供水压力对微孔陶瓷渗灌土壤水分运移的影响

为探明供水压力对微孔陶瓷灌水器灌水条件下土壤水分运移规律的影响,通过室内土箱模拟试验,研究了3个压力水平下的微孔陶瓷灌水器灌水时的土壤水分入渗特征。研究结果表明,微孔陶瓷灌过程中,供水压力是决定土壤水分初始入渗速率和累计入渗量的关键因素,且供水压力越大,土壤水分初期入渗速率越大,最终累计入渗量也越大;微孔陶瓷渗灌形成的湿润体轮廓为上下不对称的椭球体,湿润锋在各方向上的运移距离与时间呈幂函数关系,其中入渗向上距离水平距离向下距离,供水压力越大,水平最大入渗半径距离灌水器底部距离越远;供水压力对土壤含水分分布影响较大,供水压力越大,灌水器周围含水率越高,高含水率区域越大。在各供水压力水平下,微孔陶瓷渗灌形成的湿润体大小和含水率均能满足作物根系吸水需求。     

渗灌用黏土基微孔陶瓷灌水器入渗性能研究

针对3种孔径相同开口孔隙率和渗流面积不同的黏土基微孔陶瓷灌水器,进行了水力性能和土壤入渗试验研究。结果表明,相同条件下微孔陶瓷开口孔隙率和渗流面积越大,灌水器渗流量越大;灌水器入渗性能受灌水时间、土壤类型和进口压力的影响。随着灌水时间延长土壤含水率增加,入渗速率减小;在无压条件下,黄绵土入渗速率较砂土大,随着进口压力增大,砂土入渗速率大于黄绵土入渗速率;同时随着进口压力增大灌水器入渗速率增大且稳定时间缩短。     

微孔陶瓷渗灌与地下滴灌土壤水分运移特性对比

以微孔陶瓷灌水器为研究对象,在0 m工作水头下进行土壤水分运移特性试验,并以10 m额定工作水头下工作的地下滴灌灌水器作为对照。通过对比分析2种灌溉方式下累计入渗量、流量、湿润体特征和土壤含水率变化,结果表明:相同灌溉时间下微孔陶瓷渗灌的累计入渗量、湿润锋运移距离、湿润体截面面积均明显小于地下滴灌。微孔陶瓷渗灌的流量随时间逐渐减小,直至接近于零;试验后期,微孔陶瓷渗灌湿润体内整体土壤含水率变化较小;由于微孔陶瓷渗灌为无压连续灌溉,因此在其工作过程中可为作物提供一个恒定的水分环境。而地下滴灌的流量则会维持稳定,使得土壤含水率一直增大,停止灌溉后由于土壤水分再分布而减小。地下滴灌为被动恒压灌溉,因此其灌溉条件下作物生长的水分环境处于干湿交替的循环变化状态。     

基于HYDRUS-3D模型的微润灌溉土壤水分入渗模拟

掌握土壤水分入渗规律对于合理制定灌溉方案、设置灌溉参数和改进灌溉技术有重要意义。为探究微润灌溉条件下土壤水分入渗规律,利用HYDRUS-3D有限元模型对微润灌溉下土壤水分入渗进行了数值模拟,讨论了初始压力水头和土壤质地对土壤水分入渗的影响。数值模拟结果显示：在土壤水分入渗的垂直剖面上湿润体以微润管为中心呈同心圆状向外扩散,扩散速率与初始压力水头呈正相关。模拟试验周期为36h,分3个时间段进行土壤水分扩散速率的计算,0~5h内土壤水分平均入渗速率为1.85cm/h,6~15h内的平均入渗速率为0.79cm/h,16~36h内的平均水分入渗速率为0.59cm/h。土壤含水率最大值出现在微润管周围,向外围呈减小趋势。相同时间内土壤湿润峰运移距离随初始压力水头的增大而增大,微润灌溉下水分入渗速率在3种质地的土壤（砂壤土、壤土、粘壤土）中依次增大,并测得在压力水头为-180cm时整个模拟周期中3种质地土壤的平均水分扩散速率分别为：0.69、0.53、0.46cm/h。研究表明,土壤含水率和水分扩散速率随压力水头的增大而增大,随土壤黏粒含量的增大而减小。     

膜孔灌土壤湿润体水分分布与入渗特性数值模拟

以非饱和土壤水分运动理论为基础,建立了膜孔灌土壤水分运动的数学模型,并用SWMS-3D软件进行求解,利用室内试验对模拟结果进行分析验证,模拟值与实测值基本吻合,所建模型合理。用所建立的模型和方法对一定灌水技术要素组合下的土壤湿润体水分分布、膜孔入渗量进行数值模拟,结果表明：除膜孔间距大时,膜孔附近土壤水分分布不均匀程度增大外,土壤质地、容积密度、初始含水率、膜孔直径和灌溉水深对膜孔灌土壤水分分布模式影响较小。土壤质地、容积密度对膜孔灌的入渗特性影响显著,土壤初始含水率和灌溉水深对其影响较小。膜孔控制区域内的平均入渗水深主要受开孔率和膜孔直径的影响。     

膜孔灌土壤湿润体水分分布与人渗特性数值模拟

以非饱和土壤水分运动理论为基础,建立了膜孔灌土壤水分运动的数学模型,并用SWMS-3D软件进行求解,利用室内试验对模拟结果进行分析验证,模拟值与实测值基本吻合,所建模型合理.用所建立的模型和方法对一定灌水技术要素组合下的土壤湿润体水分分布、膜孔入渗量进行数值模拟,结果表明:除膜孔间距大时,膜孔附近土壤水分分布不均匀程度增大外,土壤质地、容积密度、初始含水率、膜孔直径和灌溉水深对膜孔灌土壤水分分布模式影响较小.土壤质地、容积密度对膜孔灌的入渗特性影响显著,土壤初始含水率和灌溉水深对其影响较小.膜孔控制区域内的平均入渗水深主要受开孔率和膜孔直径的影响.     

不同泥沙级配浑水灌溉下土壤水分增长特性及成因分析

通过在测坑中开展灌溉条件下2种含沙量4种泥沙级配组合下的浑水灌溉入渗试验,发现泥沙级配对土壤水分增长过程的影响显著:泥沙级配越细,相同灌溉入渗历时的累积入渗量和土壤含水量增加量越小,与清水灌溉试验结果的差异性越大。土壤含水量的增长过程与累积入渗量变化过程均符合指数为正的幂函数关系,说明土壤含水量的增长过程是灌水量在土壤中的分配过程;累积入渗量的变化过程反映了作为整体——测坑土壤含水量的增加过程,某一时刻的累积入渗量是灌溉过程中同时刻不同深度土壤含水量的变化量的叠加。针对泥沙级配作用下土壤水分的增长特性,其成因在于浑水灌溉时土壤表面形成的沉积层,含沙量越大,泥沙级配越细,沉积层越密实,水分通过空隙所受的阻力越大,导致土壤水分增长越缓慢。     

泥沙级配对浑水灌溉下土壤水分增长过程的影响分析

通过在测坑中开展灌溉条件下2种含沙量4种泥沙级配组合下的浑水灌溉入渗试验,发现泥沙级配对土壤水分增长过程的影响显著:泥沙级配越细,相同灌溉入渗历时的累积入渗量和土壤含水量的增加量越小,与清水灌溉试验结果的差异性越大。同一含沙量浑水灌溉,泥沙级配越细,不同深度土壤含水量始变历时和增长拐点历时更长;同一泥沙级配浑水灌溉,含沙量越大,不同深度土壤含水量始变历时和增长拐点历时更长。相同入渗历时,浑水灌溉下的累积入渗量和土壤含水量变化量均较清水灌溉的小,土壤水分增长较清水缓慢;由于浑水中泥沙的阻渗和减渗作用,同一含沙量条件下,泥沙级配越细,灌水后相同入渗历时的土壤含水量变化量和累积入渗量越小;同一泥沙级配浑水,含沙量越大,灌水后相同入渗历时的土壤含水量变化量和累积入渗量越小。     

冬小麦不同深度灌水条件下土壤水分运动数值模拟

冬小麦深度灌水可以促进根系深扎,提高水分利用率。为了定量计算深度灌水条件下土壤水分动态,根据冬小麦不同深度灌水试验,用土壤水分运动方程的源项模拟不同深度灌水,建立了冬小麦不同深度灌水条件下土壤水分运动模型,采用有限差分法求解。利用不同深度灌水冬小麦试验数据对模型进行验证,结果表明模型计算的土壤含水率与实测土壤含水率的动态变化趋势一致,二者显著相关,相关系数在0.90以上,模型平均绝对误差最大值为0.023 cm3/cm3,平均相对误差最大值为8.22%,均方根误差最大值为0.03 cm3/cm3。所建模型具有较高的模拟精度,可用于模拟不同深度灌水条件下冬小麦土壤水分分布与动态变化。     

不同灌水量和灌水器埋深下单坑渗灌红壤水分入渗特性及其模拟

[目的]探究灌水量和灌水器埋深对单坑渗灌红壤水分入渗特性的影响.[方法]通过室内土箱试验模拟大田单坑渗灌过程,研究了单坑渗灌红壤在不同灌水量(1、2L和3L)和不同灌水器埋深(10、15cm和20cm)条件下湿润锋运移距离、累积入渗量和土壤含水率的分布规律,并采用交替方向隐式差分法对土壤水分空间分布进行了模拟.[结果]...     

Overland water and salt flows in a set of rice paddies

Cultivation of paddy rice in semiarid areas of the world faces problems related to water scarcity. This paper aims at characterizing water use in a set of paddies located in the central Ebro basin of Spain using experimentation and computer simulation. A commercial field with six interconnected paddies, with a total area of 5.31 ha, was instrumented to measure discharge and water quality at the inflow and at the runoff outlet. The soil was classified as a Typic Calcixerept, and was characterized by a mild salinity (2.5 dS m⁻¹) and an infiltration rate of 5.8 mm day⁻¹. The evolution of flow depth at all paddies was recorded. Data from the 2002 rice-growing season was elaborated using a mass balance approach to estimate the infiltration rate and the evolution of discharge between paddies. Seasonal crop evapotranspiration, estimated with the surface renewal method, was 731 mm (5.1 mm day⁻¹), very similar to that of other summer cereals grown in the area, like corn. The irrigation input was 1874 mm, deep percolation was 830 mm and surface runoff was 372 mm. Irrigation efficiency was estimated as 41%. The quality of surface runoff water was slightly degraded due to evapoconcentration and to the contact with the soil. During the period 2001–2003, the electrical conductivity of surface runoff water was 54% higher than that of irrigation water. However, the runoff water was suitable for irrigation. A mechanistic mass balance model of inter-paddy water flow permitted to conclude that improvements in irrigation efficiency cannot be easily obtained in the experimental conditions. Since deep percolation losses more than double surface runoff losses, a reduction in irrigation discharge would not have much room for efficiency improvement. Simulations also showed that rice irrigation performance was not negatively affected by the fluctuating inflow hydrograph. These hydrographs are typical of turnouts located at the tail end of tertiary irrigation ditches. In fact, these are the sites where rice has been historically cultivated in the study area, since local soils are often saline-sodic and can only grow paddy rice taking advantage of the low salinity of the irrigation water. The low infiltration rate characteristic of these saline-sodic soils (an experimental value of 3.2 mm day⁻¹ was obtained) combined with a reduced irrigation discharge resulted in a simulated irrigation efficiency of 60%. Paddy rice irrigation efficiency can attain reasonable values in the local saline-sodic soils, where the infiltration rate is clearly smaller than the average daily rice evapotranspiration.     

瓦房店市水果生产标准化发展研究

瓦房店市是我国重要的水果生产基地,在国内水果生产领域占有重要地位。随着水果市场化的不断深入,如何满足和适应国内外市场需求成为瓦房店市水果生产的关键问题。从瓦房店市水果生产实际出发,阐述了实施水果生产标准化的必要性,提出了发展水果生产标准化的具体措施。     

金谷子耐旱TG118引种试种及推广应用

对引进的谷子新品种金谷子耐旱TG118进行品种比较试验和多点试种。结果表明：该品种抗旱、耐瘠、适应性强,稳产、高产、抗病抗风抗倒伏强,品质优良,粮草兼用,种植简单,省工易管;一般产量在6000kg/hm2以上,比当地主栽品种增产20%以上。最高产量达9450kg/hm2,适于在辽西北地区推广应用。     

对《种子法》存在问题的探讨

《种子法》是我国种植业第一部法律。自实施以来,为依法加强种子管理提供了有力的法律支撑,促进我国种子产业发生翻天覆地的变化。但随着依法管理工作的深入和种子产业的快速发展,《种子法》及配套规章的一些问题逐步显现出来。对《种子法》及配套规章存在的问题进行深入分析,对需要进一步补充的章节以及需要调整的内容进行深入探讨,以求更加完善和明确。     

Review of the Egyptian experience in implementing land drainage projects

About 30 years have passed since the Government of Egypt embarked on implementing a series of large scale drainage projects. At present, about 3.8 million acres have been provided with drainage systems on the basis of systematic pre-drainage investigations and designs. The target is to provide drains in approximately 6.4 million acres in the Nile Valley and Delta.The implementation of the subsurface drainage system is carried out by the public sector and private contractors under direct supervision of governmental regional departments. The implementation process depends on many factors related to the drainage material, machinery, manpower, site requirements, farmers and organizations involved. Problems and constraints are sometimes challenging, however, the annual rate of implementation has gradually increased to 170,000 acre/year.This paper discusses the different aspects involved in the implementation process of drainage systems. The development in materials, machinery and construction technologies will be reviewed. Institutional and management factors are going to be also considered.     

和谐社会理论建设的几点哲学思考

在新世纪,面对机遇和挑战,党的十六大把“社会更加和谐”作为全面建设更高水平的小康社会的一个重要目标。中国人素有社会和谐的理想;西方人自古也向往社会和谐;借鉴东西方两种和谐社会思想的经验、教训,构建社会主义和谐社会理论。     

A European irrigation map for spatially distributed agricultural modelling

We present a pan-European irrigation map based on regional European statistics, a European land use map and a global irrigation map. The map provides spatial information on the distribution of irrigated areas per crop type which allows determining irrigated areas at the level of spatial modelling units. The map is a requirement for a European scale assessment of the impacts of irrigated agriculture on water resources based on spatially distributed modelling of crop growth and water balance. The irrigation map was compiled in a two step procedure. First, irrigated areas were distributed to potentially irrigated crops at a regional level (European statistical regions NUTS3), combining Farm Structure Survey (FSS) data on irrigated area, crop-specific irrigated area for crops whenever available, and total crop area. Second, crop-specific irrigated area was distributed within each statistical region based on the crop distribution given in our land use map. A global map of irrigated areas with a 5′ resolution was used to further constrain the distribution within each NUTS3 based on the density of irrigated areas. The constrained distribution of irrigated areas as taken from statistics to a high resolution dataset enables us to estimate irrigated areas for various spatial entities, including administrative, natural and artificial units, providing a reasonable input scenario for large-scale distributed modelling applications. The dataset bridges a gap between global datasets and detailed regional data on the distribution of irrigated areas and provides information for various assessments and modelling applications.     

粉质仪和拉伸仪在面粉生产中的应用

在介绍粉质仪和拉伸仪结构和原理的基础上,探讨了粉质曲线中吸水率、形成时间、稳定时间、弱化度和评价值等指标与面粉品质的关系,以及如何根据拉伸曲线中面团最大拉伸阻力、延伸度和拉伸曲线面积等指标来评价面团品质,并结合生产实际,概述了粉质仪和拉伸仪在面粉生产中的作用。     

农村信息化服务的现状及建设措施

分析当前我国农村信息化服务的现状,提出加强农村信息化服务的新举措。     

车辆ABS控制算法的研究及探讨

对现代汽车的ABS控制算法作了一些简单的介绍,同时指出了它们的一些缺陷,相应地提出了几种对ABS的其它控制方法并加以探讨,其中着重论述了ABS门限值控制算法中参考车速的确定方法和基于附着系数的控制算法。