Evaluation of capacitance probes for optimal irrigation of citrus through soil moisture monitoring in an entisol profile

 Continuous monitoring of soil moisture content within and below the rooting zone can facilitate optimal irrigation scheduling aimed at minimizing both the effects of water stress on the plants, and also the leaching of water below the root zone, which can have adverse environmental effects. The use of Sentek capacitance probes (EnviroSCAN RT5) in scheduling citrus irrigation was evaluated using 3-year-old Hamlin orange trees [Citrus sinensis (L.) Osb.] on Swingle citrumelo rootstock [Citrus paradisi Macf. × Poncirus trifoliata (L.) Raf.] grown in a Candler fine sand (hyperthermic, uncoated, Typic Quartzipsamments). Available soil moisture calculated according to capacitance probe readings of soil moisture agreed well with that calculated using soil water release curves determined in the laboratory. A utility program was developed to process the data collected by the capacitance probe into a spreadsheet format. Processed data were used to calculate soil water storage within and below the citrus root zone at desired time intervals. Irrigation set points (i.e., full point equivalent to maximum desirable water storage and refill points I and II) were defined based on field capacity determined both in the field and in the laboratory and permanent wilting point. It was possible to maintain the water content in the root zone between the full and refill points I and II during most of the growing season. Although soil water content in the root zone exceeded the full point during periods of high irrigation, it drained rapidly within 24–48 h after the end of such irrigation events. Using soil moisture depletion in the root zone during periods of low water application to estimate citrus evapotranspiration (ET), the calculated daily average ET during 10-day period in November was 1.33 mm day⁻¹. Received: 11 August 1998     

Estimating in situ soil–water retention and field water capacity in two contrasting soil textures

A priori knowledge of the in situ soil field water capacity (FWC) and the soil-water retention curve for soils is important for the effective irrigation management and scheduling of many crops. The primary objective of this study was to estimate the in situ FWC using the soil-water retention curve developed from volumetric water content (θ), and water potential (ψ) data collected in the field by means of soil moisture sensors in two contrasting-textured soils. The two study soils were Lihen sandy loam and Savage clay loam. Six metal frames 117 cm × 117 cm × 30 cm high were inserted into the soil to a depth of 5–10 cm at approximately 40 m intervals on a 200 m transect. Two Time Domain Reflectrometry (TDR) sensors were installed in the center of the frame and two Watermark (WM) sensors were installed in the SW corner at 15 and 30 cm depths to continuously monitor soil θ and ψ, respectively. A neutron probe (NP) access tube was installed in the NE corner of each frame to measure soil θ used for TDR calibration. The upper 50–60 cm of soil inside each frame was saturated with intermittent application of approximately 18–20 cm of water. Frames were then covered with plastic tarps. The Campbell and Gardner equations best fit the soil–water retention curves for sandy loam and clay loam soils, respectively. Based on the relationship between soil ψ and elapsed time following cessation of infiltration, we calculated that the field capacity time (t _FWC) were reached at approximately 50 and 450 h, respectively, for sandy loam and clay loam soils. Soil-water retention curves showed that θ values at FWC (θ _FWC) were approximately 0.228 and 0.344 m³ m⁻³, respectively, for sandy loam and clay loam soils. The estimated θ _FWC values were within the range of the measured θ _FWC values from the NP and gravimetric methods. The TDR and WM sensors provided accurate in situ soil–water retention data from simultaneous soil θ and ψ measurements that can be used in soil-water processes, irrigation scheduling, modeling and chemical transport.     

土壤剖面水分线性尺度测量方法

针对现有土壤水分点尺度下测量的局限性,提出了一种线性尺度下的土壤剖面水分测量方法,并设计了一种基于驻波比法的土壤剖面水分信息测量传感系统。借助HFSS高频电磁场仿真软件与网络矢量分析仪对传感器环形探头的电场强度分布情况与阻抗特性进行了分析研究,确定了环形探头适应性与敏感区域。以2种不同质地的土壤作为试验样本,对土壤水分传感器的输出与对应的测量值进行了多项式拟合,决定系数均达到了0.99以上,传感器的稳态与动态性能均能满足土壤剖面水分的测量要求。通过多层水分土柱穿层试验与对比试验表明,该系统能够满足线性尺度下土壤剖面水分的实时测量需求,具有较高的测量精度与稳定性。设计的土壤剖面水分线性测量系统的各项指标均达到实际应用的需求,具有较高的应用推广价值。     

Groundwater table and salinity: Spatial and temporal distribution and influence on soil salinization in Khorezm region (Uzbekistan, Aral Sea Basin)

Groundwater (GW) management is an essential element in irrigated agriculture. This paper analyzes the temporal dynamics of GW table and salinity in Khorezm, a region of Uzbekistan which is situated on the lower Amu Darya River in the Aral Sea Basin and suffering from severe soil salinization. We furthermore identify the critical areas for potential soil salinization by examining GW table and salinity measured during 1990–2000 in 1,972 wells, covering the entire region. Additionally, case studies were performed to assess the contribution of the GW to the soil salinization on a field scale. Over the entire area, GW was only moderately saline averaging 1.75 ± 0.99 g l⁻¹ However, GW levels were generally very shallow averaging 148 ± 57 cm below the ground surface and thus likely to prompt secondary soil salinization. Three case studies where GW table, soil and GW salinity were closely monitored at the field scale, suggested that the elevated GW levels forced soil salinization by annually adding 3.5–14 t ha⁻¹ of salts depending on the position and salinity of the GW table. Maps interpolated from the regional dataset revealed that GW was significantly shallower and more saline in the western and southern parts of Khorezm despite the presence of a drainage network which is rather uniformly distributed throughout the region. The results of the current study will assist the development of an improved drainage management in Khorezm.     

4种常见土壤含水量传感器精度分析及评价

针对目前市面上不同传感器测定结果差异过大,导致农业生产中效率低下的问题,选取了市面上常见的4种土壤湿度传感器（编号为A、B、C和D）,进行室内与田间试验,测试传感器的精度。试验结果表明,传感器B的测定结果与土壤真实含水量值最为接近（综合误差为5.14%）,而其他3种传感器测定值与真实含水量的差异较大（综合偏差均＞9%）。此外,当测试环境变化时,传感器对于相同含水量土壤的测定结果会随之变化,传感器测定误差值也随之变化,特定条件下误差值变化相当明显。测试也表明传感器厂家对传感器的初步校正具有局限性,如果想得到更为精确的结果,对传感器再次进行针对校正是必不可少的。      

Elevation and infiltration in a level basin. I. Characterizing variability

Spatial characterization of soil physical properties could improve the estimation of surface irrigation performance. The aim of this research was to characterize the spatial and time variability of a set of irrigation-related soil properties. The small-scale experimental level-basin (729 m²) was located on an alluvial loam soil. A corn crop was established in the basin and irrigated five times during the season. A detailed survey of the soil properties (generally using a 3 × 3 m network) was performed. Classic statistical and geostatistical tools were used to characterize the variables and their interactions. Semivariograms were validated for the studied variables, except for the clay fraction, the saturated hydraulic conductivity and the infiltration parameters. The resulting geostatistical range was often in the interval of 6–10 m. For the three surveys of soil surface elevation the range was smaller, about 4 m. No correlation was found between saturated hydraulic conductivity and the other soil physical properties. Soil surface elevation showed a high correlation between surveys. After the first irrigation, the standard deviation of elevation increased from an initial 9.6 mm to 20.8 mm. The soil physical parameters were used to map the soil water management allowable depletion. In a companion paper these results are used to explain the spatial variability of corn yield and soil water recharge due to irrigation. Received: 24 February 1998     

A method for spatial prediction of daily soil water status for precise irrigation scheduling

Available water holding capacity (AWC) and field capacity (FC) maps have been produced using regression models of high resolution apparent electrical conductivity (EC_a) data against AWC (adj. R² = 0.76) and FC (adj. R² = 0.77). A daily time step has been added to field capacity maps to spatially predict soil water status on any day using data obtained from a wireless soil moisture sensing network which transmitted hourly logged data from embedded time domain transmission (TDT) sensors in EC_a-defined management zones. In addition, regular time domain reflectometry (TDR) monitoring of 50 positions in the study area was used to assess spatial variability within each zone and overall temporal stability of soil moisture patterns. Spatial variability of soil moisture within each zone at any one time was significant (coefficient of variation [% CV] of volumetric soil moisture content (θ) = 3-16%), while temporal stability of this pattern was moderate to strong (bivariate correlation, R = 0.52-0.95), suggesting an intrinsic soil and topographic control. Therefore, predictive ability of this method for spatial characterisation of soil water status, at this site, was limited by the ability of the sensor network to account for the spatial variability of the soil moisture pattern within each zone. Significant variability of soil moisture within each EC_a-defined zone is thought to be due to the variable nature of the young alluvial soils at this site, as well as micro-topographic effects on water movement, such as low-lying ponding areas. In summary, this paper develops a method for predicting daily soil water status in EC_a-defined zones; digital information available for uploading to a software-controlled automated variable rate irrigation system with the aim of improved water use efficiency. Accuracy of prediction is determined by the extent to which spatial variability is predicted within as well as between EC_a-defined zones.     

围框淹灌仪器法测定土壤田间持水量试验研究

田间持水量是重要的土壤水分常数之一,是开展墒情评价和旱情分析,指导科学灌溉不可缺少的基础信息。传统的土壤田间持水量测定方法操作复杂,给土壤墒情评价带来一定难度。通过将先进的无线土壤测量传感技术与传统的围框淹灌法相结合,提出了一种基于无线传感器的新方法,利用“滑动平均含水量法”和“移动平均法”计算确定土壤田间持水量,并在陕西、北京、吉林和河北不同土壤类型的农田开展验证试验。结果表明,与传统环刀法相比,围框淹灌仪器法测定结果的平均相对误差为4.89%,不同质地土壤上测定结果均比较稳定,两种方法测定的田间持水量随土层深度的变化规律一致。围框淹灌仪器法测定土壤田间持水量具有可靠性和便捷实用性,是土壤墒情监测与评价的有效方法,适宜推广应用。      

Comparison and sensitivity of measurement techniques for spatial distribution of soil salinity

In Khorezm, a district of Uzbekistan situated in the Aral Sea Basin, soil salinization is an important driver of soil degradation in irrigated agriculture. The main objective of this study was to identify techniques that enable rapid estimation of soil salinity. Therefore, bulk electrical conductivity of the soil (EC_a-meas) was measured with three different devices (2P, 4P, and CM-138) and electrical conductivity of the soil paste (EC_p-meas) was measured with the so-called 2XP device. These measurements were compared with independent estimates of EC_a-calc and EC_p-calc based on laboratory measurements of the saturated extract, EC_e, of soil samples from the same sites. Soil salinity could be assessed satisfactorily with all four devices. EC_p-meas could be well reproduced by the 2XP device (R ² = 0.76), whereas EC_a-meas estimates using 2P, 4P, and CM-138 in the field were less accurate (R ² < 0.50). The sensitivity of all devices to the main ions Cl⁻ and Ca^{2 +} suggests that the measuring principles are similar for all instruments. The devices can therefore be used interchangeably. Field assessment of soil salinity was considerably enhanced by the use of CM-138, because large areas can be quickly assessed, which may be desirable in spite of the lower accuracy.     

Surface energy balance model of transpiration from variable canopy cover and evaporation from residue-covered or bare-soil systems

A surface energy balance model based on the Shuttleworth and Wallace (Q J R Meteorol Soc 111:839–855, 1985) and Choudhury and Monteith (Q J R Meteorol Soc 114:373–398, 1988) methods was developed to estimate evaporation from soil and crop residue, and transpiration from crop canopies. The model describes the energy balance and flux resistances for vegetated and residue-covered surfaces. The model estimates latent, sensible and soil heat fluxes to provide a method to partition evapotranspiration (ET) into soil/residue evaporation and plant transpiration. This facilitates estimates of the effect of residue on ET and consequently on water balance studies, and allows for simulation of ET during periods of crop dormancy. ET estimated with the model agreed favorably with eddy covariance flux measurements from an irrigated maize field and accurately simulated diurnal variations and hourly amounts of ET during periods with a range of crop canopy covers. For hourly estimations, the root mean square error was 41.4 W m⁻², the mean absolute error was 29.9 W m⁻², the Nash–Sutcliffe coefficient was 0.92 and the index of agreement was 0.97.     

基于准静态同轴探头模型的土壤复介电测量方法

末端开路同轴探头法测量土壤复介电值用于表征土壤含水率具有准确、快捷的优点。针对目前土壤介电同轴探头集总测量模型没有充分考虑探头的参数以及土壤体积对测量结果影响等问题,基于电磁场理论,对末端开路同轴探头建立了准静态数学模型,适用于土壤的复介电常数准确测量。通过全波软件仿真和模型计算结果对比,以无水乙醇介电实测值和理论值对比,验证模型的准确性。采用本文介电测量模型对不同含水率的黄绵土进行测量计算,复介电常数实部与实测土壤含水率二阶多项式拟合决定系数大于0.965,表明本文所提土壤介电测量方法适用于土壤复介电常数和含水率的测量。     

Sampling strategies for soil water content to estimate evapotranspiration

When the soil water balance method is applied at a field scale, estimation of the spatial variability and confidence interval of actual evapotranspiration is rare, although this method is sensitive to the spatial variability of the soil, and thus to the sampling strategy. This work evaluated the effect of soil sampling strategies for soil water content and water flux at the bottom of the soil profile on the estimation of the daily and cumulative evapotranspirations. To do that, according to the statistical properties of daily measurements in a field experiment with a soybean crop, the water content and flux through the base to the soil profile in space (field scale) and time (daily scale) were simulated. Four different sampling strategies were then compared, and their effects on daily and seasonal cumulative evapotranspirations quantified. Strategy 1 used ten theoretical sites randomly located in the field. The daily water content estimates were assumed to be available each day from these same ten locations, which were located from 0.15 m to 1.55 m in depth, with space steps of 0.10 m. Strategy 2 assumed that daily water content estimates combined two sources: in the 0.00–0.20 m soil layer, ten theoretical sites were selected but changed every day, with thin soil layers for soil moisture sampling, from 1 to 5 cm in thickness. In the 0.20–1.60 m soil layer, the daily water content estimates were assumed to come from the same ten locations (the first soil moisture estimate was located at 0.25 m, and the others were located every 0.10 m until 1.55 m). Strategy 3 used ten theoretical sites located in the field, as in strategy 1, however the water content estimates in the 0.00–0.20-m soil layer were assumed to come from accurate water content measurements (soil layers from 1 to 5 cm in thickness), while for the 0.20–1.60 m soil layer, the strategy was similar to strategies 1 and 2. Strategy 4 used 10 new theoretical locations of measurement every day. Precise water content estimates for thin layers were assumed to be available in the 0.00–0.20 m soil layer as in strategy 2. The layers for water content estimates in the 0.20–1.60 m were similar to those of strategies 1, 2, and 3. Results showed that the spatial variability of the daily actual evapotranspiration may not be negligible, and differences from approximately ±1.0 mm d ^–1 to ±3.0 mm d ^–1 were calculated between the four sampling strategies. Strategy 1 gave the worst results, because variations in the water content of the top soil layers were neglected, and thus the daily evapotranspiration was underestimated. Strategy 2 led to a considerable variability for estimating daily evapotranspiration which was explained by the effect of the spatial variability due to the daily site sampling for the top soil layers (0 to 0.2 m). Strategy 3 appeared to be the best practical compromise between practical field considerations and the necessity to obtain accurate evapotranspiration measurements. The accuracy of daily evapotranspiration could reach ± 0.5 mm d^–1, and could be further improved by increasing the number of measurement sites. The best results were obtained with strategy 4, although such a destructive and time-consuming strategy is not likely to be practical.     

Effect of soil moisture regimes on the yield and water use of lentil (Lens culinaris Medic)

Summary The effect of soil moisture regimes on the grain and straw yield, consumptive water use (Cu) and its relation with evaporation from free water surface (Eo), water use efficiency and soil moisture extraction pattern of lentil was studied in a field experiment conducted at the Indian Agricultural Research Institute, New Delhi during the fall-spring season of the crop years 1979–1980 and 1980–1981. The grain and straw yield, consumptive water use rate, Cu/Eo ratio and water use efficiency increased with an increase in irrigation frequency. Consumptive water use rate increased as the crop season advanced and reached its peak value during flowering and grain filling stage. The Cu/Eo ratio attained its minimum values 35 and 105 days after sowing at branching and grain filling stages. Depletion of soil moisture was most from the top 0–30 cm soil layer followed by 30–60 cm soil layer and was least from 90–120 cm soil layer. The pattern of soil moisture depletion was also influenced by soil moisture regime. During the vegetative and flowering stage the percent contribution from the top 0–30 cm soil layer decreased and that from the lower soil layers (30–60, 60–90, and 90–120 cm) increased with an increase in the soil moisture tension, however, the actual amount of moisture depleted from all the soil layers was always higher under low soil moisture tension regime than under high soil moisture tension regime. During the grain development stage the soil moisture treatment had no significant effect on the relative contribution from different soil layers under low and high soil moisture tension as the crop was irrigated at the same time under both these treatments. However, with no irrigation, the percent contribution from top soil layer continued to decrease, and from lower soil layers continued to increase, as the crop advanced from flowering stage to grain development stage.     

Evaluation of time domain reflectometry (TDR) for estimating furrow infiltration

TDR was used to estimate furrow infiltration, which is a key component in furrow irrigation system design and management. Furrow irrigation experiments were conducted on bare and cropped fields consisting of three 40 m long parabolic shaped furrows spaced at 0.8 m on a slope of 0.5%. The centre furrow was taken as the study furrow and the other two provided a buffer to the centre furrow. Altogether, 22 irrigations were conducted during 2004 and 2005 with inflow rates ranging from 0.1 to 0.7 l s⁻¹. TDR probes were installed vertically around the centre furrow at four locations 0.5 (S₁), 13 (S₂), 26 (S₃) and 39.5 m (S₄) from the inlet end. The S₁ and S₃ locations had four TDR probes installed at 0.15, 0.30, 0.45 and 0.60 m depths whereas the S₂ and S₄ locations had two probes each at 0.15 and 0.30 m depths. Soil moisture data collected at 5-min intervals were used to determine the average soil moisture content of the field. The change in moisture content was used to estimate the furrow infiltration which was compared with that measured using an inflow–outflow (IO) method. The performance of the TDR method was studied by calculating the absolute prediction error (APE), root mean square error (RMSE) and index of agreement (I _a). It was found that the TDR-method estimated furrow infiltration well for higher inflow rates and during the initial stages of irrigation. APE decreased and I _a increased with increase in flow rate for both bare and cropped conditions. The APE and RMSE were found to be larger for a cropped field than the bare field when irrigated at the same inflow rate. The accuracy of the TDR-method for estimating total infiltration was improved by using the average field moisture content of 30 or 45 min after the recession phase ceased. These results indicate that TDR can be used to estimate in situ infiltration under furrow irrigation.     

A model for equitable distribution of canal water

The equitable distribution of canal water is imperative to ensure social justice as well as crop productivity. In north-west India and Pakistan, water from the tertiary canal (watercourse) is distributed to the farmers through a rotational system of irrigation. In this system the duration of supply to each farmer is in proportion to his holding in the outlet (watercourse) command, without considering the seepage loss. The rate of seepage loss increases with increase in length of watercourse from head to tail. Thus, the farmers in the lower reaches get much less water per unit area than the farmers in the upper reaches. The farmers must be compensated for the seepage loss. Therefore, a model was developed to ensure equitable distribution of water to the farmers located on a watercourse in proportion to their land holdings giving due compensation for the seepage loss. The model is based on the assumption that soil throughout the length of flow is homogeneous and loss through evaporation is negligible. The model developed ensures an equitable distribution of water to the farmers according to their land holdings. A comparison of existing and revised time allocation reveals that the farmers located in the upper reaches were getting more time (up to 12.2 min per unit area), while the farmers located in the lower reaches have been getting less time (up to 28.1 min per unit area). The existing allocation of time of 0.75 h per unit area to all the farmers according to the old rules was revised to 0.546–1.219 h per unit area from head to tail. The conclusions drawn suggest that the strategy developed here should be adopted elsewhere in the existing system of irrigation for equitable distribution of canal water. Received: 21 December 1999     

智能滴灌系统中土壤水分传感器埋设深度研究

智能滴灌系统顺应了我国水资源高效利用的要求,实现了作物的精确、适时灌溉,同时也为土壤水分状况的测量提出了更高的要求。土壤水分传感器恰好满足这个要求,其埋设深度是实现智能滴灌控制系统所需解决的最主要问题之一。通过对黄瓜根系分布特征和滴灌条件下黄瓜根区土壤含水率的变化规律的分析,初步给出了传感器在黄瓜根区的2种埋设方案。在垂直方向以地表以下5～10、20～30 cm处为埋设传感器的最佳深度,40～50 cm处为辅助埋设深度。     

Irrigation and drainage needs of transplanted rice in diked rice fields of rainfed medium lands

An experiment was conducted in diked rice fields with various weir heights (6 cm to 30 cm at an interval of 4 cm) for three consecutive years in the sub-humid climate of eastern India. The results reveal that about 56.75% and 99.5% of the seasonal rainfall can be stored in 6 cm and 30 cm weir height plots, respectively. Sediment losses of 347.8 kg/ha and 3.3 kg/ha have been recorded in runoff water coming out of 6 cm and 30 cm weir height plots, respectively in a cropping season. Similarly, total Kjeldahl nitrogen loss in runoff water from rice fields ranged from 4.23 kg/ha (6 cm weir height plots) to 0.17 kg/ha (26 cm weir height plots). The available K loss ranged from 2.20 kg/ha (6 cm weir height plots) to 0.04 kg/ha (30 cm weir height plots). Keeping in mind the aspects of conserving rainwater, sediment and nutrient and minimizing irrigation requirement, 22–26 cm of dike height is considered to be suitable for rice fields of the Bhubaneswar region during the Kharif (rainy) season. A lumped water balance model for diked rice field was developed and used for the present investigation. The computed values of runoff obtained from the simulation model are in close agreement with the observed values obtained in an experiment using higher weir heights (22 cm and above). The temporal distribution of runoff and irrigation requirement at fortnight intervals reveal that highest irrigation requirement is found during the first half of November followed by the second half of October and the first half of October. Rice fields up to a weir height of 18 cm produced about 20% of the total runoff in each of the first three fortnights. A gradual reduction in runoff was observed in the remaining fortnights. The least runoff was noticed in the month of November (during the first fortnight).     

Multi-wire time domain reflectometry (TDR) probe with electrical impedance discontinuities for measuring water content distribution

The adequate estimation of water content distribution in wetted volume is fundamental in determining the number of drippers per plant and their location below the plant canopy in drip irrigation. Measurements of water content distribution are usually made by opening trenches, which is a time-consuming method and sometimes imprecise. Recent scientific developments have created the possibility of monitoring the soil moisture content using electronic sensors. The objective of this research was to develop and test two multi-wire time domain reflectometry (TDR) probes with electrical impedance discontinuities (referred to as the multi-wire probe) for sensing soil profile water content distribution. The experiment was divided in two parts. In part one, the laboratory performance of two multi-wire probe designs was studied and their reliability to monitor the water content variation in a porous media profile was evaluated. The second part was conducted in a 250 l bucket and the soil water content distribution, for an application depth of 15 mm, was evaluated by monitoring over 6 days at discharge rates of 2 and 4 l h⁻¹. The results demonstrated the viability of using multi-wire probes to estimate soil water content distribution with different probe designs and to consistently obtain water content measurement in water dynamic processes. The following conclusion may drawn from the main results: (1) The measured characteristic impedance of the multi-wire probe for different designs was not the same as that geometrically calculated. This was due to the non-ideal probe geometry which provoked signal loss, thus, hindering peak impedance interpretation, mainly for probe 1 design. (2) The use of multi-wire probes in the TDR equipment showed a speedy determination of soil profile water content distribution using a single measurement.     

一种土壤水分传感器性能测试的方法及应用

针对目前土壤水分传感器室内标定时很难得到含水率均匀的土样,设计了一种试验装置和测试方法。通过一系列室内试验,对3种土壤水分传感器进行了测试和标定。结果证明,这种方法对于短探针土壤水分传感器的标定切实可用,同一种传感器在不同质地土壤中标定曲线不同,给出了3种传感器在砂土、壤土、粘土中的标定曲线,并分别从线性度、敏感度、稳定性等方面对3种土壤水分传感器进行了分析比较。     

西北枣林土壤水分自然修复及其模拟

以节水型修剪下矮化密植枣树为研究对象,设置4种不同初始土壤含水率,在雨养条件下连续2 a观测土壤水分、生物量,结合HYDRUS 1D模型分析评价了林地水分修复。结果表明,自然降雨条件下,4个小区土壤水分趋向一个稳定值,该值大小取决于当年降雨量。基于HYDRUS 1D模拟的枣园土壤水分相对误差为1.52%,均方根误差未超过0.5,决定系数平均达94%,说明该模型在该地区具有较好的适用性。HYDRUS 1D模拟节水型修剪下的枣林土壤水分显示在今后60 a可以保持多数年土壤水分处于良好水平。