共查询到20条相似文献，搜索用时 31 毫秒
1.
A MODEL FOR PREDICTING THE REDISTRIBUTION OF SALTS APPLIED TO FALLOW SOILS AFTER EXCESS RAINFALL OR EVAPORATION 总被引：1，自引：0，他引：1
I. G. BURNS 《European Journal of Soil Science》1974,25(2):165-178
A model is described for predicting the movement of soluble unadsorbed anions (such as nitrate or chloride) in fallow freely drained soil under field conditions. The model includes routines for estimating both the downward leaching of salts (after excess rainfall or irrigation) and the capillary movement of anions to the soil surface (after evaporation). The profile is divided into layers each of which is characterized by a maximum and minimum water content (the field capacity and evaporation limit respectively). Daily amounts of rainfall and evaporation are applied to the surface and the redistribution of water and salts is calculated (on a layer-to-layer basis) from the initial water and salt contents of each layer by adding or subtracting water to or from the moisture content until the stated maximum or minimum value is reached. Salt transfer is calculated from the amount af water movement on a proportional basis. The predictions of the model have been tested using field data for the redistribution of nitrate and chloride in a sandy loam soil. Good agreement was obtained for chloride, but the results for nitrate showed some deviations probably due to the effects of denitrification. 相似文献
2.
Modelling water and solute transport in macroporous soil. I. Model description and sensitivity analysis 总被引：6，自引：0，他引：6
A detailed mechanistic model of water movement and transport of non-reactive solute in a macroporous soil is described. One important feature of the model is that it may be run in either one or two flow domains using the same values for the hydraulic properties characterizing the soil. Water and solute movement in the micropores is calculated with the Richards and convection-dispersion equations and, in two domains, this is coupled to fluxes of water and solute in the macropores by empirical interaction terms. These interaction terms are redundant in the one-domain model, which simply reduces to the non-steady state convection-dispersion equation. A sensitivity analysis is presented showing how it is possible to identify conditions under which a macropore flow domain may need to be considered. In part II (Jarvis et al., 1991), the model is evaluated under field conditions in chloride breakthrough experiments in soil monolith lysimeters. 相似文献
3.
THE ASYMMETRIC LEACHING PATTERN OF NITRATE AND CHLORIDE IN A LOAMY SAND UNDER FIELD CONDITIONS 总被引：1，自引：0，他引：1
In a field experiment on a weakly structured, almost stone-free loamy sand, the depths of leaching of chloride and nitrate were measured after sprinkler irrigation at 8 mm/h. The modal depth of movement of the two ions was about half the mean depth of movement, indicating a highly skewed distribution and a pronounced leading tail of chloride and nitrate. The marked asymmetry of the salt distribution is attributed to uneven downward movement of water, including movement down earthworm channels, which results in part of the nitrate and chloride being deeply leached. 相似文献
4.
The analytical equation of Rose was more successful than the models of Burns and Addiscott in predicting movement of chloride through a soil on Upper Chalk under irrigation and winter rainfall. The two models required water inputs to be divided into 5 mm increments. When this was done the model of Addiscott was more successful than that of Burns although both then gave predictions of acceptable accuracy for practical purposes. The analytical equation of Rose requires a value for solute dispersivity. This was obtained from the experimental measurements, but the value used (3 cm) was found not to be critical. 相似文献
5.
6.
Two models of solute leaching to a mole-pipe drainage system are described. The first model is research-oriented. It simplifies two-dimensional water and solute flow to a mole drain by dividing the soil between the mid-mole plane and the mole into notional compartments. Solute movement between compartments is assumed to occur by convection and mechanical dispersion. Within each compartment a mobile and immobile solute phase is defined, with diffusion occurring between them. Rainfall intensity (over approximately hourly intervals) and basic soil hydraulic data are needed as inputs. An explicit finite-difference solution to the water and solute mass-balance and flux equations is used. The second simpler model is management-oriented. It uses daily time steps, and assumes the soil solution behaves as if it were well-mixed system. It requires only daily rainfall and evaporation data, the drainage coefficient of the mole-pipe system, and the soil macroporosity as inputs. In both models a source/sink term accounts for additions of solute in rainfall and fertilizer, and extraction by plant uptake. The models were used to simulate leaching losses of chloride to a mole-pipe drainage system in a silt loam under pasture, following the application of potassium chloride to the soil surface. The first model simulated leaching better immediately after ertilizer application, and during bypass flow induced by heavy rain. However, both models were able to simulate the measured losses over a 2-year period equally well. 相似文献
7.
8.
浅地下水埋深条件下土壤水盐动态BP网络模型研究 总被引：12，自引：5，他引：7
针对浅地下水埋深条件下作物生育期内根系层土壤水盐动态模拟中存在的问题,将人工神经网络引入水盐动态的模拟和预报中,建立了根系活动层0～60 cm和0～100 cm深度内土壤水盐动态的BP网络模型。结果表明,以生育时段初平均土壤含水率、平均土壤盐分指标、地下水水位埋深、地下水盐分指标、时段内水面蒸发量、降雨量(包括灌水量)、生育期日序列7个因素为输入因子,以生育时段末平均土壤水分、平均土壤盐分指标为输出因子的BP网络模型可有效表征土壤水盐动态及其影响因素之间的内在复杂关系,并且有较高的精度。该研究为分析浅地下水埋深条件下作物生育期内土壤水盐动态规律的分析提供了一种有效可行的方法,是对传统土壤水盐动态研究的补充。 相似文献
9.
Simulation models are useful tools to understand the interaction between the transformation and the transport of nitrogen in the field. This study was done to calibrate, test and analyse a mechanistic, one‐dimensional model that describes the transport and transformations of nitrogen in the soil. The physical module describes transport of water, heat and solute, and the biological module simulates transformations of C and N with a restricted number of measurable organic pools. The calibration was based mainly on laboratory experiments independent of those used to evaluate the model. The evaluation procedure used field data collected on a bare loamy soil. The profiles of water content, water potential, temperature, chloride and nitrate (15N‐labelled and unlabelled) concentrations were measured from 0 to 150 cm continuously for 1 year. Simulated results were in good agreement with experimental data. However, some discrepancies were noticeable for chloride and nitrate concentrations in the deep layers. These differences were probably due to an underestimation of mass transport in the deep layers. A sensitivity analysis was carried out to determine the response to changes in some parameters in terms of mineralization, leaching and model efficiency. Mineralization is more sensitive to biological factors whereas nitrate leaching is more sensitive to initial and boundary conditions and hydraulic parameters. The experiment ran for only 1 year, which was too short a time to test biological factors. 相似文献
10.
Simulating the impact of irrigation management on the water and salt balance in drained marsh soils (Marismas, Spain) 总被引：2，自引：0，他引：2
Abstract. Using the simulation model MACRO, this paper investigates the likely consequences of reduced irrigation inputs on the water and salt balance and crop growth in a drained, saline clay in a Mediterranean climate (Marismas, SW Spain). The model was first successfully validated against field measurements of the soil water and chloride balance, water table depths and drain outflows in the 1989 growing season. Three-year simulations were then performed assuming two different irrigation applications (60 and 75% reductions from the 1989 amount) and two different frequencies (12 or 6 irrigations per growing season). The model predictions suggested that reduced irrigation may lead to up to a 15%) increase in the chloride content of the soil profile after 3 years. Also, despite overall reductions in water discharge, slight increases in chloride leaching via field drains ( c. 4 to 8%) were predicted. The model demonstrated that encroachment of salt into the soil profile may he exacerbated by the non-equilibrium nature of water flow and solute transport ('by-passing flow') in structured clays. With reduced water supply for irrigation, more frequent applications may give marginally better crop yields for the same quantity of irrigation but at the expense of slightly increasing salt concentration in the root zone. 相似文献
11.
利用两区和两流区模型模拟氯离子在黑垆土中的迁移过程 总被引：1，自引：0，他引：1
以原状长武黑垆土为研究对象,针对不同输入方式、不同孔隙水流速条件下的氯离子溶质迁移过程,分析原状土壤中大孔隙存在条件下溶质迁移的特征,对两区模型和两流区模型的各拟合参数进行对比和分析。结果表明:大小脉冲输入条件下,氯离子浓度在试验土柱中均随穿透试验的进行呈现先增加而后降低的趋势,其峰值大小及其出现位置随孔隙水流速变化差异显著,且小脉冲输入时溶质穿透曲线较大脉冲时的不对称和拖尾现象更为显著;两流区模型相对于两区模型可较好描述氯离子的穿透曲线;两模型所得模拟参数随孔隙水流速的变化差异性较大。两模型拟合所得弥散度(λ)随孔隙水流速的变化趋势相同,但两流区模型拟合的弥散度大两区模型拟合值2个数量级。两模型拟合所得可动水含量(β)均随孔隙水流速的增加相应增加,而质量交换系数(α)值均极小。 相似文献
12.
基于GIS的土壤水分运动模型 总被引：1，自引：0，他引：1
我国北方灌溉农田区土壤水分空间差异较大,一维水分模型无法计算土壤水分的空间分布,本研究在V isualBasic环境下结合ArcOb jects控件技术,利用ArcG IS的空间分析能力,开发出一个基于G IS的三维区域土壤水运动模型。该模型以R ichards方程和Van Genuchten公式为基础,通过简单的数据输入及参数设定便能快速的计算出土壤含水量、土壤导水率和土壤水势,对土壤水分空间运动进行模拟,并分别利用参考文献数据及实测数据对模型进行验证,证明计算结果可靠。 相似文献
13.
《Communications in Soil Science and Plant Analysis》2012,43(11):1700-1707
Methodologies that use electromagnetic induction and resistivity in soil profiles to estimate drainage across whole fields and catchments require complex models or measurement systems that are not easily available or difficult to apply at the farm level. The objective of the present study was to define a methodology that could use information easily available to agronomists and commercial cotton consultants to estimate drainage in irrigated Vertisols using a chloride (Cl?) mass balance approach. A secondary objective of this study was to eliminate or minimize the expensive and tedious laboratory analyses for determining Cl? concentration in soils. A model was developed using electromagnetic induction measurements taken with an EM38 instrument in the horizontal mode (EMH) to estimate the chloride concentration in a saturated soil extract in the 0- to 1.2-m depth of irrigated Vertisols. A stepwise linear regression model where the independent variables were soil water storage, exchangeable sodium percentage, and EMH predicted chloride concentration the best. The chloride concentrations thus estimated were similar to measured values only when measured chloride concentrations in the saturated extract were ≤10 meq L?1 (355 mg L?1 = 240 mg kg?1). These values of chloride were then inserted into a chloride mass balance model to estimate deep drainage. In more saline soils, large differences occurred between measured and estimated chloride. Values of drainage based on estimated chloride concentrations in the range of 0–10 meq L?1 were very similar to those based on measured chloride concentrations. There is potential to use an EM38 for quick assessment of deep drainage under irrigated conditions in the field. 相似文献
14.
本文根据Darcy定律和水量平衡原理建立了一种能计算土层初始含水量不均匀的入渗过程的Green—Ampt模型。传统的Green—Ampt模型成为该模型在土层初始含水量均匀情况下的一个特例。本模型除了可直接用于土层水分入渗过程外,稍加修改便可用于多孔介质中液体的扩散过程计算和模拟。 相似文献
15.
Burns’s equation for describing solute movement through soil is attractive because it is simple and predicts adequately in many instances. However, the assumptions implicit in it are not inconsistent with preferential solute flow. We have explored the consequences of this by leaching initially resident chloride and surface-applied tritium and nitrate through 250-mm-long intact cores of a silt loam soil. The applied flow rates of 3 and 5 mm h?1 (realistic rainfall intensities) produced unsaturated soil conditions, except near the base where free water dripped out. Burns’s equation described the movement of the three solutes fairly successfully with the water content parameter having values between 0.29 and 0.48, similar to the actual volumetric water content of 0.47. The leaching of resident chloride to 450-mm-deep mole drains in the field was also successfully simulated using Burns’s equation. However, simulation of the leaching of bromide applied to the soil surface as a solid salt was problematic. This resulted from uncertainty as to whether to treat the application as a pulse input to the flux or resident concentration. The observed behaviour fell about midway between the simulations for these contrasting initial conditions. 相似文献
16.
地膜覆盖滴灌棉田土壤上水分动态的数值模拟 总被引：4，自引：0，他引：4
Drip irrigation under plastic mulch has been widely applied in arid Northwest China as a water-saving irrigation technology.A comprehensive knowledge of the distribution and movement of soil water in root zone is essential for the design and management of irrigation regimes.Simulation models have been proved to be efcient methods for this purpose.In this study,the numerical model Hydrus -2D was used to simulate the temporal variations of soil water content in a drip irrigated cotton field under mulching.A concept of partitioning coefcient,calibrated to be 0.07,was introduced to describe the efect of plastic mulch on prevention of evaporation.The soil hydraulic parameters were optimized by inverse solution using the field data.At the optimized conditions,the model was used to predict soil water content for four field treatments.The agreements between the predictions and observations were evaluated using coefcient of determination (R2) and root mean square error (RMSE).The results suggested that the model fairly reproduced the variations in soil water content at all locations in four treatments,with R2 ranging from 0.582 to 0.826 and RMSE from 0.029 to 0.050 cm3 cm-3,indicating that the simulations agreed well with the observations. 相似文献
17.
18.
19.
水分胁迫条件下绿洲农田冬小麦水分运移规律研究 总被引：5，自引：5，他引：5
以干旱区绿洲农田冬小麦水分胁迫试验为基础,研究了不同水分胁迫条件下的冬小麦生长发育、水分利用以及土壤水分运动特征,建立了含有根系吸水项的一维土壤水动力学模型,模拟了不同水分胁迫条件下冬小麦蒸腾、棵间蒸发、根系吸水、根系生长以及田间土壤水分运移过程。结果表明:在冬小麦生育前期、中期根系吸水主要在80cm以上,生育后期根系对下层土壤水分吸收量增加,但所占比例很小。根据实测根系生长资料分析水分胁迫下生育中期根系受到水分胁迫,在生育后期恢复灌水后根系早衰,生长缓慢;从胁迫程度上来说中度胁迫复水后的后效影响要大于重度胁迫处理。 相似文献
20.
A mathematical model for evaluating the effect of wind on downward-spraying rainfall simulators 总被引：1，自引：0，他引：1
Rainfall simulators are used to study a variety of different processes (e.g., water erosion, infiltration, overland flow, irrigation, movement of agrochemicals, etc.). Wind affects field experiments that make use of rainfall simulators. Water-drop trajectories and velocities are altered, affecting water application and kinetic energy distributions.In this study, a three-dimensional numerical model was developed from the movement of individual drops after their release from the nozzle of a downward-spraying rainfall simulator. Drag forces, wind and gravity affect the original momentum of a single drop. Water application and kinetic energy were estimated from the coupling of a hydrodynamic model for drop movement, a drop generator representing a single full-cone spray nozzle, and an appropriate interception algorithm at the soil surface.The mathematical model should facilitate the selection of single full-cone spray nozzles and the size and configuration of the spray area for rainfall simulation in order to achieve high application uniformity values on the plot area. It can contribute to the adequate choice of nozzles as well as operating conditions necessary for laboratory and field purposes. Laboratory and field experiments were conducted to evaluate the adequacy of the proposed methodology. 相似文献