基于概念模型的棉田土壤水分变化模拟研究

农田土壤水分模拟是农业用水管理的重要依据。以根系层土体水量平衡方程为依据,考虑根系层下界面水分通量,构建了农田土壤水分变化模拟模型,该模型由作物蒸发蒸腾量模型、根区下界面水分通量模型以及水量平衡方程等组成。依据山西水利职业技术学院试验基地2006-2008年3年棉花试验资料,确定了模型参数。结果表明,土壤储水量模拟计算值与实测值有较好的一致性,其相关系数达到0.928 7,F检验结果(F=96.44F0.001=3.27)达到高度显著水平,所建立的土壤水分变化模拟模型可用于棉花田间土壤水分的模拟计算,计算精度平均达到5.3%~15.8%;模型较好地反映了农田土壤水分转化过程以及降水、蒸发和深层土壤水分对作物蒸发蒸腾及产量的影响。     

新疆干旱区膜下滴灌土壤水平衡模拟

膜下滴灌技术是干旱农业区高效节水灌溉的重要手段,以玛纳斯河流域石河子试验站实测数据为基础,运用HYDRUS-2D模型对1膜4行方式下新疆棉田的土壤水运动进行了二维模拟,探讨膜下滴灌在1膜4行覆膜方式下土壤水平衡状况。结果表明,1膜4行覆膜方式下的膜下滴灌技术使新疆棉田无效水分蒸发量以及深层渗漏量大大减少,数值模拟方法可较好地模拟新疆棉田的土壤水平衡状态。上述研究可为宏观尺度上的膜下滴灌模拟与研究提供借鉴,同时对保障干旱区农业生产也有积极作用。     

Could deficit irrigation be a sustainable practice for quinoa (Chenopodium quinoa Willd.) in the Southern Bolivian Altiplano?

The application of deficit irrigation (DI) to stabilize yield and to increase water productivity of quinoa (Chenopodium quinoa Willd.) raises questions in the arid Southern Altiplano of Bolivia where water resources are limited and often saline. Rainfed quinoa and quinoa with irrigation restricted to the flowering and early grain filling were studied during the growing seasons of 2005–2006 and 2006–2007 in a location with (Irpani) and without (Mejillones) water contribution from a shallow water table. It was found that the effect of additional irrigation was only significant above a basic fulfillment of crop water requirements of around 55%. Below this threshold, yields, total water use efficiency (TWUE) and marginal irrigation water use efficiency (MIWUE) of quinoa with DI were low. Capillary rise (CR) from groundwater was assessed using the one-dimensional UPFLOW model. The contribution of water from capillary rise in the region of Irpani ranges from 8 to 25% of seasonal crop evapotranspiration (ET_c) of quinoa, depending mostly on the depth of the groundwater table and the amount of rainfall during the rainy season. DI with poor quality water and cultivation of crops in fields with a shallow saline groundwater table pose a serious threat for sustainable quinoa farming. To assess the impact of saline water resources, soil salinity and required leaching were simulated by combining the soil water and salt balance model BUDGET with UPFLOW. The results indicate that irrigation of quinoa with saline water and/or CR from a saline shallow water table might, already after 1 year, result in significant salt accumulation in the root zone in the arid Southern Altiplano. A farming system with only 1 year fallow is often insufficient to leach sufficient salts out of the root zone. In case the number of fallow years cannot be increased, leaching by means of an important irrigation application before sowing is an alternative. Although potentially beneficial, DI of quinoa in arid regions such as the Southern Bolivian Altiplano should be considered with precaution.     

Simulation of soil water in space and time using an agro-hydrological model and remote sensing techniques

Complete knowledge of all components of the water balance is essential to optimize water use in irrigated agriculture. However, most water balance components are very difficult to measure in terms of the required time interval and due to the complexity of the processes. An unsaturated zone model is a useful tool for predicting the effects of agricultural management on crop water use and can be used to optimize agricultural practices in view of minimizing the agricultural water use. For the irrigated areas in Minqin County of northwest China, the physically based one-dimensional agro-hydrological model SWAP (Soil, Water, Atmosphere and Plant) for water movement and crop growth was applied to reveal all the components of the water balance at multiple sites. This model has a varying level of abstraction referring to simulated processes in time and space. A combination of field, meteorological and aerial data was used as input to the model. Inverse modeling of evapotranspiration (ET) fluxes was followed to calibrate the soil hydraulic functions by using the parameter estimation package PEST. Surface Energy Balance System (SEBS) was used to estimate actual ET fluxes from NOAA AVHRR satellite images. Simulations were carried out for 15 different sites in Minqin County by using wheat (Triticum aestivum L.) as a test crop, but only three sites were selected for model calibration and evaluation. The period of simulation for the whole wheat growing season was from 1 April 2004 to 30 July 2004 and detailed analyses were performed for all sites. SWAP simulated soil water dynamics well and the distributed SWAP model is a useful tool to analyze all water balance components.     

A simulation model of water dynamics in winter wheat field and its application in a semiarid region

Many models for water flow in cropped soil contain parameters such as rooting density, root permeability, and root water potential. Usually these parameters are chosen by trial-and-error method and direct measurements are difficult and impractical in some cases. This study presents a simulation model capable of analyzing water transport dynamics in a soil–plant–atmosphere continuum (SPAC). This model is developed by combining an existing mathematical model for soil water flow, a modified transpiration model taking into account of the air pressure and diurnal changes of the extinction coefficient of crop canopies, and a new simple model for root water uptake. Using data from lysimeters in a field experiment carried out on a wheat crop, we also developed two new empirical equations for the estimation of total canopy resistance and soil evaporation.We then applied the model for 2 years (1990–1991, 1991–1992) on winter wheat in a semiarid area of northwest China. Required parameters, particularly soil hydraulic and crop parameters, were determined by field and laboratory tests. Outputs from the simulation were in good agreement with the independent field measurements of seasonal changes in soil water content, canopy transpiration, surface evaporation, and root water uptake along the soil profile. In addition, this simulation agreed well with the actual measurements of seasonal crop water consumption and soil water balance among the treatments for different irrigation amounts.     

膜下滴灌条件下土壤水盐运移研究综述

将具有保墒增温等优点的地膜覆盖栽培方法,与具有节水增产适时适量的局部浸润滴灌集成创新,形成优势互补相得益彰的膜下滴灌技术,是我国典型的内陆干旱新疆农业节水实践成果,这一技术已在新疆灌区大面积应用,成为我国干旱农业区实施节水灌溉的重要发展模式。随着膜下滴灌技术的应用实践,该技术在具有节水增产、增温保墒等特点的同时,由于膜下滴灌特有的介面特征,显现出在水盐运行环境、运移变化特点、脱盐程度等方面与传统和单一的灌溉方式有着明显不同的特点。综述了近年来新疆灌区有关膜下滴灌条件下的水盐运移、脱盐变化等主要方面试验研究和实践效果,提出了利用膜下滴灌的水盐运移规律而实施脱、排盐应用研究方向。     

膜下滴灌条件下土壤水盐运移研穷综述

将具有保墒增温等优点的地膜覆盖栽培方法，与具有节水增产适时适量的局部浸润滴灌集成创新，形成优势互补相得益彰的膜下滴灌技术，是我国典型的内陆干旱新疆农业节水实践成果，这一技术已在新疆灌区大面积应用，成为我国干旱农业区实施节水灌溉的重要发展模式。随着膜下滴灌技术的应用实践，该技术在具有节水增产、增温保墒等特点的同时，由于膜下滴灌特有的介面特征，显现出在水盐运行环境、运移变化特点、脱盐程度等方面与传统和单一的灌溉方式有着明显不同的特点。综述了近年来新疆灌区有关膜下滴灌条件下的水盐运移、脱盐变化等主要方面试验研究和实践效果，提出了利用膜下滴灌的水盐运移规律而实施脱、排盐应用研究方向。     

葡萄生长对交替滴灌的响应

针对极端干旱区水资源匮乏的现状,以大田葡萄为研究对象,采取根系分区交替滴灌方式研究葡萄生理指标和根区土壤水分分布的变化影响.结果表明:葡萄新枝生长量和叶面积指数随时间的变化过程均可用Logistic模型进行描述,且通过单因素方差分析得出,交替滴灌和常规滴灌的叶面积指数差异不具有统计学意义,说明交替滴灌对植物光合作用主要器官--叶片的生长无明显影响;在棵间蒸发、植物根系吸收以及重力势和水势梯度的共同作用下,交替滴灌条件下沟、垄土壤含水率交替上升,且土壤含水率变化范围主要集中在0~60 cm土层,交替滴灌的耗水量和棵间蒸发量均小于常规滴灌,从而可以提高作物的水分利用效率.该研究为极度干旱区作物节水灌溉提供了一定的科学依据.     

干旱内陆河灌区地面灌溉条件下土壤水盐运动规律研究

通过对干旱内陆河灌区田间土壤水、盐及地下水动态监测试验分析,结果表明:超大水量冬灌方式是导致灌区土壤盐渍化恶性循环的主要原因。对农田土壤盐分的定点实时监测,能够定量表征农田生态环境状况优劣;地下水位埋深变化,可警示农田盐渍化的演变,对调整灌溉定额采取预防措施有指导意义。     

滴灌湿润比对成龄库尔勒香梨树根系分布的影响

在充分灌溉条件下采用3种滴灌湿润比(20%、40%、60%).以漫灌为对照.研究库尔勒成龄香梨吸水根(根直径≤1 mm)在0～70 cm土层内分布的变化,探讨滴灌湿润比对根系分布的影响.结果表明,漫灌成龄库尔勒香梨树吸水根水平方向上在距树体1～2 m内从树行由内向外呈递增趋势;垂直方向上根系随深度呈递增趋势.滴灌对成龄...     

根区等高覆盖灌溉——一种新的农田节水集成配套综合技术初探与展望

结合我国干旱半干旱地区农业生产中普遍存在的农田高效节水灌溉、水肥一体化施肥、秸秆覆盖还田、提高土壤肥力等主要问题,采用农机与农艺相结合的方法,以创新农田高效节水灌溉的技术与方法为中心,同时注重把水肥一体化施肥、秸秆覆盖还田等主要问题与之深度融合,形成一种新的农田节水集成配套综合技术——根区等高覆盖灌溉。在对这一综合技术的概念、实现方式、功能定位等进行初步探讨的同时,对开展根区等高覆盖灌溉综合技术研究前景进行了展望。     

The dual crop coefficient approach using a density factor to simulate the evapotranspiration of a peach orchard: SIMDualKc model versus eddy covariance measurements

The dual crop coefficient approach accounts separately for plant transpiration and soil evaporation by using the basal crop coefficient and the evaporation coefficient, respectively. The SIMDualKc model, which performs the soil water balance simulation with estimation of the actual crop evapotranspiration (ET) with the dual crop coefficient approach, was applied to a drip-irrigated peach orchard under Mediterranean conditions. Orchard ET was obtained with the eddy covariance technique, which was subsequently correlated with tree transpiration estimated from sap flow measurements and soil evaporation determined with microlysimeters, thus providing ET for the whole irrigation season. Two years of field observations were used for model calibration and validation using those ET measurements and taking into account the fraction of ground covered by trees through a density factor which adjusts the basal crop coefficient. Model fitting relative to ET observations during calibration and validation provided indices of agreement averaging 0.90, coefficients of regression close to 1.0, root mean square errors around 0.41 mm and average absolute errors of 0.32 mm. Model fitting relative to transpiration and to soil evaporation produced similar results, so showing the adequateness of modelling.     

内陆河流域绿洲灌区盐碱地改良分区及治理模式探究——以新疆焉耆县平原灌区为例

干旱区土壤盐碱化是土地退化的主要问题,并威胁着绿洲农业的可持续发展,而盐碱地改良分区是因地制宜、综合治理盐碱地的前提。通过综合运用地理信息系统的各种空间数据分析功能,以焉耆平原灌区为典型区域,将土地盐碱化现状分为:非盐碱地、轻度盐碱地、中度盐碱地、重度盐碱地、盐土等5个区,并结合地下水、土壤、植被、岩性等调查资料,进行成因分析,建立了内陆河流域绿洲灌区盐碱地改良分区模型。立足土地盐碱化的现状,充分考虑地下水埋深和矿化度,把焉耆平原灌区按改良难易程度分为:易改良区、较难改良区、难改良区、不宜改良区,并针对不同的盐碱地改良分区特征、水盐平衡模型和现状灌排模式,提出了相应的综合治理对策。     

华北冬小麦-夏玉米农田水分动态模拟研究

冬小麦-夏玉米连作是华北地区主要的粮食作物种植模式。根据华北季节性冻土区的特点,将全年划分为作物生长期与越冬期,分别建立了作物生长条件下农田水分运移模型、冻融条件下土壤水热运移模型。前一模型主要包括参照腾发量计算、腾发量分配、作物根系吸水、土壤表面蒸发、土壤水分特征参数和土壤水分运动等子模型;后一模型主要包括冻土水热耦舍迁移、地气水热交换等子模型。应用以上模型对冬小麦-夏玉米连作条件下的土壤水分过程进行模拟,根据北京永乐店试验资料对模型进行检验。模拟了不同降水水平年、不同灌溉处理下的农田灌溉制度及土壤水分过程,分析了降水、灌溉对农田蒸散、土壤水利用、深层渗漏等的影响。     

The soil water balance of rainfed and irrigated oats,Italian rye grass and rye using the CropSyst model

Crop growth models have been used in simulating the soil water balance for purposes of irrigation management and yield predictions. The application of CropSyst, a cropping systems simulation model, was evaluated for Cedara, South Africa. Simulations included soil water balance of fallow land and rainfed and irrigated winter crops [oats (Avena sativa), Italian ryegrass (Lolium multiflorum) and rye (Secale cereale)]; and irrigation scheduling of the winter crops. Soil, plant, weather and management inputs were used for the soil water balance simulations. Model crop parameters were used from past experiments or obtained from model documentation, with a slight modification to account for varietal differences. The fallow land soil water simulations were more accurate for dry than for wet soil. For all three winter crops, the model consistently over-estimated the soil water content in the upper layers, with a good agreement for the deeper layers until a large precipitation event occurred to which the model responded more slowly than that observed. Simulations using model-scheduled irrigation based on 0.4 and 0.6 maximum allowable depletion criteria indicated that the observed applied irrigation in the field was more than that required. Soil water depletion and accumulated transpiration simulations were similar in both the observed and model-scheduled irrigations, but total soil evaporation and percolation were greater in the case of the observed than the model-scheduled irrigations. Irrigation scheduling using crop growth models may assist in avoiding over- or under-application of irrigation applications by ensuring efficient utilization of rain and irrigation.     

Impacts of water saving on groundwater balance in a large-scale arid irrigation district,Northwest China

Water saving practices are essential for sustainable use of water resources in semiarid regions. To understand the impacts of different water saving measures on groundwater resources, the Hetao Irrigation District in Northwest China was chosen in this study. Based on the data from 1991 to 2010, a groundwater balance model was calibrated and validated. The simulation results showed that irrigation-induced infiltration (92 % of the total groundwater recharge) and groundwater evaporation (92 % of the total groundwater discharge) were the primary factors controlling groundwater table fluctuations during irrigation seasons. The impacts of different water saving scenarios on groundwater balance components were then evaluated. The results revealed that the conjunctive use of water resources was the most effective way to improve water use efficiency (reducing surface water diversions by 52 %) and the depth to groundwater table increased by up to 79 cm. However, deeper groundwater tables may have a negative effect on crop growth due to reduced upward fluxes of groundwater into root zones. Therefore, future studies are needed to evaluate the impacts of different water saving measures on both water resources and crop yields. The results of this study provide further insights into effectively managing water resources in water-limited agricultural areas.     

关于新疆叶尔羌河灌区排水问题的认识

以叶尔羌河灌区为对象, 讨论了内陆干旱区绿洲灌区排水的条件和特点。对内陆干旱区排水的重要特点即旱排与生物排水作出估计, 提出努力实现“水盐平衡”是排水的目标, 在进行排水规划同时也应作出排盐规划     

Water balance and nitrate leaching in an irrigated maize crop in SW Spain

During 3 consecutive years (1991–1993) a field experiment was conducted in an intensively irrigated agricultural soil in SW Spain. The main objective of this study was to determine the water flow and nitrate (N0₃) leaching, below the root zone, under an irrigated maize crop and after the growing season (bare soil and rainy period). The experiment was carried out on a furrow-irrigated maize crop at two different nitrogen (N)-fertilization rates, one the highest traditionally used by farmers in the region (about 500 kg N ha⁻¹ per year) and the other one-third of the former (170 kg N ha⁻¹ per year). The aim was to obtain data that could be used to propose modifications in N-fertilization to maintain crop yield and to prevent the degradation of the environment. The terms for water balance (crop evapotranspiration, drainage and soil water storage) and nitrate leaching were determined by intensive field monitoring of the soil water content, soil water potential and extraction of the soil solution by a combination of neutron probe, tensiometers and ceramic suction cups. Nitrogen uptake by the plant and N0₃-N produced by mineralization were also determined.The results showed that, in terms of water balance, crop evapotranspiration was similar at both N-fertilization rates used. During the irrigation period, drainage below the root zone was limited. Only in 1992 did the occurrence of rainfall during the early growing period, when the soil was wet from previous irrigation, cause considerable drainage. Nitrate leaching during the whole experimental period amounted to 150 and 43 kg ha⁻¹ in the treatments with high and low N-fertilization, respectively. This occurred mainly during the bare soil and rainy periods, except in 1992 when considerable nitrate leaching was observed during the crop season due to the high drainage. Nitrate leaching was not so high during the bare soil period as might have been expected because of the brought during the experimental period. A reduction of N-fertilization thus strongly decreased nitrate leaching without decreasing yield.     

RZWQM: Simulating the effects of management on water quality and crop production

The interactive use of experimentation and modeling is an efficient way to devise and test new agricultural management systems. The Root Zone Water Quality Model (RZWQM) is a comprehensive simulation model designed to predict the hydrologic response, including potential for groundwater contamination, of alternative crop-management systems. The model is one-dimensional (vertical into the soil profile) and integrates physical, biological and chemical processes. It simulates crop development and the movement of water, nutrients and pesticides over and through the root zone for a representative unit area of an agricultural field over multiple years. RZWQM allows for a variety of management practices: tillage; irrigation, fertilizer, manure and pesticide applications; tile drainage and crop rotations. Several significant validation efforts have shown the usefulness of RZWQM for evaluating and developing management scenarios.     

Evaluation of mulched drip irrigation for cotton in arid Northwest China

Field experiments were conducted in arid Southern Xinjiang, Northwest China, for 3 years to evaluate sustainable irrigation regimes for cotton. The experiments involved mulched drip irrigation during the growing season and flood irrigation afterward. The drip irrigation experiments included control experiments, experiments with deficit irrigation during one crop growth stage, and alternative irrigation schemes in which freshwater was used during one growth stage and relatively saline water in the others. The average cotton yield over 3 years varied between 3,575 and 5,095 kg/ha, and the irrigation water productivity between 0.91 and 1.16 kg/m³. Crop sensitivities to water stress during the different growth stages ranged from early flowering-belling (most sensitive) > seedling > budding > late flowering-belling (least sensitive), while sensitivities to salt stress ranged from late flowering-belling > budding > seedling > early flowering-belling. Although mulched drip irrigation during the growing season caused an increase in salinity in the root zone, flood irrigation after harvesting leached the accumulated salts to below background levels. Numerical simulations, based on the 3-year experiments and extended by another 20 years, suggest that mulched drip irrigation using alternatively fresh and brackish water during the growing season and flood irrigation with freshwater after harvesting is a sustainable irrigation practice that should not lead to soil salinization.