Fe(III) of some phyllosilicates, i.e., montmorillonite, nontronite, and illite. Two reduction results are possible. For the low-ferruginous minerals, the solid-phase partial reduction of the structural Fe(III) does not cause any decay of particles. In this case, reduction leads to a partial dehydroxylation of the lattice and magnetic disordering of the mineral, as well as to changes in the layer packaging, the crystallization degree, the texture, the color, the surface charge, and the cation-exchange capacity. Except for dehydroxylation and the changing Fe oxidation status, the transformations of minerals’ properties are irreversible for the most part. In highly ferruginous phyllosilicates, the structural Fe(III) reduction leads to the particle dissolution. As a result of microbial reductive dissolution of crystallized nontronite, new amorphous minerals are formed, i.e., aluminosilicates with an elevated Al/Si ratio, Si globules, and Fe hydroxides. Another biogenically crystallized Si mineral (tridymite βSiO₂) is formed in light-textured soils and sediments after smectite decomposition. The bacterial reduction of highly ferruginous illite leads to transformation of the shape of some particles: initially acicular illite crystals were transformed into plates. The amorphous structure is formed in illite particles contacting with bacterial cells. The solid-phase reduction of structural Fe(III) does not lead to particle dissolution in the case of low-ferruginous illite.     

漳州土壤中有机氯农药残留研究

A soil survey was conducted in Zhangzhou City,an important agricultural region in south of the Fujian Province,China.93 surface soil samples were collected in the paddy fields,vegetable lands,orchards and tea plantations from Zhangzhou City.An additional soil profile was sampled in a paddy field as previous research had indicated high concentrations of organochlorine pesticides(OCPs) in the paddy fields.Dichlorodiphenyltrichloroethanes(DDTs) ranged from 0.64-78.07 ng g 1 dry weight and hexachlorocyclohexanes(HCHs) ranged from 0.72-30.16 ng g 1 dry weight in the surface soil of the whole study region.Ratios of α-HCH/γ-HCH < 4 and o,p-DDT/p,p-DDT > 1 in all soil samples suggested that lindane and dicofol were widely applied in this region in the past.Concentrations of HCHs and DDTs in soils from the four land use types followed the orders:paddy fields > vegetable lands > tea plantations > orchards and tea plantations > orchards > paddy fields > vegetable lands,respectively.Analyses of the data showed no correlation(r < 0.1) between elevation and OCPs contents in paddy fields,orchards and vegetable lands,indicated no significantly different features in distribution of HCHs and DDTs in the soils from low lying plains and mountains and the unsystematic usage of OCPs,and highlighted the fragmented nature of agricultural production in Zhangzhou,as well as the reemission of OCPs from the soils,where high OCPs concentrations were found,in Longhai of Zhangzhou.In addition,no obvious relationship between the OCPs and total organic carbon(TOC)(r < 0.3) was observed in the soil profile.The mean contribution of dicofol in total DDTs was 66% in the whole Zhangzhou region.The approximate burdens of HCHs and DDTs in the surface layer of 0-20 cm were 0.44 and 1.55 t,respectively.The storage of both HCHs and DDTs in soil surface layer(0-20 cm) accounts for 40% burden of the soil layer of 0-50 cm(1.10 t HCHs and 3.87 t DDTs),in which the highest concentrations of OCPs were observed in soil profile.     

Study of landscape- agrogeochemical balance of nutrients in agricultural regions (Part I: Phosphorus)

The P balance in the watersheds of four small rivers of the Oka Valley, U.S.S.R., was investigated. A positive P balance was observed for all four watersheds. Application rates of P fertilizers and accumulation of P in soils were highly correlated (r = 0.997). However, no correlation between the level of application of mineral P fertilizers and P concentration in the groundwater was found. The concentration of P in groundwater was found to be dependent upon the content of organic matter in the soils and the amount of FYM applied. It may be assumed that polyphosphates (the biosynthesis of which is stimulated by the available organic matter and orthophosphates applied) are of great importance for P migration in soils.     

Changes in surface structure (crusting) after application of sewage sludge and pig slurry to cultivated agricultural soils in Northern Italy

The first results of a cooperative research project on changes in cultivated agricultural topsoils after treatment with sewage sludge and pig slurry are discussed for a silty clay soil (Vertic Xerochrept) and a sandy loam soil (Typic Psammaquent). Such changes are expressed in the surface structure, including crusts, of the soils and have a direct effect on their fertility. To measure these changes, special attention was paid to porosity characteristics; especially increases in porosity after application of organic manures to agricultural soils with crusting problems. Light microscopy, SEM-EDXRA (scanning electron microscopy — energy dispersive X-ray analysis) and Quantimet (electro-optical image analysis) were applied and allowed quantitation and visualisation of pores. Initial results clearly demonstrate that the porosity of the topsoil increased after treatment with urban refuse or pig slurry and that crusting decreased.     

Contribution of rhizomicrobial and root respiration to the CO2 emission from soil (A review)

Separate determination of root respiration and rhizomicrobial respiration is one of the most interesting, important, and methodologically complicated problems in the study of the carbon budget in soils and the subdivision of the CO₂ emission from soils into separate fluxes. In this review, we compare the main principles, the advantages and disadvantages, and the results obtained by the methods of component integration, substrate-induced respiration, respiratory capacity, girdling, isotope dilution, model rhizodeposition, modeling of the ¹⁴CO₂ efflux dynamics, exudates elution, and the δ¹³C measurements of the microbial biomass and CO₂. Summarizing the results of the determinations performed by these methods, we argue that about 40% of the rhizosphere CO₂ efflux is due to root respiration and about 60% of this efflux is due to the respiration of microorganisms decomposing root exudates.     

Importance of Soil Organic Matter (SOM) for Biomass Production and Environment (a review)

The aim of sustainable agricultural land use is to reach high and rising crop yields and to minimise environmental pollution. Soil organic matter (SOM) plays a key role in maintaining soil productivity and also in protection of environment. At least two SOM fractions can be distinguished, one being relatively inert, the other being decomposable. High yields are only attainable on an environmentally acceptable way in combination of organic and mineral fertilization. The ranges for the optimal content of the decomposable organic carbon is between 0.2 and 0.6% and that of nitrogen 0.02 and 0.06%. The hot water extractable carbon has proved to be an appropriate criterion for the characterisation of the decomposable carbon. When considering the current state of knowledge consistently, the use of mineral fertiliser has a positive effect on the environment and supports a considerable gain of energy by the cultivated crops. Too high humus content in soil can contribute to environmental pollution. Between organic carbon content and soil physical properties there is nearly functional relation.     

Transformation of forest soils in Iowa (United States) under the impact of long-term agricultural development

The evolution of automorphic cultivated soils of the Fayette series (the order of Alfisols)—close analogues of gray forest soils in the European part of Russia—was studied by the method of agrosoil chronosequences in the lower reaches of the Iowa River. It was found that the old-arable soils are characterized by an increase in the thickness of humus horizons and better aggregation; they are subjected to active biogenic turbation by rodents; some alkalization of the soil reaction and an increase in the sum of exchangeable bases also take place. These features are developed against the background of active eluvial-illuvial differentiation and gleyzation of the soil profiles under conditions of a relatively wet climate typical of the ecotone between the zones of prairies and broadleaved forests in the northeast Central Plains of the United States.