Simulation of 1D surface and 2D subsurface water flow and nitrate transport in alternate and conventional furrow fertigation

Increasing water and fertilizer productivity stands as a relevant challenge for sustainable agriculture. Alternate furrow irrigation and surface fertigation have long been identified as water and fertilizer conserving techniques in agricultural lands. The objective of this study was to simulate water flow and fertilizer transport in the soil surface and in the soil profile for variable and fixed alternate furrow fertigation and for conventional furrow fertigation. An experimental data set was used to calibrate and validate two simulation models: a 1D surface fertigation model and the 2D subsurface water and solute transfer model HYDRUS-2D. Both models were combined to simulate the fertigation process in furrow irrigation. The surface fertigation model could successfully simulate runoff discharge and nitrate concentration for all irrigation treatments. Six soil hydraulic and solute transport parameters were inversely estimated using the Levenberg–Marquardt optimization technique. The outcome of this process calibrated HYDRUS-2D to the observed field data. HYDRUS-2D was run in validation mode, simulating water content and nitrate concentration in the soil profiles of the wet furrows, ridges and dry furrows at the upstream, middle and downstream parts of the experimental field. This model produced adequate agreement between measured and predicted soil water content and nitrate concentration. The combined model stands as a valuable tool to better design and manage fertigation in alternate and conventional furrow irrigation.     

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。     

层状土溶质运移特性及其参数分析

由于自然和人为因素作用,土壤常常呈现层状结构,这种层状结构影响土壤水分和溶质的运移特性。通过室内模拟试验,分析了层状土溶质运移特性,研究了层状土溶质运移参数变化特征。结果表明C l-在层状土及均质土中弥散度具有明显差异,并且这种差异与夹层土壤的弥散度存在密切相关。     

地膜覆盖对土壤棵间蒸发影响的研究

农作物地膜覆盖栽培技术是 2 0世纪 80年代发展起来的新技术 ,其保温、保墒和增产效果明显 ,但不同地膜覆盖率对减少土壤棵间蒸发影响规律 ,目前国内研究不多。通过在室内研究覆膜灌溉土壤蒸发规律 ,研究出不同土壤含水率的水分蒸发和不同覆盖率对土壤蒸发的影响关系 ,并在田间进行验证。为今后定量评价农作物地膜覆盖减少土壤棵间蒸发提供理论依据     

不同覆盖方式对土壤水分分布的影响

在位于典型半湿润灌区的山东农业大学农业生态实验站研究了冬小麦秸秆覆盖与起垄覆膜沟内播种(膜垄)2种覆盖模式的土壤水分时空动态变化。结果表明,秸秆覆盖能有效提高冬小麦30 cm以下土壤含水率,膜垄对0-30 cm土壤含水率的提高贡献最大。进入拔节期后,随着冬小麦生育进程的推进,膜垄在30-120 cm土层含水率降幅较大,形成一个水分亏缺带,而秸秆覆盖在该土层的含水率一直较高。该试验表明,膜垄在保水保墒和土壤水分垂直分布方面表现出与秸秆覆盖完全不同的特点。     

覆膜开孔条件下斥水性层状土壤蒸发实验

覆膜开孔影响田间非均质土壤的水分运动过程,尤其当斥水程度不同时,其运动过程更趋于复杂.在控制土表不同覆膜开孔率条件下,进行了不同斥水程度的塿夹砂和砂夹塿的土柱蒸发实验,测定和分析了不同条件下土壤水分蒸发量变化过程和含水率剖面.结果表明,全覆膜的累积蒸发量-时间曲线明显较低,相应的蒸发10d后土壤水分剖面也与初始水分剖面接近,对于塿夹砂尤其明显.覆膜开孔率增加时,同条件下两种层状土的累积蒸发量与全覆膜相比均有明显增加,表明一旦覆膜开孔,覆膜保墒效应便明显降低.斥水程度增加时,累积蒸发量有所减小,说明斥水性的存在降低了水分运移速率.当土壤为严重斥水时,斥水性对水分运动过程的影响比覆膜开孔率的影响更明显.对于不同斥水程度的塿夹砂,采用对数函数表达累积蒸发量和时间的定量关系较好,而对于不同斥水程度下的砂夹塿分别采用幂函数和对数函数表达.     

免耕覆盖条件下田间土壤水分入渗的二维数值模拟研究

根据土壤水动力学基本原理,建立了秸秆覆盖条件下夏玉米SPAC系统中二维土壤水分入渗模型,应用该模型采用ADI法对辽宁地区秸秆覆盖条件下玉米田间土壤水分入渗过程进行模拟计算。模拟结果再现田间土壤水分入渗过程,同时显示产流与未产流情况试验数据与模拟值均有较好的一致性,平均相对误差均在5%以内,所构建模型可用于覆盖条件下土壤水分运动规律的研究。     

水稻覆膜旱作栽培技术试验稻田地膜效应的研究

根据姚李水文试验站 3年试验资料 ,重点介绍稻田覆膜后具有保温、保墒、保肥的效应及群体生育性状效应和节水、增产对比效益分析 ,为该项目的进一步发展提供理论依据     

Comparison of measured and simulated water storage in dryland terraces of the Loess Plateau, China

In the hilly regions of China, developing sustainable agriculture requires implementing conservation management practices that prevent soil erosion and conserve soil and water resources. In the semiarid northwest Loess Plateau, the primary conservation management practice is terracing. Numerical simulation of soil water dynamics in terraces is potentially an efficient means of investigating the effects of terrace design on moisture retention, but little information is available on the accuracy of such simulations. In this work, we evaluated the accuracy of HYDRUS-2D simulations of water infiltration and redistribution in fallow, level, dryland terraces located in the Loess Plateau. The simulated soil water content distributions were in good agreement with experimental data. Modeling analyses showed that about one-third of the evaporative water losses occurred from the terrace riser surface. To prevent such losses, it is advisable to mulch the riser and minimize the riser surface area. The simulations also demonstrated that with other dimensions equal, wide terraces retain more water on a percentage basis than narrow ones due to a lower evaporating surface area are per unit volume of water storage. With other design considerations being equal, wide beds and minimal riser surface areas will likely enhance water capture and retention. Future analyses of terrace moisture dynamics may additionally include simulations of root water uptake, surface ponding, and runoff.     

不同位置秸秆覆盖条件下土壤水盐运动实验研究

以地下水与土壤水动力学理论为基础,通过对不同地下水埋深不同位置秸秆覆盖试验资料分析,建立了土壤水分运动数学模型,并进行了数值模拟,试验实测数据与模型计算值吻合较好,说明所建立的模型是可行的。并以此为基础,分析了不同地下水埋深不同位置秸秆覆盖土壤含盐量,得出地表以下30 cm处秸秆覆盖的土壤含盐量大于地表表层秸秆覆盖的土壤含盐量,这为新疆地区控制潜水蒸发改良盐碱地研究提供了可靠的基础依据。     

西北干旱区滴灌棉田膜间土壤蒸发试验研究

膜间土壤蒸发是覆膜棉田水分消耗的主要组成部分,在干旱少雨的新疆石河子利用微型蒸渗仪观测了地下滴灌和膜下滴灌条件下,覆膜棉田膜间土壤水分蒸发,并对膜间不同位置处的土壤蒸发规律进行了试验研究,研究结果表明,滴灌条件下膜间土壤水分蒸发分别与气温、辐射、饱和水汽差以及相对湿度呈指数相关关系,与参考作物需水量呈线型相关关系,与表层土壤含水率呈指数关系;膜间土壤累积蒸发量在苗期最高、其次是花铃期、吐絮期最小;膜下滴灌条件下膜边土壤的蒸发量高于膜间（两条膜正中间的裸地）蒸发量;地下滴灌条件下,错位种植会导致灌溉水的无效蒸发,不利于灌溉水的高效利用。     

An explicit hydrological algorithm for basic flow and transport equations and its application in agro-hydrological models for water and nitrogen dynamics

Hydrological simulation is a key component in argo-hydrological models for optimizing resources use and minimizing the environmental consequences in agriculture. In this study we extended a simple and explicit algorithm for solving the basic soil water flow equation by Yang et al. (2009) to the solute transport equation. The key feature of the algorithm is to use a uniform soil layer thickness and a small time step in solving the soil water and solute transport equations, so that the calculations can be made on a layer basis. This drastically simplifies the procedure of modeling water and solute transport in soil using the basic equations. The proposed algorithm was tested against the complex finite element (FE) numerical scheme in simulating soil water and solute transport in different soils via numerical experiments. The results showed that the proposed algorithm with a uniform soil layer thickness of 5 cm and a small time step of 0.001 d was able to achieve the identical accuracy as the FE method. Tests of the proposed algorithm in simulating water and nitrogen dynamics against data from a field experiment on wheat revealed that the predicted results with the simple algorithm were in good agreement with the time-course measurements of soil water and mineral N concentration at the various depths in the profile, suggesting that the proposed algorithm performed well and can be reliably applied in agro-hydrological models. The simplicity and accuracy of the algorithm will encourage scientists to use basic equations for soil water and solute transport more in the future for improving performance of agro-hydrological models.     

加氧灌溉对菠萝根区土壤呼吸和生理特性的影响

通过大田试验,研究了加氧灌溉对菠萝根区土壤呼吸作用、生理特性、生物量积累、果实产量、品质和水分利用效率的影响.采用Mazeei（空气注射器）给地下灌溉系统加入空气,设计了加氧和不加氧灌溉2种处理方式,7次重复.设计滴头埋深10 cm.研究表明,与对照相比,菠萝根区30 cm以内土壤水分质量分数和CO2质量分数没有明显差异,但是加氧灌溉使得土壤呼吸增加了100%;菠萝的果实鲜重、生物量鲜重、干物质重和收获指数明显增大,差异有统计学意义（p≤0.05）;加氧灌溉提高了菠萝的水分生产率,与对照相比增加了17.2%;同时,加氧灌溉明显改善了菠萝单果尺寸和重量,使得单果重量增加了17.3%,田间产量增加了4.3%,增加了果实的糖质量分数,减少了果实的透明物.研究结果为加氧灌溉技术的推广应用提供了理论依据.     

干旱区大田膜下滴灌对土壤盐分的影响

为研究干旱区大田膜下滴灌土壤盐分运移特征,在新疆石河子炮台试验站进行连续4年的试验研究。结果表明,膜下滴灌条件下,边行盐分偏高,棵间土壤盐分上升;耕作层土壤盐分下降,耕作层以下则增加,但由于滴灌灌水频繁,作物根系分布层内(0～40cm)土壤盐分始终处于较低值;利用膜下滴灌可以明显降低盐荒地土壤盐分,加速盐荒地改良和弃耕地的收复。     

土壤质地对坡地土壤水分运动与转化特征的影响研究

通过室内模拟降雨试验,研究了杨凌塿土、安塞黄绵土和神木绵砂土的水分迁移特征。结果表明,随着土壤粘粒含量的增加,坡面产流开始时间提前,坡地平均径流系数、径流量和泥沙量呈增加趋势,入渗率和累计入渗水量呈减少趋势。3种土壤降雨入渗率均可用Kostiakov公式拟合,塿土、黄绵土和绵砂土坡地的平均入渗率分别为0.32、0.83和0.88 mm/min。湿润锋运移速度应该与土壤砂粒百分含量和土层含水量的增量呈正相关关系。为了提高雨水利用率,减少水土流失量,建议加强塿土坡地的保护性耕作措施。     

Response of hot pepper (Capsicum annuum L.) to mulching practices under planted greenhouse condition

Mulch is considered a desirable management technology for conserving soil moisture, improving soil temperature and soil quality. This study aimed to investigate soil conditions and hot pepper (Capsicum annuum L.) performance in terms of leaf photosynthetic capacity, fruit yield and quality, and irrigation water use efficiency (IWUE) under such practices in greenhouse condition. A field experiment across 3 years was carried out with four types of mulch (without mulch [CK], wheat straw mulch [SM], plastic film mulch [FM], and combined mulch with plastic film and wheat straw [CM]). Mulch could improve soil physical properties regardless of mulch materials. FM and CM treatments improved soil moistures status and soil temperature in comparison to CK control, while SM increased soil water content and decreased soil temperature. Mulch increased leaf net photosynthesis rate (P_N), stomatal conductance to water vapor (gs), intercellular CO₂ concentration (Ci), and transpiration rate (E), but declined instant water use efficiency (WUEi). No significant effect of mulch application on chlorophyll fluorescence was existent for the entire growth season. Fruit yield and irrigation water use efficiency (IWUE) showed some increment under all the mulch conditions. Compared to CK, the yield was enhanced by 82.3%, 65.0%, and 111.5% in 2008; 38.1%, 17.4%, and 46.5% in 2009; and 14.3%, 6.5%, and 19.6% in 2010 under SM, FM, and CM conditions, respectively. Although FM produced better fruit quality than other treatments, CM is the recommended practice for hot pepper cultivation in greenhouse condition due to working well to facilitate soil condition (moisture and temperature), plant growth, and marketable yield.     

基于HWSD的GSAC模型网格化产流参数估计与校正

针对基于网格的萨克拉门托模型(GSAC)产流参数难以估计的问题,提出利用世界和谐土壤数据库(HWSD)土壤属性数据估计和校正该模型产流参数的方法。首先,采用HWSD土粒百分含量和土壤质地分类数据估算流域各网格顶层(T层)与底层(S层)土壤的凋萎系数、田间持水量、饱和含水量等土壤水分常数;再采用一个气候指数和HWSD的T层张力水容量、田间持水量及凋萎系数推求GSAC模型上层厚度,继而利用上层厚度将流域各网格的HWSD土壤水分常数转换为GSAC模型上、下层土壤水分常数;最后利用GSAC模型上层厚度与转换了的土壤水分常数估计流域各网格的产流参数;在估计产流参数的同时,采用12个系数对这些产流参数进行校正,所有的校正系数通过自由搜索(FS)算法率定GSAC模型确定。呼兰河流域的应用结果表明:基于HWSD土壤属性数据估计GSAC模型网格化产流参数的方法简便易行,利用校正产流参数驱动的GSAC模型在率定期与验证期的纳什效率系数(NSEC)分别为0.81和0.83,与不校正产流参数情况相比,校正产流参数的GSAC模型能够取得更高的模拟精度。     

土壤溶质优先迁移影响因素研究进展

根据国内外学者对土壤溶质优先迁移的研究成果和进展,详细分析了土壤内部普遍存在的水分运动——优先迁移现象,系统综述了土壤结构和质地、土壤初始含水率、林木根系、石砾、降雨强度、灌溉模式等影响因素。最后简要总结和探讨了溶质优先迁移发展趋势。     

基于HYDRUS-2D/3D的玉米全膜双垄沟水肥运移规律与根系响应

为研究西北旱区玉米全膜双垄沟种植模式下土壤水肥运移规律,通过HYDRUS-2D/3D模型对甘肃省定西市玉米全膜双垄沟土壤水肥运移规律及根系响应进行数值模拟,分析全膜双垄沟播种植模式下土壤含水率及垄沟内种肥浓度的分布规律,在合理播深处设置观测点以表征土壤含水率及膜下氮、磷、钾水肥互作运移变化规律。模拟结果表明,全膜双垄沟膜下渗水孔与种穴位置处土壤水肥发生环状侧渗现象,其中土壤含水率范围为15.20%~17.12%,垄沟内氮肥转化浓度趋于15.38mg/L,磷肥转化浓度趋于5.15mg/L,钾肥转化浓度趋于12.21mg/L,水肥主要集中在垄沟位置,保障了苗期水肥需求;通过施加根系吸水和水肥运移模拟表明全膜双垄沟模式下土壤水肥条件满足玉米出苗需求。研究模型与结果将为玉米全膜双垄沟农艺技术的优化提升提供理论依据。     

微灌地膜的节水保墒增温效应研究

在实验基础上 ,分析论述了微灌地膜的节水效果和增温保墒效应。试验结果表明 ,微灌地膜可比地面灌溉节水 61 % ,增加地温 3℃～ 6℃ ,近地面空气相对湿度提高 3 0 %～ 40 % ,综合效应明显。可供微灌地膜或膜下微灌的进一步研究设计参考