Time-variable soil hydraulic properties in near-surface soil water simulations for different tillage methods

Simulating near-surface soil water dynamics is challenging since this soil compartment is temporally highly dynamic as response to climate and crop growth. For accurate simulations the soil hydraulic properties have to be properly known. Although there is evidence that these properties are subject to temporal changes, they are set constant over time in most simulations studies. The objective of this study was to improve near-surface soil water simulations by accounting for time-variable hydraulic properties. Repeated tension infiltrometer measurements over two consecutive seasons were used to inversely estimate the hydraulic properties of a silt loam soil under different tillage - conventional (CT), reduced (RT), and no-tillage (NT). Simulated water dynamics with constant and time-variable hydraulic parameters were compared to observed data in terms of the soil water content and water storage in the near-surface soil profile (0-30 cm). The measurements indicate a considerable temporal variability in the saturated hydraulic conductivity, the field-saturated water content and the parameter α of the van Genuchten/Mualem model. Temporal variability was largest for CT and RT, whereas under NT, replicates of measured water contents and hydraulic properties showed a considerable large spatial variability. Simulations with time-constant hydraulic parameters led to underestimations of soil water dynamics in winter and early spring and overestimations during late spring and summer. The use of time-variable hydraulic parameters significantly improved simulation performance for all treatments, resulting in average relative errors below 13%. Since simulation results agreed with observed water dynamics in two seasons, the applicability of inversely estimated hydraulic properties for soil water simulations is demonstrated. Thus, simulations that address applied questions in agricultural water management may be improved by using time-variable hydraulic parameters. The simulated water balance indicated that RT and NT result in better water storage than CT and therefore may increase water efficiency under water-limited climatic conditions.     

植被群落演替对土壤饱和导水率的影响

土壤饱和导水率是表征土壤入渗能力的重要参数,对不同土地利用类型反应敏感。为了揭示植被演替对土壤剖面上饱和导水率的影响规律,采用恒定水头法测定了天童林区155 a植物群落演替序列60 cm深土壤剖面上的饱和导水率。结果表明,不同演替阶段饱和导水率均随土壤深度增加迅速降低,在0～20 cm土层内,各演替阶段饱和导水率均存在极显著差异,0～60 cm土层内饱和导水率的平均值从裸地、石栎+檵木灌丛、马尾松林、木荷+马尾松林、木荷林到栲树林升高极为显著,植物群落演替到灌丛阶段,平均饱和导水率已与裸地存在显著差异,演     

不同离子微咸水对土壤水力特性和生菜生长的影响

为探究不同微咸水水质对土壤水力特性和作物生长的影响,在日光温室条件下,以生菜为供试作物开展2季盆栽试验.以CaSO₄的饱和溶液为对照(CK),向去离子水中添加不同氯化盐形成电导率相同而阳离子组成不同的微咸水处理(分别为Na⁺∶T_Na;Na⁺/K⁺比为1∶1:T_Na-K;K⁺∶T_K),研究连续灌溉下土壤容重、持水性能、水盐运移,以及生菜生长响应,并采用van Genuchten模型对水分特征曲线相关参数进行拟合分析.结果表明:与CK相比,微咸水灌溉均增加了土壤容重,降低了土壤孔隙度;随着微咸水持续灌溉,土壤孔隙分布明显改变,微小孔隙比例增加,土壤持水能力显著提高,以处理T_Na最为显著.连续微咸水灌溉下,灌溉水钠吸附比、土壤结构稳定性阳离子比与土壤进气值参数存在负相关关系(R²均为0.78).土壤中盐分逐渐积累,表现为第2季生菜生长季末(播后80 d)各处理0~20 cm土壤饱和提取液电导率较第1季显著升高,其中CK显著低于其他处理(P<0.05),且表层土壤(0~10 cm)中盐分积累更为明显.生长季末土壤表层含水量较高,与盐分分布基本一致.与CK相比,处理T_Na,T_Na-K和T_K显著降低了生菜生物量的积累(P<0.05),其中T_Na最低.     

Effect of tillage and water table control on evapotranspiration,surface runoff,tile drainage and soil water content under maize on a clay loam soil

Two tillage and two water table control treatments under continuous maize cropping were evaluated over a 3-year period (1992–1994) for their effects on evapotranspiration, surface runoff (SR), tile drainage (TD) and soil water content in the root-zone on a clay loam soil in southern Ontario. The tillage treatments included soil saver (SS, reduced tillage) and moldboard plow (MP, conventional tillage). The water table control treatments included controlled drainage-subirrigation (CDS) and regular tile drainage (DR). There was no significant difference (P<0.05) in evapotranspiration estimates between the SS and MP tillage treatments. The SS tillage increased SR compared with MP tillage during the non-cropping periods in 1993 and 1994, but not in 1992. Relative to MP, the SS tillage increased soil profile water content during the cropping period but decreased soil profile water content during the non-cropping period in 1992. The CDS treatment produced significantly higher (P<0.05) evapotranspiration and soil water content than the drainage treatment during the dry 1993 and 1994 years, but not during the wet 1992 year. The CDS treatment also had significantly lower (P<0.05) TD and higher SR than the drainage treatment. For all the treatments, over 65% of SR and TD occurred in the 5 month non-cropping period from November to March. Of the total annual water input (precipitation and/or subirrigation) to the field site, 8% was partitioned to SR, 30% was partitioned to TD, 55% was removed by crop and soil evapotranspiration and 7% was accounted for by changes in soil profile water content.     

生物结皮对土壤水气传输特性的影响

为研究生物结皮对土壤气体传输、水力传导特性的影响,在陕北水蚀风蚀交错区,以4种处理土样(无结皮、去结皮、3 a生结皮和7 a生结皮)为研究对象,进行土壤导气率、饱和导水率和入渗速率的测定分析.结果表明:在土壤吸湿和脱湿过程中,相同土壤含水率所对应的土壤导气率值不同,且脱湿过程的导气率值高于吸湿过程;生物结皮导致土壤导气率降低;由于生物结皮的存在,土壤总孔隙度和毛管孔隙度增加,在增强土壤持水性的同时降低了土壤的导水性;生物结皮生长年限越久,土壤水分入渗的能力显著降低;3种入渗模型中Horton模型的决定系数R²的值大于同处理下其他模型,该模型更适合于用来模拟该区域生物结皮覆盖下的土壤入渗特征.     

Effect of temporal variability in soil hydraulic properties on simulated water transfer under high-frequency drip irrigation

The effect of changes in the hydraulic properties of a loamy topsoil on water transfer under daily drip irrigation was studied over a cropping cycle. Soil water contents were measured continuously with neutron probes and capacitance sensors placed in access tubes (EnviroSMART) and were compared to predications made by the Hydrus-2D model. Three different sets of hydraulic parameters measured before and after irrigation started, were used.Our results demonstrated that, based on the assumptions used in this study, the accuracy of the Hydrus predictions is good. Graphical and statistical comparisons of simulated and measured soil water contents and consequently the total water storage revealed a similar trend throughout the monitoring period for the all three different sets of parameters. The soil hydraulic properties determined after irrigation started were found to be much more representative of the majority of the irrigation season, as confirmed by the accuracy of the simulation results with high values of the index of agreement and with values of RMSE similar in magnitude to the error associated with field measurements (0.020 cm³ cm⁻³). The highest RMSE values (about 0.04 cm³ cm⁻³) were found when the model used input soil parameters measured before irrigation started.Generally, changes in topsoil hydraulic properties over time had no significant effect on soil moisture distribution in our agro-pedo-climatic context. One possible explanation is that daily water application was conducted at the same time as maximal root water uptake. This meant the soil did not need to store total daily crop water requirements and consequently that the water redistribution phase represented a very short stage in the irrigation cycle. It is probable that irrigating in the daytime when crop evapotranspiration is highest could prevent the effects of a temporal change and other problems connected with the soil. Moreover, water will be always available for the crop. Further experiments are needed to justify the results and to study the effects of low frequency drip irrigation on soil hydraulic characterization and consequently on soil water transfer in order to improve irrigation scheduling practices.     

Evaluation of the parameters involved in Gardner's relation between unsaturated hydraulic conductivity and soil water matric suction

An experimental study on evaporation from homogeneous sandy and loamy soils was carried out to define the unsaturated hydraulic conductivity function. Gardner's empirical function k(ψ) (1958) was used in the analysis of experimental data. Parameters involved in the k(ψ) functions obtained were evaluated. The error due to exclusion of the b-factor varied with the depth of water table for both sandy and loamy soils.     

Modeling soil water dynamics in a drip-irrigated intercropping field under plastic mulch

Intercropping, drip irrigation, and the use of plastic mulch are important management practices, which can, when utilized simultaneously, increase crop production and save irrigation water. Investigating soil water dynamics in the root zone of the intercropping field under such conditions is essential in order to understand the combined effects of these practices and to promote their wider use. However, not much work has been done to investigate soil water dynamics in the root zone of drip-irrigated, strip intercropping fields under plastic mulch. Three field experiments with different irrigation treatments (high T1, moderate T2, and low T3) were conducted to evaluate soil water contents (SWC) at different locations, for different irrigation treatments, and with respect to dripper lines and plants (corn and tomatoes). Experimental data were then used to calibrate the HYDRUS (2D/3D) model. Comparison between experimental data and model simulations showed that HYDRUS (2D/3D) described different irrigation events and SWC in the root zone well, with average relative errors of 10.8, 9.5, and 11.6 % for irrigation treatments T1, T2, and T3, respectively, and with corresponding root mean square errors of 0.043, 0.035, and 0.040 cm³ cm^?3, respectively. The results showed that the SWC in the shallow root zone (0–40 cm) was lower under non-mulched locations than under mulched locations, irrespective of the irrigation treatment, while no significant differences in the SWC were observed in the deeper root zone (40–100 cm). The SWC in the shallow root zone was significantly higher for the high irrigation treatment (T1) than for the low irrigation treatment, while, again, no differences were observed in the deeper root zone. Simulations of two-dimensional SWC distributions revealed that the low irrigation treatment (T3) produced serious severe water stress (with SWCs near the wilting point) in the 30–40 cm part of the root zone, and that using separate drip emitter lines for each crop is well suited for producing the optimal soil water distribution pattern in the root zone of the intercropping field. The results of this study can be very useful in designing an optimal irrigation plan for intercropped fields.     

Components of the water balance in soil with sugarcane crops

The objective of this study was to analyze the components of the water balance in an Ultisol, located in the municipality of Jaboticabal, SP, Brazil (21°20′20″S, 48°18′35″W), that was cultivated with sugarcane. The monitoring was performed during the agricultural cycle of the first ratoon between 11/16/2006 and 7/9/2007. Three treatments were established in four blocks with doses of ammonium sulfate, as follows: Treatment 1 (T₁), without fertilizer; Treatment 2 (T₂), 100 kg ha⁻¹ of nitrogen (N) and 114 kg ha⁻¹ of sulfur (S); and Treatment 3 (T₃), 150 kg ha⁻¹ of N and 172 kg ha⁻¹ of S. Rainy precipitation (P) in the area was measured with a rain gauge. The soil water storage (H) and the soil water storage variations (ΔH) were determined by the gravimetric method, and the internal drainage (D)/capillary rise (CR) at a depth of 0.9 m was quantified by the water flux density using the Darcy–Buckingham equation. The actual evapotranspiration (ET_a) was calculated as follows: ET_a = P − D + CR ± ΔH. During the study period, the amount of rainfall was 1406 mm, 121 mm greater than the historic average for the region (1285 mm), with a notable peak in the month of January of 402 mm (historic average: 251 mm). The internal drainage was 300 mm under T₁, 352 mm under T₂, and 199 mm under T₃, and this was relevant during times with elevated P, when the actual H was greater than the field capacity H. The actual evapotranspiration (T₁: −897.7 mm, T₂: −847.5 mm, and T₃: −970.8 mm) and the water use efficiency (T₁: −131.3 kg mm⁻¹, T₂: −146.6 kg mm⁻¹, and T₃: −127.5 kg mm⁻¹) did not differ among the treatments. The dispersion of D was greater than the other components of the water balance, especially during the period of elevated P, with the errors of this process propagated in the estimation of ET_a. Despite of this propagated standard deviation of ET_a, it accounted less than 15% of the total ET_a, showing that the method may be conveniently used in field studies with sugarcane crops.     

The effect of microorganisms,salinity and turbidity on hydraulic conductivity of irrigation channel soil

The introduction of polysaccharide producing benthic algae and bacteria could provide a low cost technique for seepage control in irrigation channels. The ability of algae and bacteria to produce polysaccharides proved to be successful in reducing the hydraulic conductivity of irrigation channel soil. Hydraulic conductivity was reduced to less than 22% of its original value within a month of inoculating soil columns with algae. Chlorophyll and polysaccharide concentrations in irrigation channel soil were measured in order to assess the growth of algae and extent of polysaccharide production, and their correlation with hydraulic conductivity of channel soil. Increases in polysaccharide occurred in the top layer (0–5 mm) of the soil column. The reduction of hydraulic conductivity was highly correlated with the amount of polysaccharides produced (r ² = 0.92). Hydraulic conductivity decreased with increasing algal and bacterial numbers. The first few millimetres of the soil core where microbial activity was concentrated, seemed effective in controlling seepage. Incorporation of extra nitrate and phosphate into algal medium did not increase the production of polysaccharides by algae in channel soil. The effect of salinity and turbidity of irrigation channel water on channel seepage was studied by measuring the effects on hydraulic conductivity of channel soils. When the electrical conductivity (EC) of the water increased above a threshold value, the hydraulic conductivity increased because of the flocculating effects on clay particles in channel soils. A relationship between sodium adsorption ratio (SAR) and EC of the channel water was established which indicated 15% increase in channel seepage due to increases in salinity. Increasing the turbidity of irrigation water (by increasing the concentration of dispersed clay) resulted in lowering the hydraulic conductivity of the channel soil due to the sealing of soil pores by dispersed clay particles. When the turbidity of the water was 10 g clay l^–1, the hydraulic conductivity was reduced by 100%. An increase in clay concentration above 1 g l^–1 resulted in significant reduction in hydraulic conductivity. Soil bowl experiments indicated that clay sealing with a coating of hydrophobic polymer on the surface could also effectively prevent seepage of saline water.     

基于HYDRUS对稻田不同阶段土壤水分的模拟与分析

为探寻稻田不同阶段土壤水分状况下的差异性,基于重庆丘陵区紫色土常规轮作水稻土壤水分的连续监测数据,利用HYDRUS-1D模型对稻田淹水、排水落干和收获后3个不同干湿阶段(阶段Ⅰ,Ⅱ,Ⅲ)的土壤水力参数和土壤含水量开展验证模拟分析.研究表明：(1)根据R²与RMSE的误差分析结果,HYDRUS可以实现对不同阶段稻田土壤水分变化的有效模拟.(2)根据土壤水量平衡分析,阶段Ⅰ的稻田土壤水分以水分补充的形式为主;阶段Ⅱ和Ⅲ的土壤水分以水分损失为主,底层渗漏量分别占总水分损失量的52%和95%.(3)根据HYDRUS的模拟结果,降雨直接影响土壤上下边界流的变化;阶段Ⅱ的实际作物蒸腾量和实际地表蒸发量低于阶段Ⅰ的,阶段Ⅲ稻田土壤的地表实际蒸发量与日照时数的关系更密切.     

不同耕作方式对植烟土壤团聚体分布及稳定性的影响*

为探究植烟土壤团聚体分布及稳定性对不同耕作方式的响应,以丘陵烟区烟田黄壤土为研究对象,通过田间定位试验,设置深松1遍(T1)、常规旋耕2遍(T2)和翻耕1遍+旋耕1遍(T3)3个处理,研究不同耕作方式对植烟土壤团聚体分布及稳定性的影响,包括对力稳定性团聚体含量、水稳定性团聚体含量、团聚体平均重量直径、水稳性团聚体稳定率、构体破碎率和不稳定团粒指数进行测定与分析。结果表明：与翻耕1遍+旋耕1遍处理相比,深松1遍和旋耕2遍处理可使0~20cm土壤层的0.25-2mm粒级团聚体的力稳性团聚体数量显著提高,20~30cm土壤层的＞0.25mm粒级团聚体的力稳性团聚体数量显著提高。深松1遍和旋耕2遍处理可使0~10cm和20~30cm土壤层的平均重量直径(干筛)值和0~30cm土壤层的平均重量直径(湿筛)值显著提高。深松1遍处理可使0~10cm土壤层的水稳性团聚体稳定率增大,而旋耕2遍处理可使10~20cm和20~30cm土壤层的水稳性团聚体稳定率增大。上述研究结果说明,采用适宜的耕作方式将有助于植烟土壤团聚体形成和稳定性的提升,为优化丘陵烟区耕作方式提供理论支撑。     

Effects of soil tillage and fallow management on soil water storage and sunflower production in a semi-arid Mediterranean climate

Normally sown in March in the region of Meknès (Morocco), rainfed sunflower suffers from a severe water deficit from anthesis which seriously affects grain filling. Increasing the stored soil water by appropriate management during the long period of bare soil preceding sunflower planting could be an opportunity which has not been explored for this spring-sown crop.Five methods for autumn soil tillage (mouldboard ploughing, chiselling, paraploughing, disc harrowing, no tillage) and four fallowing methods (chemical weed control, mechanical weeding, allowing weeds and volunteer crops, sowing barley) were compared in Meknès between 1994 and 1998 on calcimagnesic soils with vertic behaviour. Two additional experiments were carried out in 1997 and 1998 to create a range of leaf area indexes and transpiration requirements for sunflower. This was obtained (i) in 1997, by four levels of plant density (2.5–10.0 plants/m²) and three levels of soil water at planting (89, 37, and 29% of total available soil water); (ii) in 1998, by six levels of sunflower defoliation at star bud stage. Simulations with the EPIC-Phase model were performed to explore a wider range of weather conditions (1960–1998) than experienced.The differences in water storage at planting were explained partly by the mode of action of each of the implements tested and partly by the weather conditions which prevailed during the fallow period. After a very dry fallow period (with a frequency less than 1 year in 10), water storage was maximal after disc harrowing and paraploughing (including straw mulching) because soil layers were only marginally exposed to evaporation. Conversely, in a year with a wet fallow period (with a frequency of 4 years in 10), mouldboard and chisel ploughing gave the largest water reserves at planting because of better infiltration at depth with increased porosity. When the fallow period was initially wet, but dry in early spring (with a frequency of 2 years in 10), minimum and no tillage gave the best water storage but the differences between tillage methods were small. In spite of differences in soil water content at planting and clear differences in rooting systems, sunflower yield and seasonal water use were not significantly affected by soil tillage provided that the plant population was the same and weed control was adequate in reduced tillage systems. However, chisel ploughing was a good compromise for maximising stored water at sunflower planting on the clay soils of Meknès.Surprisingly, maximizing soil water content at sunflower planting was not systematically the best solution for maximizing sunflower yield and water use efficiency under the semi-arid conditions of Meknès. A high soil water content at planting leads to excessive leaf area index at the bud stage and consequently to rapid water depletion and yield reduction, especially when seasonal precipitation is low. A 50% refilling of the soil water reserve is sufficient for spring-sown sunflower as was confirmed by the simulation study. Soil moisture in the uppermost layer which governs seedling establishment is a more limiting factor for sunflower yield than total soil water content at planting.     

水利工程设计中水土保持理念辨析

我国地质地貌多种多样,水土流失时有发生,对我国经济发展和人民的生活都带来了较大影响.在水利工程建设中,对环境的影响一般就是水土流失,这种现象并不少见,需要我们引起重视.施工方案要科学,要对水土资源起到保护的作用,以此来减少水土流失的发生.基于水利工程设计中水土保持理念,为了防止出现这样的问题,提出了相应的改进水土保持方案的具体措施,希望能够减少水利工程建设中水土流失现象的发生.     

不同灌溉制度对根层土壤盐分影响的模拟

以河套灌区沙壕渠灌域为例,采用SaltMod模型探讨了不同灌溉制度对作物根层土壤盐分的影响.利用2008-2010年基础资料对模型进行率定和验证并对研究区的根层土壤盐分进行模拟和预测.结果表明:在现有灌排条件下,沙壕渠灌域的盐渍化程度基本达到较为稳定的水平,且有轻微脱盐趋势,未来10 a后作物根层土壤盐分降低3%.生育期土壤水盐垂直交换运动强烈,对于控制土壤盐分而言,灌水量越小越好;作物根层土壤盐分随冬灌灌溉定额的增大而减小,不同冬灌灌溉定额对应的根层土壤盐分最初的增加量均较大,但增加的趋势随时间逐渐降低.根据当地作物种植结构,综合考虑节水灌溉、作物产量和根层土壤水盐环境,建议研究区较优的作物生育期综合净灌溉定额为2 700~3 500 m³/hm²,冬灌净灌溉定额为2 700 m³/hm².     

Effect of variations in soil properties and precipitation on microcatchment water balance

The objective of the study was to investigate the effect of combined variabilities of rain and soil parameters as stochastic inputs for a runoff model on a microcatchment area of 250 m². This area was assumed to be a water harvesting element for a single almond tree and simulated a microcatchment water harvesting project in the Negev Desert of Israel. The average annual precipitation is about 120 mm. This can be described in terms of the number of storms per year, intensity and duration. In a 20-year simulation, the number of storms per year varied from 1 to 22. Annual rainfall ranged from 15 and 310 mm, and was strongly dependent upon the number of storms. The runoff from twenty microcatchment elements was calculated and used to predict the yield of water and almonds. Results indicated that the runoff probability density is strongly skewed toward the low values and is log-normally distributed for the time-space combinations. Twenty-five percent of the time a plot failed to yield the annual runoff required to produce a commercial almond yield. The average yield of almonds was reduced below the optimal relationship. However, results from the simulation indicate that planting the trees in clusters rather than a single tree per microcatchment element may be a way to address this problem.     

Changes in hydraulic conductivity of soils varying in calcite content under cycles of irrigation with saline-sodic and simulated rain water

Soil infiltration problems occur as a result of alternating irrigation with saline-sodic waters and monsoon rainfall. Hydraulic conductivity (K) and related soil properties of a non-calcareous (CaCO₃ 0.8%) and a calcareous soil (25.7%) having similar textural constituents were monitored. The soils were subjected to six consecutive cycles of irrigation with saline waters (SW) of sodium adsorption ratio (SAR), 10, 20 or 30 (mmol/l)^1/2, but of similar electrolyte concentration (EC; 80 mEq/l), and each followed by simulated rain water (SRW) (electrical conductivity <0.02 dS/m). Results are presented in terms of relative K i.e. K _r=K _sw/K _tw where K _tw is steady state K measured separately under application with tap water (ECw 0.54 dS/m, SAR 0.9). For irrigation with SW alone, K _r values were reduced to 0.95, 0.79 and 0.70 at SAR of 10, 20 and 30, respectively, in non-calcareous soil. The corresponding values of 0.95, 0.87 and 0.79 were slightly higher in calcareous soil. Severe reductions in K _r were observed in both the soils when subjected to alternate use of SW and SRW (K _r=0.22, 0.03 and 0.02 in non-calcareous, and 0.57, 0.17 and 0.07 in calcareous soil). About half of the reductions in K _r were reversible when SW was subsequently applied. Depth distributions of salinity, pH, dispersible clay and hydraulic head indicate that disaggregation and dispersion of surface soil was the cause of reduced K with SRW, whereas “washed in” sub-soil became restrictive and controlled the K values with SW under alternations of SW and SRW. Salt release (<1 mEq/l) was insufficient to avoid dispersion and sustain K even in the calcareous soil. For evaluating the infiltration hazard of saline-sodic water, measurements of stabilized K values after consecutive cycles of SW and SRW should serve as a better diagnostic criteria under monsoonal climates than threshold EC–SAR combinations. Received: 8 June 1998     

基于水量平衡下的灌区用水计划编制方法综述

为了精准指导农田灌溉,合理优化渠系输配水,提高水资源的利用率、灌区的管理水平和总效益,对灌区用水计划的编制方法展开了理论研究.将用水计划的编制过程概括为实时灌溉预报和渠系配水两部分,分别进行归纳整理和分析.在对国内灌区用水计划的编制方式进行了解的基础上,着重介绍了利用土壤水分平衡方程进行实时灌溉预报的方法,总结各参数预测值和计算修正值的获取方法,分析对比各方法的适用范围,提炼普遍灌区实时灌溉预报中适用的方法.为了优化田间渠系配水次序和配水量,以保证作物得到及时有效灌溉,归纳总结了国内灌区常用的渠系配水模型,论述了常见的目标函数及相关约束的选取原则,并指出其局限性和可能的发展趋势.研究结果可为各灌区进行实时灌溉预报和建立优化配水模型提供借鉴与参考.     

基于HYDRUS-3D的涌泉根灌土壤入渗数值模拟

针对涌泉根灌流量大且出流边界为柱状,与传统滴灌、渗灌等存在很大差异的问题,依据非饱和土壤水动力学理论,并结合涌泉根灌条件下土壤水分运动特征,建立了具有柱状出流边界的入渗模型,利用HYDRUS-3D对模型进行求解,所建模型通过土壤剖面含水率随时间变化的实测值与模拟值的对比进行验证.结果表明:模拟值与实测值的相对误差在10％以内,两者具有较好的一致性,数值模拟结果可为涌泉根灌系统的合理设计及运行提供理论依据.通过数值模拟方法研究了流量、套管开孔长度对土壤含水率的影响,发现流量越大,水分运移速率越大,随着时间推移流量所引起的差异减小;灌水量相同时,灌水结束后土壤湿润体范围随流量增大略有减小;开孔区长度增加对湿润体形状、大小没有显著影响,但对土壤湿润体内水分分布状况影响较大.