滴灌条件下核桃园土壤水分动态变化的数值模拟研究

为探究滴灌条件下核桃根系对土壤含水量的影响,试验以8 a生核桃树为研究对象,使用分层分段挖掘法分析核桃根系的空间形态分布,通过构建HYDRUS-2D模型,对有根系吸水下的土壤水分变化进行求解,并利用实测点数据校验2D模型的可用性。经过实际计算与理论分析,得出如下结论:在垂直二维剖面中,水平距树0~30 cm、垂直40~60 cm土层的细根根长密度分布最大,为1 618.216 m·m~(-3)。对比实测数据与模拟数据,结果显示RMSE均小于0.0186 cm~3·cm~(-3),ME绝对值小于0.0108 cm~3·cm~(-3),证明数值模拟效果较好,HYDRUS模型可应用于实际试验研究。将根系模块纳入模型模拟,并比照单独水流模块作用,结果显示根系对土壤含水量产生影响,使体积含水率曲线整体低于单独水作用下的含水率曲线,且两者关系差异性显著。模拟核桃生育前期土壤含水量变化,结果表明灌水后6 d至7 d内,土壤含水量存在明显减小现象,故可将生育前期灌水周期设定为6 d或7 d。     

基于HYDRUS-1D的秸秆覆盖条件下黑土区玉米田土壤水盐运移规律

为揭示不同秸秆覆盖量对黑土区玉米田农田土壤水盐运移的影响机制,基于田间试验结果,利用HYDRUS-1D模型对秸秆覆盖下农田土壤水盐运移过程进行模拟,分析不同秸秆覆盖量对土壤水盐动态的影响规律。结果表明：秸秆覆盖可以增强土壤保水性、抑制土壤盐分积累,随秸秆覆盖量增加,秸秆覆盖对土壤水盐运移的作用效果更加明显,在玉米全生育期内秸秆半量覆盖及全量覆盖较裸地40 cm耕层内各土层平均含水率分别提高3.38%~5.78%和5.26%~9.62%、平均电导率分别降低4.61%~8.93%和8.87%~12.41%。基于HYDRUS-1D模型模拟结果可知,土壤含水率模拟值与实测值的决定系数介于0.903~0.940,标准误差介于0.010~0.014 cm³·cm^-3,平均相对误差介于3.46%~4.64%;土壤电导率模拟值与实测值的决定系数介于0.817~0.853,标准误差介于0.091~0.111 mS·cm^-1,平均相对误差介于4.06%~5.46%。误差分析表明HYDRUS-1D模型模拟精度较高,能够用于模拟研究区秸秆覆盖条件下农田土壤水盐运移过程。     

Root length density distribution and associated soil water dynamics for tomato plants under furrow irrigation in a solar greenhouse

Furrow irrigation is a traditional widely-used irrigation method in the world. Understanding the dynamics of soil water distribution is essential to developing effective furrow irrigation strategies, especially in water-limited regions. The objectives of this study are to analyze root length density distribution and to explore soil water dynamics by simulating soil water content using a HYDRUS-2D model with consideration of root water uptake for furrow irrigated tomato plants in a solar greenhouse in Northwest China. Soil water contents were also in-situ observed by the ECH_2O sensors from 4 June to 19 June and from 21 June to 4 July, 2012. Results showed that the root length density of tomato plants was concentrated in the 0–50 cm soil layers, and radiated 0–18 cm toward the furrow and 0–30 cm along the bed axis. Soil water content values simulated by the HYDRUS-2D model agreed well with those observed by the ECH_2O sensors, with regression coefficient of 0.988, coefficient of determination of 0.89, and index of agreement of 0.97. The HYDRUS-2D model with the calibrated parameters was then applied to explore the optimal irrigation scheduling. Infrequent irrigation with a large amount of water for each irrigation event could result in 10%–18% of the irrigation water losses. Thus we recommend high irrigation frequency with a low amount of water for each irrigation event in greenhouses for arid region. The maximum high irrigation amount and the suitable irrigation interval required to avoid plant water stress and drainage water were 34 mm and 6 days, respectively, for given daily average transpiration rate of 4.0 mm/d. To sum up, the HYDRUS-2D model with consideration of root water uptake can be used to improve irrigation scheduling for furrow irrigated tomato plants in greenhouses in arid regions.     

基于HYDRUS模型的暗管排水水盐运移模拟

为了探索暗管排水条件下膜下滴灌农田的水盐运移规律,本文设计了埋深1 m,间距4 m的暗管排水模型试验,研究分析灌水淋洗过程中土壤水分和盐分的动态变化规律,并利用HYDRUS模型对暗管排水条件下的水盐运移规律进行数值模拟分析与验证。结果表明：经过3次灌水淋洗后,表层0~20 cm土层内盐分含量下降至2 g·kg^-1,达到了非盐化土水平,20~60 cm土体内上层土壤脱盐效果高于下层,总盐分含量下降至8 g·kg^-1以下;经过实测值与模拟值的验证,土壤盐分和水分的均方根误差RMSE最大分别为0.632和1.324,决定系数R²最小分别为0.992和0.906,说明模拟结果与实测结果吻合度较好,HYDRUS模型能够较好地模拟暗管排水过程中水盐运移规律。通过模型模拟6次灌水（共90 d）后暗管排水条件下不同土层深度的水盐动态变化特征,模拟结果表明,0~40 cm土层内盐分含量下降至2 g·kg^-1,40~80 cm土层内盐分含量下降至4 g·kg^-1左右,基本达到轻度盐化水平;距离暗管不同间距处的土壤剖面盐分含量呈波动变化,距离暗管越远,土壤剖面含盐量越大,盐分含量在0~8 g·kg^-1范围内变化。     

基于HYDRUS-2D模型模拟耕荒地水盐运移规律

在野外实测资料的基础上,利用HYDRUS-2D模型对作物生育期耕地与盐荒地间土壤水盐的迁移进行了模拟和分析。结果表明,在强蒸发作用下,盐分在表层土壤中积聚,20、40、70 cm土层分别上升了67.23%、62.37%、37.2%。经检验,HYDRUS-2D模型对土壤含水率和含盐率运移的模拟具有较高精度,反映出盐分积聚和水分运移规律。     

Application of SALTMED and HYDRUS-1D models for simulations of soil water content and soil salinity in controlled groundwater depth

Salinization is a gradual process that should be monitored. Modelling is a suitable alternative technique that saves time and cost for the field monitoring. But the performance of the models should be evaluated using the measured data. Therefore, the aim of this study was to evaluate and compare the SALTMED and HYDRUS-1 D models using the measured soil water content, soil salinity and wheat yield data under different levels of saline irrigation water and groundwater depth. The field experiment was conducted in 2013 and in this research three controlled groundwater depths, i.e., 60(CD60), 80(CD80) and 100(CD100) cm and two salinity levels of irrigation water, i.e., 4(EC4) and 8(EC8) d S/m were used in a complete randomized design with three replications. Soil water content and soil salinity were measured in soil profile and compared with the predicted values by the SALTMED and HYDRUS-1 D models. Calibrations of the SALTMED and HYDRUS-1 D models were carried out using the measured data under EC4-CD100 treatment and the data of the other treatments were used for validation. The statistical parameters including normalized root mean square error(NRMSE) and degree of agreement(d) showed that the values for predicting soil water content and soil salinity were more accurate in the HYDRUS-1 D model than in the SALTMED model. The NRMSE and d values of the HYDRUS-1 D model were 9.6% and 0.64 for the predicted soil water content and 6.2% and 0.98 for the predicted soil salinity, respectively. These indices of the SALTMED model were 10.6% and 0.81 for the predicted soil water content and 11.0% and 0.97 for the predicted soil salinity, respectively. According to the NRMSE and d values for the predicted wheat yield(9.8% and 0.91, respectively) and dry matter(2.9% and 0.99, respectively), we concluded that the SALTMED model predicted the wheat yield and dry matter accurately.     

基于HYDRUS-1D的不同质地土壤入渗过程数值模拟

基于HYDRUS-1D软件,对不同土质(淤泥、粉砂壤土、砂质粘壤土)的灌溉方案进行了系统的数值实验,模拟灌溉结束时及灌溉结束24 h之后的土壤剖面含水量和土壤湿润锋的变化情况。结果表明:在不产生径流的情况下,灌溉结束24 h后土壤的含水量分布和湿润深度只与土壤种类和灌溉量有关,与灌溉速度无关;对透水性较好的土质,灌溉水分重分布明显,以粉砂壤土灌溉速率0.7 cm·h~(-1)和灌溉时间3 h为例,灌溉结束时和灌溉24 h后土壤湿润深度分别为9.2 cm和20.6 cm,有55.3%的灌溉水参加了水分重分布;土壤湿润深度与灌溉量之间存在线性关系,拟合直线的斜率介于5.15(淤泥)和5.95(砂质黏壤土)之间。     

利用HYDRUS-2D模拟膜下滴灌玉米农田深层土壤水分动态与根系吸水

河套灌区农田地下水埋深普遍较浅且年内波动较大,明确不同膜下滴灌条件下深层土壤水分对根区的补给作用及作物根系吸水的响应差异有利于膜下滴灌技术的完善和推广。本研究开展了连续2 a(2017—2018年)的春玉米田间试验,设置3个膜下滴灌灌溉水平,分别控制土壤基质势下限为-10 kPa(S1)、-30 kPa(S3)和-50 kPa(S5)。利用HYDRUS-2D模型模拟0～120 cm深度土壤含水量、根层下边界(100 cm深度处)水分通量和作物根系吸水速率。结果表明,经过率定后的HYDRUS-2D模型对0～120 cm深度土壤含水量模拟结果的根均方差(RMSE)和决定系数(R~2)分别为0.039～0.042 cm~3·cm~(-3)和0.78～0.73,模拟结果可靠。膜下滴灌农田100 cm和120 cm深度处土壤含水量较高且处理间差异不大,说明不同滴灌条件对于100 cm以下深层土壤含水量影响较小;但不同处理显著影响根区下边界的水分通量和根系吸水速率。基质势下限控制水平越低,深层土壤水分对于根区的补给量(毛管上升)越大,S1、S3、S5生育期内累积补给量在31.9～49.6 mm之间。S5处理根系吸水速率较低,根系吸水受到显著抑制,从而造成作物生长指标和产量显著低于S1和S3处理(P0.05);而S1和S3之间籽粒产量差异不显著。综上,在本研究所设置的3个滴灌处理中,S3生育期内灌溉定额为240～300 mm,既较S1显著减少灌水量、提高水分利用效率,又具有较好的根系活力,有效利用深层土壤水分,因此建议该地区春玉米膜下滴灌的灌水下限为-30 kPa。     

不同降雨历时梯田和坡耕地的土壤水分入渗特征

以黄土高原丘陵沟壑第三副区庄浪县为例,研究不同降雨历时条件下坡耕地和水平梯田土壤(黄绵土)水分入渗变化特征,应用Hydrus-1D模型对不同降雨条件下的土壤水分入渗进行定量模拟研究。结果表明:(1)与实测数据相比,Hydrus-1D模型模拟降雨后土壤水分的运移较合理。(2)地表层(0~40 cm)土壤含水量变异系数(CV)呈中等变异,即5 d的时间内梯田和坡耕地地表层的土壤含水量变化大,随着土层深度的增加变异系数减小,呈弱变异性。(3)在1.45 mm/min降雨强度下,在23 min时拔节期的小麦坡耕地产生径流,水平梯田在整个过程中没有产生径流。(4)降雨历时为10 min时,在土层深度为0~15 cm,梯田土壤含水量比坡耕地多0.13%~1.65%,在土层深度为30~200 cm,梯田和坡地都没有下渗。降雨历时为20min、30min时,在土层深度为0~20 cm,梯田的土壤含水量比坡耕地的分别多0.05%~2.22%、0.01%~2%。     

微咸水膜下滴灌棉田春灌压盐效果的初步分析

在塔里木盆地平原灌区,微咸水灌溉意义重大。而微咸水灌溉的最大问题是土壤积盐,经过1 a的微咸水灌溉后,来年播种前是否需要冬灌或春灌压盐是人们关注的焦点。通过对比尉犁县3个微咸水膜下滴灌棉田监测区（S1,S2,S3）,2010年春灌前0~60 cm土壤易溶盐含量和棉籽发芽期、苗蕾期、花铃期与吐絮期棉花生长的耐盐指标（分别为7.1 g/kg,6.9 g/kg,8.2 g/kg和9.2 g/kg）,得出了S1和S2隔年压盐一般能满足棉花发芽及生长的要求,而S3监测区仍需要春灌压盐的结论。计算得出3个监测区的春灌前后土壤脱盐率分别为11.9%~84.2%,20.7%~71.1%和32.9%~78.8%,表明3个监测区的春灌压盐效果均很明显。     

基于HYDRUS模型的盐碱地土壤水盐运移模拟

为了解陕西卤泊滩盐碱地的水盐运移情况,基于当地2009—2013年田间水盐监测资料,应用饱和-非饱和土壤水分及溶质运移理论,利用HYDRUS-1D数值模型对当地土壤水分、盐分运移规律进行数值模拟,分析了盐碱地的水盐变化状况,确定合理的田间灌水定额。结果表明:在玉米整个生育期内,不同灌溉处理的土壤含水量变化趋势基本一致,从节水控盐的综合标准衡量,农田灌水定额为500 m3·hm-2时有利于控制土壤盐分的累积。采用HYDRUS-1D模型对盐碱地农田土壤水盐运移的模拟结果与田间试验实测结果基本吻合,该研究结果可为类似盐碱化地区农田水盐管理提供科学依据。     

不同灌排模式下土壤盐分动态模拟与评价

利用HYDRUS-1 D模型对不同灌排模式下土壤水盐运移进行一维数值模拟,分析比较了节水灌溉和常规灌溉、暗管排水和无排水对盐碱地的改良效果.结果表明,节水灌溉模式下耕作层含盐量的年内变化规律与常规灌溉相似,在节水14.36%的情况下不会明显降低耕作层的洗盐效率;在连续常规灌溉和节水灌溉条件下耕作层的土壤盐分呈逐年减少的...     

起垄沟播和常规平播下滴灌棉田土壤水盐的运移

为明确滴灌条件下植棉方式对土壤水盐运移的影响,采用田间调查与室内分析相结合的方法,在滨海重度盐碱地开展了起垄沟播和常规平播植棉方式下的水盐运移试验,调查了滴灌前后两种植棉方式不同点位及不同土壤深度的土壤水分、盐分和土壤溶液电导率等指标,分析不同植棉方式土壤水分、盐分和土壤溶液电导率的时空分布特征。结果表明：滴灌条件下起垄沟播的水分入渗深度和盐分淋洗深度均明显大于常规平播植棉方式,起垄沟播植棉膜下(0~20 cm)土壤溶液电导率明显低于常规平播植棉;滴灌对两种种植方式膜外土壤水分和盐分运移未产生明显影响。起垄沟播联合滴灌技术更有利于为棉花生长的水盐环境。研究结果可为盐碱地植棉提供理论参考和实践依据。     

灌水量对全膜垄作沟灌玉米产量及水分利用效率的影响

针对河西灌区水资源紧缺的问题,探索玉米合理的灌溉量,以期指导区域玉米合理灌溉。通过在石羊河流域设置不同的灌水量梯度,研究不同灌水量对全膜垄作沟灌玉米产量及水分利用效率,以及土壤含水率、产量要素的影响。结果表明:全膜垄作沟灌玉米灌水量从4 500 m~3·hm~(-2)增加到4 725 m~3·hm~(-2)、4 950 m~3·hm~(-2)时,产量并没有随着灌水量的增加而增加,灌水量增加到5 175 m~3·hm~(-2)时,在水分利用效率没有降低的情况下,产量相对于4 500、4 725 m~3·hm~(-2)和4 950 m~3·hm~(-2)处理明显增加11.46%、8.39%和8.54%,其中果穗长度、穗粒数和百粒重平均增加4.88%、3.27%和4.31%是其产量增加的主要原因。对于土壤含水率,玉米需水盛期的7月16日至8月3日,5 175 m~3·hm~(-2)处理显著高于其他三个处理,而灌浆期各处理间则差异不显著。与播前期相比,收获期土壤含水率降低层主要集中在20~80 cm土层,土层贮水量平均降低6.72 mm,且各处理0~110 cm土层贮水量差异并不明显。因此,本研究表明5 175 m~3·hm~(-2)为石羊河流域全膜垄作沟灌条件下的适宜灌溉量,但灌浆中后期的最后一次灌水应考虑适当降低灌水量。     

基于HYDRUS-2D的雨水集聚深层入渗系统土壤水分运移模拟

为了解雨水集聚深层入渗(RWCI)系统土壤水分的入渗规律,设置不同灌水量(10 L、21 L和36 L)和RWCI设计坑深(40 cm和60 cm)的室内土箱试验,观测不同灌水量与不同水头变化情况土壤含水率变化和土壤湿润锋在径向和垂直方向上运移过程,依据非饱和土壤水动力学理论,建立HYDRUS-2D变水头边界条件土壤水分二维入渗模型。通过与实测数据对比,结果表明模型模拟值和实测值具有较好一致性:垂向湿润锋相对均方差(R_E)、平均绝对误差(MAE)和纳什系数(NE)分别为0.019、0.011 cm和0.994,径向湿润锋R_E、MAE和NE分别为0.018、0.851 cm和0.977,土壤含水率R_E、MAE和NE分别为0.188、0.016 cm~3·cm~(-3)和0.916。相比于设计深度为40 cm的RWCI系统, 60 cm RWCI系统在不同灌水量下能够更有效地增加果树根系分布层的土壤含水率,增加土壤水分入渗深度;相同灌水量下RWCI系统设计深度的径向湿润锋分布间无明显差异,而垂直方向的分布具有明显差异;RWCI系统在相同的设计深度下,随着灌水量增大湿润锋在垂向与径向的运移距离差异逐渐增大。     

甘肃河西地区不同储水灌溉和生育期灌溉农田水分特征分析

对甘肃河西地区不同储水灌溉和生育期灌溉农田水分特征进行了试验研究.结果表明:在河西地区,冬季储水灌溉定额为180 mm的处理,其生育期剖面的土壤水分较多地分布在140～160 cm,且土壤含水量达到30%以上,容易发生深层渗漏;较小的储水灌溉定额,土壤水分主要分布在0～100 cm范围内,不会引起土壤剖面水分的深层渗漏.冬季储水灌溉定额愈大,春播前农田无效土壤蒸发也愈大.冬季储水灌溉定额相同,生育期灌溉定额大的处理其剖面含水量高,且分布愈深,深层土壤的水分渗漏也愈大.总的灌水定额相同,冬季储水灌溉和生育期灌溉比较,生育期灌溉定额较大的处理,剖面水分的分布主要集中在0～100 cm的土层内,没有出现易发生深层渗漏较高的水分分布.在小麦生育期,总的灌溉定额相同的条件下,冬季储水灌溉定额大的处理,0～200 cm土壤水分有亏缺,冬季储水灌溉定额大或生育期灌溉定额大,农田腾发量也愈大.适中的储水灌溉定额,不仅有利于作物的生长,还有利于灌溉水分利用效率的提高.     

Soil water and salt distribution under furrow irrigation of saline water with plastic mulch on ridge

Furrow irrigation when combined with plastic mulch on ridge is one of the current uppermost water-saving irrigation technologies for arid regions.The present paper studies the dynamics of soil water-salt transportation and its spatial distribution characteristics under irrigation with saline water in a maize field experiment.The mathematical relationships for soil salinity,irrigation amount and water salinity are also established to evaluate the contribution of the irrigation amount and the salinity of saline water to soil salt accumulation.The result showed that irrigation with water of high salinity could effectively increase soil water content,but the increment is limited comparing with the influence from irrigation amount.The soil water content in furrows was higher than that in ridges at the same soil layers,with increments of 12.87% and 13.70% for MMF9(the treatment with the highest water salinity and the largest amount of irrigation water) and MMF1(the treatment with the lowest water salinity and the least amount of irrigation water) on 27 June,respectively.The increment for MMF9 was gradually reduced while that for MMF1 increased along with growth stages,the values for 17 August being 2.40% and 19.92%,respectively.Soil water content in the ridge for MMF9 reduced gradually from the surface layer to deeper layers while the surface soil water content for MMF1 was smaller than the contents below 20 cm at the early growing stage.Soil salinities for the treatments with the same amount of irrigation water but different water salinity increased with the water salinity.When water salinity was 6.04 dS/m,the less water resulted in more salt accumulation in topsoil and less in deep layers.When water salinity was 2.89 dS/m,however,the less water resulted in less salt accumulation in topsoil and salinity remained basically stable in deep layers.The salt accumulation in the ridge surface was much smaller than that in the furrow bottom under this technology,which was quite different from traditional furrow irrigation.The soil salinities for MMF7,MMF8 and MMF9 in the ridge surface were 0.191,0.355 and 0.427 dS/m,respectively,whereas those in the furrow bottom were 0.316,0.521 and 0.631 dS/m,respectively.The result of correlation analysis indicated that compared with irrigation amount,the irrigation water salinity was still the main factor influencing soil salinity in furrow irrigation with plastic mulch on ridge.     

甘肃河西地区膜下滴灌条件下春玉米田水盐特征分析

通过对甘肃河西地区膜下滴灌春玉米种植条件下土壤水分、盐分的观测,分析了膜下滴灌春玉米生育期土壤水分、盐分动态变化及其产量和水分利用效率。结果表明:不同生育期,同一土层深度,土壤水分含量高低分布与土壤盐分含量高低分布相反,均表现出土壤不同深度盐分含量高的区域相应水分含量低,滴灌带之间土壤盐分积累较滴头之间显著;灌水定额480 m~3·hm~(-2)处理,灌溉水分在土层纵向运移显著,深层渗漏明显,灌水定额420 m~3·hm~(-2)处理,灌溉水在土壤不同深度横向层面运移显著,有利于作物吸收利用;膜下滴灌能够在滴水过程中明显降低土壤表层0~40 cm盐分含量,土壤下层40~100 cm为盐分聚集区域;灌水定额420 m~3·hm~(-2)处理,春玉米产量构成和水分利用效率较高。从作物生长水盐环境及高效节水的角度出发,灌水定额420 m~3·hm~(-2)处理的效益最优。     

半干旱山区积盐果园集雨灌溉洗盐效果研究

以甘肃省秦安县兴国镇郑川村盐分胁迫果园土壤为研究对象,研究了集雨灌溉对果园土壤剖面盐分离子和果树生长的影响.结果表明:在淋洗前后全盐(P=0.001<0.01)和水溶性Na+(P=0.000<0.01)有极显著的差异,Cl~-(P=0.040<0.05)和水溶性Ca~(2+)(P=0.045<0.05)有显著的差异,而K~+、Mg~(2+)、HCO_3~-、CO_3~(2-)和SO_4~(2-)在淋洗前后差异不显著.通过果园土壤淋洗,能够明显改善树体的生长状况,叶缘焦枯的叶片逐渐恢复正常.     

鲁北平原咸水滴灌对土壤水盐分布和棉花产量的影响

鲁北平原是山东省重要的粮棉油生产基地,合理利用微咸水和咸水资源是亟待解决的问题。通过田间小区试验,以淡水滴灌处理为对照,设置不同矿化度咸水滴灌处理,研究全地膜覆盖条件下,咸水滴灌对棉花农田土壤水盐分布和产量的影响。结果表明,灌出苗水可以明显降低棉田主要根层土壤EC值,降低率在26．8％～29．0％之间。咸水滴灌减少了棉花对土壤水分的吸收,主要影响土层在40～100 cm,灌溉水矿化度越高,影响越大。与淡水滴灌相比,滴灌补灌矿化度6g·L-1以下的咸水对棉花产量没有明显的影响,而滴灌8g·L-1的咸水在降水偏少的年份能明显降低棉花产量。从土壤盐分的积累来看,利用滴灌补灌一次6g·L-1以下的咸水,通过黄河水和夏季降水淋洗土壤盐分,不会造成棉花根系分布层土壤盐分的积累。该研究结果可为鲁北平原区咸水利用提供科学依据。