土壤结构、水分与植物根系对土壤能量状态的影响

土壤的能量状态反应土壤水分对植物的有效性 ,常以土壤水势来表示。通过对影响土壤水势因子的分析 ,给出土壤水势与土壤结构及含水率关系的表达式。当土壤不含水分时 ,影响土壤水势的因子主要为土壤的结构 ;当土壤含有水分时 ,由于土壤水分中和了部分毛管力 ,随着土壤水含水量的增加 ,土水势必然升高 ,所以 ,土壤结构与土壤含水率决定着土水势的高低。另外由于植物根系影响土壤结构与含水率 ,所以根系对土壤水势的影响也不可忽略。

水稻节水高产灌溉模式及土壤水分能量调控标准研究

198 9～ 1998年在沈阳农业大学灌溉试验场通过盆载、蒸渗仪、小区及大田进行试验研究 ,分析了水稻的需水规律及稻田土壤水分能量的变化特点 ,论述了土壤水分状况与水稻腾发强度之间的关系、不同灌溉模式对水稻腾发量的调控作用以及水分胁迫对水稻产量的影响 ,提出了水稻节水高产灌溉模式和土壤水分能量调控标准。

水稻节水高产灌溉模式及土壤水分能量调控标准研究(英文)

根据土壤—植物—大气连续系统原理 ,1989～ 1998年在沈阳农业大学灌溉试验场通过盆载、蒸渗仪、小区及大田进行试验 ,分析了水稻的需要水规律及稻田土壤水分能量的变化特点 ,论述了土壤水分状况与水稻腾发强度之间的关系、不同灌模式对水稻腾发量的调控作用以及水分胁迫对水稻产量的影响 ,提出了水稻节水高产灌溉模式和土壤水分能量调控标准。

土壤水分能量与兴安落叶松播种苗生长关系的研究

为了研究兴安落叶松播种苗在出苗期、生长初期和速生期所需要的最佳土壤水分能量水平及影响生长的上、下限值,使用张力计控制3～4个土壤水分能量(土壤水吸力)水平等级(处理)。结果说明在出苗期对场圃发芽率、发芽势、平均发芽速度和 L/H 比的最佳土壤水分能量水平是土壤水吸力为10～20kPa;当土壤水吸力为50～73.3kPa 时,就严重影响出苗;当土壤水吸力低于10kPa 时,对苗木根系产生不利影响。在生长初期最佳土壤水分能量水平是土壤水吸力为30～40kPa;当土壤水吸力为10～20kPa 或50～73.3kPa 时,就明显影响苗木生长。在速生期对苗、地径、根系,生物量生长最佳的土壤水分能量水平是土壤水吸力为10～20kPa;当土壤水吸力为50～73.3kPa时。

不同土壤水分能量及气象因子对水稻腾发量的影响

采用盆栽试验,探讨了不同土壤水分能量和气象因子对水稻腾发量的影响。在水稻的不同生育阶段进行不同程度的土壤水分能量调控,分析受控生育阶段水稻腾发量的变化及其对产量的影响,及受控生育阶段内腾发量的典型日变化规律;利用典型日内充分供水条件下的腾发量数据及相应时段的气象资料,通过逐步回归建立了多元线性回归模型。结果表明:不同生育阶段土壤水分能量调控,对水稻腾发量影响趋势相同,但对产量影响趋势不同;晴天时各处理腾发量强度曲线呈明显的单峰变化,阴天时则无明显规律;诸气象因子中总辐射强度、相对湿度和风速进入了逐步回归模型。在气象因子相同的情况下,腾发量的大小由各处理的土壤水分能量大小决定;相同土壤水分能量下,在水稻腾发量中起主要作用的气象因子是辐射强度、相对湿度和风速。

落叶松胡桃楸人工混交林下土壤团聚程度和水分能量特征分析

该文对东北东部山区３３ａ生落叶松纯林与胡桃楸和落叶松混交林下土壤的团聚程度与水分能量特征进行了外业调查与室内分析。结果表明：胡、落混交林下土壤的水稳性团聚体和有效含水范围明显优于落叶松纯林，更有利于林木生长。混交林土壤和纯林土壤相比，０～１０ｃｍ、１０～２０ｃｍ、２０～３０ｃｍ三层水稳性团聚体含量前者较后者分别提高了１．４％、０．３％、２．１％，平均重量直径前者分别是后者的１２０％、１１９％和１０７％，有效含水范围前者分别是后者的１３４％、１１５％和１１３％。

故河道壤质沙土土壤水分调控与节水灌溉技术

本项全面、系统地研究了壤质沙土的土壤质地、结构、水分特性、有效水的供给能力、数量及对作物生长的影响,从土壤水分能量角度进行了量化说明,并初步引入分形理论定量描述了不规整几何形体的土壤粒径分布特征。根据沙土的水分特性与植株生长状况,确定了沙土小麦。

紫茎泽兰能源化利用研究

详细介绍了一种紫茎泽兰能源化利用的新工艺。通过榨汁、振荡培养、离心、厌氧发酵等步骤,将新鲜紫茎泽兰制作成为农残降解剂和沼渣肥,农残降解剂残渣经过厌氧消化,发酵结束后获得的沼渣也具有一定能量,再施入土壤后可以提高土壤的能量水平。联通的工艺流程可以提高紫茎泽兰的利用效率,增加土壤总能量水平,从能量梯级利用角度,紫茎泽兰资源化的利用效率较高。对于沼渣作为肥料,本实验测定了其重金属、总养分、活菌数、杂菌率等指标,证明沼渣是一种比较理想的菌肥。

Fixed Ammonium Contents and NH Fixation Capaci-ties of Some Cnltivated Soils in China

Fixed ammonium contents and fixation capacities of some representative cultivated soils collectedfrom 16 provinces of China were studied. Results showed that the contents of fixed ammonium in soilsranged from 35 to 573 mg N kg￣(-1), with an average of 198 mg N kg￣(-1). The content of fixed ammoniumcorrelated very significantly with mica content for tropical and subtropical soils, whereas this was not thecase for soils in the temperate zone. At the end of K-exhansting experiment the fixed ammonium contentincreased in most soils studied. However, it decreased in some temperate soils. Generally, fixation of addedNH could not be found either before or after K-exhausting experiment for highly weathered soils, includingtropical soils and soils derived from granite-gneiss or Quaternary red clays in the subtropic zonet while formost soils in the Yangtze River dalta the NH fixation capacity was rather high and increased siguificantlyin the K-exhausted soils.

Bearing capacity of foundation on slope determined by energy dissipation method and model experiments

To determine the ultimate bearing capacity of foundations on sloping ground surface in practice, energy dissipation method was used to formulate the beating capacity as programming problem, and full-scale model experiments were investigated to analyze the performance of the soil slopes loaded by a strip footing in laboratory. The soil failure is governed by a linear Mohr-Coulomb yield criterion, and soil deformation follows an associated flow rule. Based on the energy dissipation method of plastic mechanics, a multi-wedge translational failure mechanism was employed to obtain the three bearing capacity factors related to cohesion, equivalent surcharge load and the unit gravity for various slope inclination angles. Numerical results were compared with those of the published solutions using finite element method and those of model experiments. The bearing capacity factors were presented in the form of design charts for practical use in engineering. The results show that limit analysis solutions approximate to those of model tests, and that the energy dissipation method is effective to estimate bearing capacity of soil slope.

Effect of Tillage and Planting Methods on the Soil Properties, Grain Drill Performance, and Wheat Yield

The effect of conservation tillage methods and seeding machines on the soil physical properties, performance of grain drill, wheat yield, and wheat yield components was evaluated. The research was conducted in a split block experimental design with twelve treatments and four replications, and a local wheat variety （Shiraz） was planted in this study. Main plots were tillage methods including： （1） primary tillage using moldboard plow without moldboard; （2） primary tillage with disk harrow; and （3） primary tillage with chisel plow. Subplots were grain drill types including： （1） planting with Taka grain drill without furrower; （2） planting with Taka grain drill having furrower; （3） planting with Hamadan Machine Barzegar grain drill having furrower and runner opener; 4） planting with grain drill having ripple opener. Parameters including mean weight diameter of clods （MWD）, soil bulk density, uniformity of seed planting depth, seed distribution uniformity, seed emergence, crop yield, and crop yield components were measured. SAS software was used to analyze the collected data and the method of benefit to cost ratio was used to compare the treatments from the economic point of view. Results indicated that tillage method had no significant effect （P = 0.05） on the measured parameters. Plant per unit area, seed emergence, uniformity of seed planting depth, and MWD were significantly affected by the grain drill type （P 〈 0.05） while, the type of grain drill had no significant effect on the rest of measured parameters. Taka grain drill without furrower had the highest uniformity of planting depth and proper soil MWD, and grain drill with ripple opener had the highest seed emergence and plant per unit area. Interaction between tillage methods and grain drill types affected the soil MWD, seed emergence, and crop yield （P 〈 0.05） in such a way that the combination of primary tillage with disk harrow and planting with grain drill having ripple opener provided the highest crop yield.

A STUDY ON THE RELATIONSHIP BETWEEN SPRING SOIL MOISTURE OVER CHINA AND EAST ASIA SUMMER MONSOON

The correlation analysis has been used to study the relationship between spring soil moisture over China and East Asian summer monsoon (EASM). It is shown that EASM has a strong positive correlation with spring soil moisture over southwest China and the Great Bend region of the Yellow River. A standard soil moisture index (SMI) has been defined using the observed soil moisture of the two regions. The results show that SMI has a strong correlation with EASM. The years of strong (weak) SMI are associated with stronger (weaker) summer monsoon circulation. In the years of strong SMI, the west Pacific subtropical high is much northward in position and weaker in intensity;the westerlies zone is also more to the north. All of these make EASM circulation move northward and cause the rainfall belt to relocate to North China and Northeast China. SMI can reflect the variation of the summer rainfall anomaly over eastern China. In the years of strong SMI, the rainfall belt is mainly located over the northern part of China. However, during the weak years, the summer rainfall belt is largely located over the mid-and lower-reaches of the Yangtze River. Additionally, the SMI has obvious oscillations of quasi 4-6 years and quasi 2 years. Moreover, negative SMI predicts EASM better than positive SMI.

The Effect of Drought Occurring at Different Growth Stages on Productivity of Grain Amaranth Amaranthus cruentus G6

A greenhouse pot experiment was conducted to study the effect of drought induced at different phenological stages on growth, biomass production and yield performance of grain amaranth Amaranthus cruentus G6. After emergence seedlings were exposed to different soil water regimes： constant adequate moisture （W1） and drought （W2） throughout the growing period, drought initiated at crop inflorescence formation （W3）, drought condition during pre-inflorescence formation （W4） and treatment W5 where drought condition occurred in the period from the beginning of inflorescence formation to the beginning of flowering. Crop samples were taken at the maturity. The growth and yield performance of amaranth were assessed by measuring root length, stem height and inflorescence length, and by evaluating fresh and dry weight of plant parts, grain yield and harvest index. Drought stress initiated at different phenological stages affected the evaluated morphological parameters, assimilate allocation and grain yield. Drought throughout the growing period resulted in grain and biomass yield reduction for 51% and 50%, respectively. Water deficit during inflorescence formation appears to be critical growing stage influencing grain yield, while soil drying in the vegetative growth stages improve the assimilate allocation to the above-ground biomass and particularly to the grain.

Simulation of the Bare Soil Surface Energy Balance at the Tongyu Reference Site in Semiarid Area of North China

The performance of a I-D soil model in a semiarid area of North China was investigated using observational data from a cropland station at the Tongyu reference site of the Coordinated Enhanced Observing Period （CEOP） during the non-growing period, when the ground surface was covered with bare soil. Comparisons between simulated and observed soil surface energy balance components as well as soil temperatures and water contents were conducted to validate the soil model. Results show that the soil model could produce good simulations of soil surface temperature, net radiation flux, and sensible heat flux against observed values with the RMSE of 1.54℃, 7.71 W m^-2, and 27.79 W m^-2, respectively. The simulated volumetric soil water content is close to the observed values at various depths with the maximal difference between them being 0.03. Simulated latent heat and ground heat fluxes have relatively larger errors in relative to net radiation and sensible heat flux. In conclusion, the soil model has good capacity to simulate the bare soil surface energy balance at the Tongyu cropland station and needs to be further tested in longer period and at more sites in semiarid areas.

Influence of Composts on Agrochemical Properties of Soils of Zarafshan Valley, Salted with Magnesium Carbonates and Yield Capacity of Corn

Peculiar characteristics of soils of Zarafshan valley are salinity with carbonates. It is recommended to introduce large amount of manure or other organic fertilizers in these soils to improve soil reclamation. But currently there is no possibility to collect so many organic fertilizers in Uzbekistan. That is why other ways of production of organic fertilizers for improving soil fertility were searched. In the experiment, the influence of composts was studied, which prepared from tobacco wastes and manure on agrochemical properties of soils of Zarafshan valley, and production of composts from these industrial wastes, two salted with magnesium carbonates and yield-capacity of com. With the problems that exist in Uzbekistan can be solved at once. These include problems of environmental contamination through wastes and ensuring with organic fertilizers in the irrigated soils. Introduction of composts in the doze of 30 t.ha1 separately and on the background of mineral-NPK （nitrogen, phosphorus and potassium） fertilizers increased the humus content, total NPK and mobile nutritious substances in soil. It is proved that composts, prepared from tobacco wastes with their effect on the yield capacity and quality ofcoru production, can successfully substitute manure. Composts positively influence on the balance of nutritious substances in the system of soil-corn.

Drought shifts soil nematode trophic groups and mediates the heterotrophic respiration

As the most diverse metazoan taxa,soil nematodes serve a diversity of functions in soil food webs and thus can regulate microbial community composition and affect organic matter decomposition and nutrient turnover rates.Because nematodes depend on water flms to access food resources,drought can negatively affect nematode-microbial food webs,yet the impacts of drought on nematode diversity and abundance and how these changes may infuence food web members and their functions are hardly explored.Here,we coupled research along a drought gradient in arid and semiarid grasslands with a detailed intact plant-soil microcosm experiment to explore the patterns and mechanisms of how drought impacts nematode abundance and carbon footprint,microbial phospholipid fatty acid(PLFA)and heterotrophic soil respiration.Overall,in the feld and the microcosm experiments,we found that nematode abundance,carbon footprint and diversity,microbial PLFA and heterotrophic respiration were reduced under drier conditions.In addition,drought altered nematode and microbial community composition,through reducing the nematode channel ratio and increasing the relative fungivorous nematode abundance and the fungal to bacterial ratio.The soil decomposition channel shifted from a bacterial to a fungal pathway in response to drought,indicating decelerated heterotrophic respiration under drought.These results highlight the important contribution of soil nematodes and their associated microbial food web to soil carbon cycling.Our fndings underscore the need to incorporate key soil fauna into terrestrial ecosystem model evaluation.

Effects of Plant Functional Types,Climate and Soil Nitrogen on Leaf Nitrogen along the North-South Transect of Eastern China

We conducted a systematic census of leaf N for 102 plant species at 112 research sites along the North-South Transect of Eastern China （NSTEC） following the same protocol, to explore how plant functional types （PFTs） and environmental factors affect the spatial pattern of leaf N. The results showed that mean leaf N was 17.7 mg g^-1 for all plant species. The highest and lowest leaf N were found in deciduous-broadleaf and evergreen-conifer species, respectively, and the ranking of leaf N from high to low was： deciduous 〉 evergreen species, broadleaf 〉 coniferous species, shrubs ≈ trees 〉 grasses. For all data pooled, leaf N showed a convex quadratic response to mean annual temperature （MAT）, and a negative linear relationship with mean annual precipitation （MAP）, but a positive linear relationship with soil nitrogen concentration （Nsoil）. These patterns were similar when PFTs were examined individually. Importantly, PFTs, climate and Nsoil, jointly explained 46.1% of the spatial variation in leaf N, of which the independent explanatory powers of PFTs, climate and Nsoil, were 15.6%, 2.3% and 4.7%, respectively. Our findings suggest that leaf N is regulated by climate and Nsoil, mainly via plant species composition. The wide scale empirical relationships developed here are useful for understanding and modeling of the effects of PFTs and environmental factors on leaf N.

Modification of the land surface energy balance relationship by introducing vertical sensible heat advection and soil heat storage over the Loess Plateau

Little is known about the surface energy balance problem for a complex underlying surface.Taking data from the Loess Plateau Land-surface Processes Experiment(LOPEX) and investigating the characteristics of the surface energy balance over a complex underlying surface,this paper calculates the soil heat storage and vertical sensible heat advection,analyzes their contributions to the surface energy imbalance,and discusses the mechanism by which the vertical velocity and temperature gradient in the surface layer affect the vertical sensible heat advection transfer.We found that the vertical velocity in the surface layer provides the necessary dynamic power for vertical sensible heat advection,and a relatively strong temperature gradient is the energy source generating vertical sensible heat advection.Under an ascending condition,the effect of vertical sensible heat advection on the surface energy budget is more obvious.It is also found that when the soil heat storage term and the vertical sensible heat advection term are added to the energy balance equation,the imbalance significantly improves.The peak of average diurnal residuals decreases from 125.1 to 41.5 W m-2,the daily average absolute value of residuals falls from 59.0 to 26.4 W m-2,and the surface energy balance closure increases from 78.4% to 94.0%.

Surfactant-Enhanced Soil Washing for Removal of Petroleum Hydrocarbons from Contaminated Soils: A Review

An increase in energy demand leads to further exploration, transportation, and utilization of petroleum, which creates severe soil contamination because of recurrent accidents and oil spills. Remediation of these contaminated soils is challenging. Among many treatment methods practiced for remediation of petroleum-contaminated soils, surfactant-enhanced soil washing has been widely practiced as a preferred treatment option, as it is a fast and environmentally accepted method. In this paper, we review research undertaken on various anionic, nonionic, cationic, biological, and mixed surfactants for the remediation of petroleum hydrocarbon-contaminated soils. Upcoming surfactants like gemini and switchable surfactants are summarized. We assess the challenges and opportunities of in-situ and ex-situ soil washing, the mechanisms of surfactant-enhanced soil washing, and the criteria to follow for surfactant selection.Furthermore, we briefly discuss the operational and environmental factors affecting soil washing efficiency and soil and surfactant properties affecting surfactant adsorption. We also describe the advantages of coupling soil washing with effluent treatment and surfactant reuse challenges and opportunities. Moreover, challenges and possible new directions for future research on surfactant-enhanced soil washing are proposed.

Numerical simulation and data assimilation of the water-energy cycle over semiarid northeastern China

The default fractional vegetation cover and terrain height were replaced by the estimated fractional vegetation cover, which was calculated by the Normalized Difference Vegetation Index （NDVI） of Earth Observing System Moderate-Resolution Im- aging Spectroradiometer （EOS-MODIS） and the Digital Elevation Model of the Shuttle Radar Topography Mission （SRTM） system. The near-surface meteorological elements over northeastern China were assimilated into the three-dimensional varia- tional data assimilation system （3DVar） module in the Weather Research and Forecasting （WRF） model. The structure and daily variations of air temperature, humidity, wind and energy fields over northeastern China were simulated using the WRF model. Four groups of numerical experiments were performed, and the simulation results were analyzed of latent heat flux, sensible heat flux, and their relationships with changes in the surface energy flux due to soil moisture and precipitation over different surfaces. The simulations were compared with observations of the stations Tongyu, Naiman, Jinzhou, and Miyun from June to August, 2009. The results showed that the WRF model achieves high-quality simulations of the diurnal charac- teristics of the surface layer temperature, wind direction, net radiation, sensible heat flux, and latent heat flux over semiarid northeastern China in the summer. The simulated near-surface temperature, relative humidity, and wind speed were improved in the data assimilation case （Case 2） compared with control case （Case 1）. The simulated sensible heat fluxes and surface heat fluxes were improved by the land surface parameterization case （Case 3） and the combined case （Case 4）. The simulated tem- poral variations in soil moisture over the northeastern arid areas agree well with observations in Case 4, but the simulated pre- cipitation should be improved in the WRF model. This study could improve the land surface parameters by utilizing remote sensing data and could further improve atmospheric elements with a data assimilation system. This work provides an effective attempt at combining multi-source data with different spatial and temporal scales into numerical simulations. The assimilation datasets generated by this work can be applied to research on climate change and environmental monitoring of add lands, as well as research on the formation and stability of climate over semiarid areas.