膜下滴灌土壤盐分特性及影响因素的初步研究

针对新疆盐碱地的改良特征，通过室内膜下滴灌土壤盐分运移试验，初步研究了土壤脱盐过程，滴头流量、灌水量等对脱直听影响。结果表明：膜下滴灌土壤盐分分布可划为达标脱盐区、未达标脱盐区及积直3个区域；土壤含盐量分布具有水平脱盐距离大于垂直脱盐距离的特点，滴头流量、土壤初始不量以及土壤初始含盐量的增加不利于达标脱盐区的形成；灌水量的增加有助于土壤脱盐。这些结果对膜下滴灌新技术开发利用盐碱地的生产实践有指标意义。     

土槽模拟开沟覆膜滴灌技术下盐分调控规律

新疆气候干旱与土壤盐碱化并存,是制约新疆农业发展的主要因素,开沟覆膜滴灌技术综合了膜下滴灌技术与开沟技术的优点,理论上可有效治理盐碱地。在开沟覆膜滴灌技术下,设置不同灌水定额与灌水次数,利用试验土槽模拟盐分调控规律,结果表明:1第1次合适灌水定额对盐分的淋洗起主要作用,可使土体盐分达到较稳定的状态,盐分也随水分侧向运移,并在土埂表层聚集;2灌水定额的增加促进盐分随水分向远离滴头和向深层方向运移,使得覆膜间、覆膜边盐分淋洗的深度增加,脱盐区增加;3在灌水定额为300m3/hm2时,可以在滴灌带横向0~23cm,下部58cm处迅速形成一个含盐量小于1.5%的达标脱盐区,满足当地作物正常出苗,故建议当地可选择300m3/hm2作为第1次灌水洗盐定额。     

不同灌水技术参数对农田水盐运移的影响

【目的】探索滴灌条件下农田高效洗盐适宜灌溉指标。【方法】通过人工控水试验重点研究了不同滴头流量(2.8和5.6L/h)和灌水定额(22.5、37.5和52.5mm)对盐碱地棉花根区盐分淋洗效果的影响。【结果】同一灌水定额条件下,湿润锋半径随着滴头流量的增加而增大;滴头流量增加,土壤水分分布呈宽浅型,表层土壤含水率逐渐升高。同一滴头流量条件下,湿润锋半径随着灌水定额的增加而增大;土壤含水率随着灌水定额的增加而增大。表层土壤盐分随着滴头流量和灌水定额的增大而减小,滴头流量为2.8 L/h时,水平脱盐半径30 cm,垂直脱盐深度60 cm;滴头流量为5.6 L/h时,水平脱盐半径40 cm,垂直脱盐深度40 cm。【结论】灌水定额52.5 mm时,脱盐效果最佳;随着作物的根部伸长,改变滴头流量,扎根40 cm以内用滴头流量5.6 L/h,扎根超过40 cm用滴头流量2.8L/h,可作为适宜的灌水技术参数。     

北疆常年膜下滴灌棉田土壤盐分积累特征研究

根据6块北疆常年膜下滴灌棉田生育期内4a的土壤盐分监测资料,分析了不同膜下滴灌年限棉田土壤盐分的积累特征。结果表明,膜下滴灌棉田各层土壤盐分随着种植年限的增加先减少后增加。膜下滴灌前6a,棉田各层土壤初始含盐量较高,随着膜下滴灌年限的增加,表层土壤盐分受滴灌淋洗作用不断减小,各层土壤呈脱盐趋势;膜下滴灌种植6a后,由于灌水量的限制,膜下滴灌不具有深层淋洗作用,积盐区土壤盐分随着膜下滴灌年限的增加不断向上扩大,很容易受到温度、灌水制度、地下水位抬升、蒸发等影响,从而在耕作层附件形成多个积盐区,造成土壤返盐,威胁作物生长发育,使作物死亡或减产,甚至造成土壤次生盐碱化。因此,对种植年限6a的棉田要及时进行漫灌,对于膜下滴灌年限更久的棉田要增加漫灌次数或缩短漫灌周期。如果没有漫灌条件,可以尝试在每年生育期末进行1次或2次穿插灌水,从而抑制盐分上移。     

盐碱地膜下滴灌水盐运移规律试验研究

通过室内模拟实验,进行灌水量恒为10 L,采用土壤初始含水率为7.6%、14.8%和21.3%及滴头流量为1 L/h、2 L/h和3 L/h,探求土壤初始含水率和滴头流量对盐碱土水盐运移的影响,结果表明:在相同灌水量及滴头流量下,随着土壤初始含水率的增大,滴头附近高含水率的区域增大,水分水平运移速率减小,垂向运移速率增大,利于水分的向下运移,在水平方向的脱盐区域减小,而在垂向的脱盐区域明显增大;在相同的土壤始含水率条件下,随着滴头流量的增大,水分水平运移距离增大,水平脱盐效果明显,而垂向脱盐区减小,小滴头流量利于土壤中盐分的向下运移,有助于压盐;以滴头为中心,湿润锋水平、垂向运移距离及两滴头湿润锋交汇宽度与时间t具有良好的幂函数关系。     

滴灌条件下斥水土壤水盐运移试验研究

通过室内滴灌入渗的三维水盐运移试验,分析了斥水和亲水土壤在相同滴头流量下的湿润锋变化规律,研究了轻微斥水土壤的湿润锋随时间变化规律、含水率的三维空间分布特征以及不同斥水度土壤中含盐量和Cl-浓度分布特点。结果表明,在相同的滴头流量(0.07mL/min)下,亲水土壤与轻微斥水土壤的水平、垂直湿润锋与入渗时间具有良好的幂函数关系;亲水土壤与轻微斥水的土壤含盐量与距滴头距离符合良好的二阶多项式关系;虽然定量结果不同,但总体上轻微斥水的土壤在入渗中仍与亲水土壤具有相似的水分、盐分分布特征。在轻微斥水的农田中,滴灌灌水技术仍可为作物创造有利的水盐环境。     

棉花滴灌田间盐分变化规律的初步研究

以田间实验为基础对棉花滴灌土壤盐分的变化规律进行了分析研究。结果表明：滴灌为浅灌且可控性强，不会产生深层渗漏，土壤含盐量在整个滴灌期较低。盐分在空间的分布主要受蒸发和湿润区范围的影响，灌水量的增加有助于土壤脱盐。这些结果对在生产实践中控制滴灌水量和治理盐碱具有指导意义。     

滴头流量对风沙土滴灌湿润锋运移影响的试验研究

为了在风沙土地区更为合理的利用滴灌技术,通过室内试验模拟了单点源和双点源滴灌条件下风沙土土壤水分运移过程,研究了不同滴头流量下土壤湿润锋时空动态分布规律。结果表明灌水时间相同时,滴头流量越大,湿润锋运移距离越大;灌水量相同时,滴头流量增大对湿润锋水平运移距离影响较小,但可增大垂直方向运移距离。大流量滴头增大了湿润锋初始运移速度,随着灌水时间的增加,湿润锋运移速度迅速减小并趋于稳定,且不同流量处理之间差异较小。双点源滴灌时,入渗交汇前水分运动规律与单点源入渗规律相同;滴头流量越大,湿润体交汇时间越短,交汇处湿润锋运动速度越快;但滴头正下方含水量高,土壤含水量径向变化较大,增加了土壤含水量空间分布的不均匀性。     

田间点源入渗试验的水盐分布特征分析

通过田间点源入渗试验,研究了田间点源入渗土壤水盐分布特征,得出以下结论:①滴头下方距滴头距离较近的区域,滴头流量较小的处理土壤含盐量较小;距滴头距离较远的区域,滴头流量较大的处理土壤含盐量较小.水平方向土壤含盐量变化相似;②表层土壤盐分随着入渗时间的增加而减小.滴头下方土壤含盐量总体上随着入渗水量的增加而减小,入渗水对土壤中的盐分的淋洗效率和压盐深度均与入渗时间成正比.     

田间点源入渗试验的水盐分布特征

通过田间点源入渗试验,研究了田间点源入渗土壤水盐分布特征,得出以下结论：（1）滴头下方距滴头距离较近的区域,滴头流量较小的处理土壤含盐量较小;距滴头距离较远的区域,滴头流量较大的处理土壤含盐量较小。水平方向土壤含盐量变化相似;（2）表层土壤盐分随着入渗时间的增加而减小。滴头下方土壤含盐量总体上随着入渗水量的增加而减小,入渗水对土壤中的盐分的淋洗效率和压盐深度均与入渗时间成正比。     

微咸水波涌畦灌对土壤水盐分布的影响

根据2005年在中国科学院南皮生态农业试验站的田间试验结果,对灌溉后土壤剖面和沿畦长方向的水盐分布进行了研究.结果表明,当灌水量相同时,灌水结束后波涌灌和连续灌0～100 cm土层含水率在整个畦田上存在较大差别.比较灌水均匀度的结果可知,供水时间为90 min时,N=3,r=1/2,T_(on)=30 min的处理含水率离散程度最小,灌水均匀度最满意.从主根区含盐量的变差系数来看,连续灌明显高于波涌灌,说明微咸水的波涌灌在畦首到畦尾的盐分分布离散程度低于连续灌.因此灌水方式的改变在不增加灌水量的条件下改善了土壤水盐分布状况.     

咸淡轮灌和生物炭对滨海盐渍土水盐运移特征的影响

为利用滨海地区微咸水改良盐渍土,进行了不同咸淡水轮灌(淡淡、淡咸、咸淡、咸咸)和施用生物炭(0、15、30 t/hm2)的室内入渗试验,探讨了咸淡轮灌和生物炭施用下滨海盐渍土水盐运移过程.结果表明:滨海盐渍土水分运动主要受初始入渗水质的影响,先咸后淡的轮灌方式更有利于土壤水分入渗,入渗速率增加了8.2％～46.9％,并...     

Modelling soil water and salt dynamics under pulsed and continuous surface drip irrigation of almond and implications of system design

The HYDRUS-2D model was experimentally verified for water and salinity distribution during the profile establishment stage (33?days) of almond under pulsed and continuous drip irrigation. The model simulated values of water content obtained at different lateral distances (0, 20, 40, 60, 100?cm) from a dripper at 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, 140 and 160?cm soil depths at different times (5, 12, 19, 26 and 33?days of profile establishment) were compared with neutron probe measured values under both irrigation scenarios. The model closely predicted water content distribution at all distances, times and soil depths as RMSE values ranged between 0.017 and 0.049. The measured mean soil water salinity (ECsw) at 25?cm from the dripper at 30, 60, 90 and 150?cm soil depth also matched well with the predicted values. A correlation of 0.97 in pulsed and 0.98 in continuous drip systems with measured values indicated the model closely predicted total salts in the root zone. Thus, HYDRUS-2D successfully simulated the change in soil water content and soil water salinity in both the wetting pattern and in the flow domain. The initial mean ECsw below the dripper in pulsed (5.25?dSm^?1) and continuous (6.07?dSm^?1) irrigations decreased to 1.31 and 1.36?dSm^?1, respectively, showing a respective 75.1 and 77.6% decrease in the initial salinity. The power function [y?=?ax ^?b ] best described the mathematical relationship between salt removal from the soil profile as a function of irrigation time under both irrigation scenarios. Contrary to other studies, higher leaching fraction (6.4–43.1%) was recorded in pulsed than continuous (1.1–35.1%) irrigation with the same amount of applied water which was brought about by the variation in initial soil water content and time of irrigation application. It was pertinent to note that a small (0.012) increase in mean antecedent water content (θ _i ) brought about 8.25–9.06% increase in the leaching fraction during the profile establishment irrespective of the emitter geometry, discharge rate, and irrigation scenario. Under similar θ _i , water applied at a higher discharge rate (3.876?Lh^?1) has resulted in slightly higher leaching fraction than at a low discharge rate (1.91?Lh^?1) under pulsing only owing to the variation in time of irrigation application. The influence of pulsing on soil water content, salinity distribution, and drainage flux vanished completely when irrigation was applied daily on the basis of crop evapotranspiration (ETc) with a suitable leaching fraction. Therefore, antecedent soil water content and scheduling or duration of water application play a significant role in the design of drip irrigation systems for light textured soils. These factors are the major driving force to move water and solutes within the soil profile and may influence the off-site impacts such as drainage flux and pollution of the groundwater.     

多点源滴灌条件下土壤水分运移模拟试验研究

为了指导密植作物的滴灌系统合理设计,通过室内物理试验模拟了多点源滴灌条件下土壤水分运移过程,重点研究了不同滴头流量下交汇湿润体内的土壤水分时空动态分布规律．多点源滴灌条件下土壤水分运动遵循先点源入渗、再湿润锋交汇和最后形成湿润带的规律．灌水结束时,土壤水分分布呈现湿润体上部复杂、下部相对简单的特征．湿润体上部,在滴头下方存在土壤含水率相对较高的区域,2个滴头之间近地表处存在土壤含水率相对较低的区域;湿润体下部同一深度土层上的含水率有趋于一致的趋势．灌水结束后,由于土壤水分再分布,同一深度土层上含水率差异逐渐减小．灌水量相同条件下,灌水结束时,滴头流量小的入渗深度较大,湿润体内土壤平均含水率较低;灌水结束后,受土壤水分再分配的作用,不同滴头流量下入渗深度的差异较灌水结束时有所减小．     

A review of models for predicting soil water dynamics during trickle irrigation

Designing drip irrigation systems involve selection of an appropriate combination of emitter discharge rate and spacing between emitters for any given set of soil, crop, and climatic conditions, as well as understanding the wetted zone pattern around the emitter. The exact shape of the wetted volume and moisture distribution will depend on many factors, including soil hydraulic characteristics, initial conditions, emitter discharge rate, application frequency, root characteristics, evaporation, and transpiration. Multi-dimensional nature of water flow, plant uptake and high frequency of water application increase the complexity in modelling soil moisture dynamics from trickle irrigation. Researchers used analytical methods, semi-analytical methods and numerical methods to Richards’ equation using certain boundary conditions to model the infiltration from point source irrigation for use in design, install, and manage of drip irrigation systems due to their merits over direct measurements. Others developed models based on Green-Ampt equation, empirical models using regression techniques/dimensional analysis techniques/moment approach techniques/artificial neural networks on this topic to describe infiltration from a point/line sources. A review on these models developed under each category is presented in this study. Other knowledge gaps identified include (a) effect of variations in initial moisture content and packing conditions, (b) precision in observing the wetting front and soil–water content, (c) validity of soil surface boundary conditions, (d) effect of crop root architecture and its withdrawal pattern for different input parameters, (e) effects of gravitational gradients, (f) stratification in the soils, and (g) impact of soil hysteresis. The review promotes better understanding of the soil water dynamics under point source trickle emitters and helps to identify topics for more emphasis in future modelling activity.     

盐碱地滴灌对新疆杨生长及土壤盐分分布影响

通过田间试验研究高垄覆膜滴灌模式下不同土壤基质势对盐碱地新疆杨生长以及土壤盐分分布的影响。试验设5个水平的土壤基质势处理：-5kPa（S1）,-10kPa（S2）,-15kPa（S3）,-20kPa（S4）,-25kPa（S5）,每个处理重复3次,按随机区组布置。试验结果表明,2009年生育末期,根系周围土体中的盐分比...     

无压地下灌溉新技术试验

对局部控水灌溉(无压地下灌溉)技术从理论上进行了分析，并给出了其土壤水分运动方程。在大田试验的基础上，研究分析了无压灌溉不同孔径孔口出水规律和根区局部湿润状况。试验结果表明：无压孔口出水规律与孔口孔径、地温和土壤含水量等因素有关；出水孔口孔径和初时土壤含水量对湿润锋推进速度影响较大，孔径和初时土壤含水量越大，湿润锋推进速越快；适宜的出水孔径沿管道长度方向出水均匀，5～35cm深度的土壤含水量变化无明显差异，能够满足作物需水和生理需水要求。     

微咸水膜孔沟灌土壤水盐分布与灌水质量分析

通过田间试验,研究了微咸水膜孔沟灌下流量和开孔率对土壤水盐分布和灌水质量的影响。结果表明,田面水流推进时间和距离符合幂函数分布,流量和开孔率对水流推进速度影响较大;膜孔沟灌通过降低水分蒸发,抑制盐分表聚,有效调节了土壤水盐分布,总体上,对0~40cm土层盐分具有明显淋洗作用;灌水效率Ea随开孔率的增大而增大,随流量的变化不明显;灌水均匀度Ed随流量的增大而减小,随开孔率的增大而减小;脱盐效率Es随开孔率的增大先增大后减小,随流量的变化不明显;通过方差分析对灌水质量影响因素进行排序,初步得出试验区适宜的膜孔沟灌优化灌水技术组合。     

Emitter discharge characteristics of vertical tube irrigation affected by various factors

To examine the working principle of vertical tube irrigation, variations in vertical tube emitter discharge and their causes were analyzed in the laboratory experiment. The effects of the pressure head, initial soil water content, and tube diameter on the emitter discharge of the vertical tube were studied. The quantitative relationship between the time and cumulative infiltration and emitter discharge of the vertical tube was obtained, and R² was more than 0.98. Emitter discharge exhibits a positive and negative correlation with the pressure head and soil water content, respectively. Tube diameter has a nonsignificant effect on the emitter discharge. Changes in the soil water content around the emitter water outlet are the main causes of emitter discharge variations. In the experiments, the range of vertical tube emitter discharge was 0.056-1.102 L/h. The emitter of vertical tube irrigation automatically adjusts the soil water content and maintains the root zone soil water content within an appropriate range, thus achieving continuous irrigation, in order to achieve the effect of water-saving.     

Distribution and dynamics of soil water and salt under different drip irrigation regimes in northwest China

A 2-year experiment was carried out to investigate the effects of different drip irrigation regimes on distribution and dynamics of soil water and salt in north Xinjiang, China. Five treatments—F7 (0.24 dS m^?1 + Once every 7 days), B7 (4.68 dS m^?1 + Once every 7 days), S7 (7.42 dS m^?1 + Once every 7 days), F10 (0.24 dS m^?1 + Once every 10 days) and F3 (0.24 dS m^?1 + Once every 3 days)—were designed. For all treatments, additional 150-mm fresh water was applied on 10th November in 2009 (winter irrigation) to leach the accumulated salt. The results revealed that irrigation frequency and water quality had significant effects on the spatial distribution and change of soil water content, soil salt and the crop water consumption rate, but had a limited impact on the seasonal accumulative water consumption, and the cotton yield decreased with the decrease in irrigation frequency and water quality on the whole. During the cotton growing season, results showed that the salt mainly accumulated in the 0- to 60-cm soil layer, while the soil salt in 60- to 100-cm layer changed slightly, indicating that the drip irrigation could not leach the soil salt out of the root zone under the irrigation regimes. Therefore, salt leaching was necessary to maintain the soil water–salt balance and to prevent excessive salt accumulation in the root zone. After the 150-mm winter irrigation and subsequent thawing, soil salts were leached into the deeper layers (below 60 cm), and the soil salt content (SSC) (EC_1:5) in root zone in the next year was about 0.2 dS m^?1. Moreover, compared to 2009 season, the SSC within the root zone did not increase even the EC of the irrigation water was up to 7.42 dS m^?1. Additionally, it is important to note that the results were concluded based on the data of the 2-year experiment; further studies are need to optimize winter irrigation amount and assess the sustainability of saline water irrigation since long-term utilization of saline water may lead to soil degradation.