Analysis of AET and yield predictions under surface and buried drip irrigation systems using the Crop Model PILOTE and Hydrus-2D

Innovative irrigation solutions have to face water scarcity problems affecting the Mediterranean countries. Generally, surface (DI) or subsurface drip irrigation systems (SDI) have the ability to increase water productivity (WP). But the question about their possible utilisation for crops such as corn would merit to be analysed using an appropriate economic tool. The latter would be necessary based on the utilisation of a modelling approach to identify the optimal irrigation strategy associating a water amount with a crop yield (Yc). In this perspective, a possible utilisation of the operative 1D crop model PILOTE for simulating actual evapotranspiration (AET) and yield under a 2D soil water transfer process characterizing DI and SDI was analysed. In this study, limited to a loamy soil cultivated with corn, the pertinence of the root water uptake model used in the numerical code Hydrus-2D for AET estimations of actual evapotranspiration (AET) under water stress conditions is discussed throughout the Yc = F(AET) relationship established by PILOTE on the basis of validated simulations. The conclusions of this work are (i): with slight adaptations, PILOTE can provide reliable WP estimations associated to irrigation strategies under DI and SDI, (ii): the current Hydrus-2D version used in this study underestimates AET, compared with PILOTE, in a range varying from 7% under moderate water stress conditions to 14% under severe ones, (iii): A lateral spacing of 1.6 m for the irrigation of corn with a SDI system is an appropriate solution on a loamy soil under a Mediterranean climate.A local Yc = F(AET) relationship associated with a Hydrus-2D version taking into account the compensating root uptake process could result in an interesting tool to help identify the optimal irrigation system design under different soil conditions.     

Effect of temporal variability in soil hydraulic properties on simulated water transfer under high-frequency drip irrigation

The effect of changes in the hydraulic properties of a loamy topsoil on water transfer under daily drip irrigation was studied over a cropping cycle. Soil water contents were measured continuously with neutron probes and capacitance sensors placed in access tubes (EnviroSMART) and were compared to predications made by the Hydrus-2D model. Three different sets of hydraulic parameters measured before and after irrigation started, were used.Our results demonstrated that, based on the assumptions used in this study, the accuracy of the Hydrus predictions is good. Graphical and statistical comparisons of simulated and measured soil water contents and consequently the total water storage revealed a similar trend throughout the monitoring period for the all three different sets of parameters. The soil hydraulic properties determined after irrigation started were found to be much more representative of the majority of the irrigation season, as confirmed by the accuracy of the simulation results with high values of the index of agreement and with values of RMSE similar in magnitude to the error associated with field measurements (0.020 cm³ cm⁻³). The highest RMSE values (about 0.04 cm³ cm⁻³) were found when the model used input soil parameters measured before irrigation started.Generally, changes in topsoil hydraulic properties over time had no significant effect on soil moisture distribution in our agro-pedo-climatic context. One possible explanation is that daily water application was conducted at the same time as maximal root water uptake. This meant the soil did not need to store total daily crop water requirements and consequently that the water redistribution phase represented a very short stage in the irrigation cycle. It is probable that irrigating in the daytime when crop evapotranspiration is highest could prevent the effects of a temporal change and other problems connected with the soil. Moreover, water will be always available for the crop. Further experiments are needed to justify the results and to study the effects of low frequency drip irrigation on soil hydraulic characterization and consequently on soil water transfer in order to improve irrigation scheduling practices.     

地下滴灌中毛管水力计算的数学模型与试验

为了研究地下滴灌毛管水力特性与水力计算方法,用较短毛管并通过毛管末端泄流的方式,在室内利用地下滴灌毛管水力要素试验测试系统,分别测试了2种滴灌管在轻黏土中毛管上每个滴头的流量和毛管首末两端的压力水头．结果表明：在灌水持续2min之后,地下滴灌毛管上各滴头流量均趋于恒定值;在稳定的压力水头差下,滴头流量沿程依次减少．根据毛管沿程压力变化规律,结合考虑土壤质地、土壤体积质量和初始含水率的地下滴灌滴头流量计算公式,提出了毛管水力计算数学模型．利用该模型计算的滴头流量值与其实测值之间的相对误差在1．0％左右;并计算出考虑毛管局部水头损失的加大系数约为1．20．将该模型推广应用于一般情况下的地下滴灌毛管水力计算,可求解均匀坡、均质土、均匀管径与滴头等间距时的地下滴灌毛管水力特征值．     

葡萄分层地下滴灌滴头布设深度优化

为解决不同树龄葡萄根系的差异使得地下滴灌系统在布设应用中存在的困难,采用室内试验和HYDRUS-2D数值模拟相结合的方法,以宁夏和关中葡萄产区为例,研究了2种土质条件下分层地下滴灌土壤水分运动规律,提出了分层地下滴灌带最佳布设深度.研究结果表明,HYDRUS-2D模拟值与试验实测值具有良好的吻合度.地下滴灌带的埋深直接影响土壤水分的分布,2种土质下湿润体内部处于最佳含水率区间的土壤体积随滴头间距的增加而增大.通过适当增大浅层滴头埋深并减小深层滴头埋深可减小表层水分无效损耗.从避免水分无效消耗以及提高湿润体与根系匹配效果等角度出发,建议关中地区葡萄单滴头灌溉且适宜滴灌带布设深度为20 cm;宁夏贺兰山地区滴灌带布设深度以15 cm和45 cm为宜.     

Salt distribution and the growth of cotton under different drip irrigation regimes in a saline area

A 3-year experiment was conducted in an extremely dry and saline wasteland to investigate the effects of the drip irrigation on salt distributions and the growth of cotton under different irrigation regimes in Xinjiang, Northwest China. The experiment included five treatments in which the soil matric potential (SMP) at 20 cm depth was controlled at −5, −10, −15, −20, and −25 kPa after cotton was established. The results indicated that a favorable low salinity zone existed in the root zone throughout the growing season when the SMP threshold was controlled below −25 kPa. When the SMP value decreased, the electrical conductivity of the saturation paste extract (EC_e) in the root zone after the growing season decreased as well. After the 3-year experiment, the seed-cotton yield had reached 84% of the average yield level for non-saline soil in the study region and the emergence rate was 78.1% when the SMP target value was controlled below −5 kPa. The average pH of the soil decreased slightly after 3 years of cultivation. The highest irrigation water use efficiency (IWUE) values were recorded when the SMP was around −20 kPa. After years of reclamation and utilization, the saline soil gradually changed to a moderately saline soil. The SMP of −5 kPa at a depth of 20 cm immediately under a drip emitter can be used as an indicator for cotton drip irrigation scheduling in saline areas in Xinjiang, Northwest China.     

Numerical simulations of water movement in a subsurface drip irrigation system under field and laboratory conditions using HYDRUS-2D

Due to the decreasing availability of water resources and the increasing competition for water between residential, industrial, and agricultural users, increasing irrigation efficiency, by methods like subsurface drip irrigation (SDI) systems, is a pressing concern for agricultural authorities. To properly manage SDI systems, and increase the efficiency of the water/fertilizer use while reducing water losses due to evaporation, the precise distribution of water around the emitters must be known. In this paper, the Windows-based computer software package HYDRUS-2D, which numerically simulates water, heat, and/or solute movement in two-dimensional, variably-saturated porous media, was used to evaluate the distribution of water around the emitter in a clay loam soil. The simulation results were compared with two sets of laboratory and field experiments involving SDI with emitters installed at different depths, and were evaluated using the root-mean-square-error (RMSE). The RMSE at different locations varied between 0.011 and 0.045 for volumetric water contents, and between 0.98 and 4.36 cm for wetting dimensions. Based on these values, it can be concluded that the correspondence between simulations and observations was very good.     

不同灌溉方式对降雨入渗深度的影响

为了研究不同灌溉方式对降雨入渗深度的影响,基于田间原位观测试验,分析膜下滴灌和传统地面灌溉2种方式对降雨入渗初始含水率的影响,并应用HYDRUS-2D模型模拟2种灌溉方式下不同降雨条件的入渗深度差异.结果表明:与传统地面灌溉方式相比,膜下滴灌改变了降雨入渗初始含水率,且在玉米不同的生育期,其对降雨入渗初始含水率的影响规律不同.通过不同情景的降雨入渗模拟得到,在初始条件完全相同的情况下,2种方式的降雨入渗深度主要受雨量和时间的影响,在降雨量较小时,膜下滴灌的入渗深度大于地面灌;随着降雨量及时间增加,2种灌溉方式下的入渗深度逐渐趋于一致.不论是玉米苗期阶段还是主要生长阶段,降雨入渗的土壤初始含水率均会对降雨入渗深度产生一定的影响:在玉米苗期阶段,膜下滴灌的入渗深度大于地面灌,而在玉米主要生长阶段,地面灌的入渗深度大于膜下滴灌.     

玉米地下滴灌适宜出苗灌水定额试验研究

为探索解决地下滴灌玉米出苗难的问题,通过土箱试验,对内蒙古自治区具有典型代表性的3种土壤,开展了毛管铺设参数(滴头流量、埋深)和灌水定额对地下滴灌湿润半径的影响规律试验,结合玉米播种深度、水分向上及向下运移的距离及种子周围土壤含水量,研究了玉米适宜出苗灌水定额,以提高出苗率,指导实际生产.结果表明:按显著性水平0.05检验,土壤类型和灌水定额均对土壤湿润半径影响具有统计学意义,而滴头流量和埋深对湿润半径影响不具有统计学意义.在黏壤土中,玉米出苗灌水定额37.5~52.5 mm基本可满足毛管埋深25~35 cm的出苗要求;在壤土中,玉米出苗灌水定额37.5 mm左右基本可满足毛管埋深25~30 cm的出苗要求,灌水定额52.5 mm左右基本可满足埋深30~35 cm的出苗要求;在砂壤土中,灌水定额22.5~37.5 mm基本可满足毛管埋深约25 cm的玉米出苗要求,灌水定额52.5 mm基本可满足毛管埋深25~35 cm的玉米出苗要求.     

河套灌区解放闸灌域盐荒地积盐量分析

以解放闸灌域为背景对盐荒地水分和盐分的变化展开研究.在田间试验的基础上,通过遥感技术对TM数据解译统计盐荒地面积,利用HYDRUS-1D模型对盐荒地土壤盐分的积聚量与流失量进行了模拟和分析.结果表明,盐分在表层土壤中积聚,解放闸灌域总面积为2 156.47 km²,盐荒地达到了总面积的16.32%.灌域盐荒地1 m深土壤层中,在作物生育期积聚盐量为10.32×10⁶ kg,在秋浇期流失盐量为9.60×10⁶ kg,占积盐量的93.01%;年度积盐量为0.72×10⁶ kg,占积盐量的6.99%.经检验,HYDRUS-1D模型对土壤水分和盐分在垂直方向运移的模拟具有较高精度,反映出盐分积聚和流失规律.盐荒地盐分的积聚与流失对灌区盐分具有重要调节作用,可为灌区水盐运移的研究提供科学依据.     

Drip irrigation water and salt flow model for table grapes in Coachella Valley,California

Unlike annual crops where reclamation leaching of salts can be readily conducted between cropping, leaching of salts in permanent crops that are drip irrigated pose challenges. A need exists to formulate and test a management-type of salinity model for drip irrigation of table grapes. The model reported herein predicts the distribution of salts along the vine row and between the rows during the growing season, as affected by reactivity of salts of the applied irrigation water as well as rate and duration of drip application. The calibrated model reproduced the initial field salinity profiles after repeated irrigation cycles by adjusting only the routing factor α which is the ratio of horizontal to vertical water flow. After eight cycles the profiles stabilized and the calibrated horizontal to vertical flow routing ratio was 0.6. There is remarkable agreement between measured and simulated salinity. Corresponding soil moisture profiles show the expected high water content with depth at the emitter, the decrease in surface water content with radial distance and the increase with depth, at the distal end of the wedge. Although the model is location specific it can be applied knowing soil, initial and boundary conditions, as well as irrigation application quantity and quality and as such can be applied location by location in order to assess flow and quality of deep percolation recharging the groundwater system. With this capacity the model can predict soil water quantity and quality outcomes for possible land and water management scenarios.     

Spatial root distribution of mature apple trees under drip irrigation system

The study was undertaken in order to quantify the effect of 12-year irrigation by drip emitters placed on one side of the tree trunk on the rooting pattern of Gloster apple trees (Malus domestica Borkh) grafted on M26 rootstock under the conditions of south-west Poland. The orchard was established in 1994 and since 1995 was drip irrigated under three treatments: V0 - without irrigation (control), V1 - intensive irrigation, and V2 - economical irrigation. In March 2007, after 12 years of irrigation, a profile trench observation method was used to map the number and the location of root distribution in clay loam (Luvisol) soil.The root system architecture was largely affected by irrigation. In case of the trees irrigated intensively (V1), the study showed asymmetry in the distribution of roots of diameter <1 mm and 1-3 mm. In V1, shallow root system, concentrated in the wetted zone developed on the irrigated side of the tree, where on the side of the tree trunk opposite the emitter trees developed significantly larger numbers of roots, which penetrated deeper soil layers. There were no statistically significant differences in the number of roots between both sides of the tree trunk under the treatment with economical irrigation (V2). Moreover, spatial roots distribution over the entire soil profile was found to be the most uniform compared to the other experimental treatments (V0 and V1). Finally, the study examined the relationship between root system and yield. Obtained results showed that in the 3-year period less frequent water application (V2) resulted in the highest yield.     

Effect of irrigation amounts applied with subsurface drip irrigation on corn evapotranspiration, yield, water use efficiency, and dry matter production in a semiarid climate

Quantifying the local crop response to irrigation is important for establishing adequate irrigation management strategies. This study evaluated the effect of irrigation applied with subsurface drip irrigation on field corn (Zea mays L.) evapotranspiration (ETc), yield, water use efficiencies (WUE = yield/ETc, and IWUE = yield/irrigation), and dry matter production in the semiarid climate of west central Nebraska. Eight treatments were imposed with irrigation amounts ranging from 53 to 356 mm in 2005 and from 22 to 226 mm in 2006. A soil water balance approach (based on FAO-56) was used to estimate daily soil water and ETc. Treatments resulted in seasonal ETc of 580–663 mm and 466–656 mm in 2005 and 2006, respectively. Yields among treatments differed by as much as 22% in 2005 and 52% in 2006. In both seasons, irrigation significantly affected yields, which increased with irrigation up to a point where irrigation became excessive. Distinct relationships were obtained each season. Yields increased linearly with seasonal ETc (R² = 0.89) and ETc/ETp (R² = 0.87) (ETp = ETc with no water stress). The yield response factor (ky), which indicates the relative reduction in yield to relative reduction in ETc, averaged 1.58 over the two seasons. WUE increased non-linearly with seasonal ETc and with yield. WUE was more sensitive to irrigation during the drier 2006 season, compared with 2005. Both seasons, IWUE decreased sharply with irrigation. Irrigation significantly affected dry matter production and partitioning into the different plant components (grain, cob, and stover). On average, the grain accounted for the majority of the above-ground plant dry mass (≈59%), followed by the stover (≈33%) and the cob (≈8%). The dry mass of the plant and that of each plant component tended to increase with seasonal ETc. The good relationships obtained in the study between crop performance indicators and seasonal ETc demonstrate that accurate estimates of ETc on a daily and seasonal basis can be valuable for making tactical in-season irrigation management decisions and for strategic irrigation planning and management.     

膜下滴灌结合暗管排水技术改良新疆盐碱地效果综述

膜下滴灌技术的大面积推广和应用,为新疆乃至西北干旱地区作物高产提供了强大的技术支撑。应用在盐碱地改良中,膜下滴灌“有灌无排”模式仅调节耕层盐分分布,并不能将盐分排出土体,长年灌溉容易引起爆发式积盐的风险,而暗管排水是目前公认的改良盐碱地最直接、最有效的方法。目前,将膜下滴灌与暗管排水有机结合形成的新型灌溉技术,充分利用膜下滴灌良好的抑蒸增温、节水抑盐等优势,同时利用暗管将淋洗盐水及时排出土体,使盐碱化土层产生新的水盐平衡,已在新疆盐碱地区开发利用中得到长足发展。本文重点分析并总结了新疆灌区膜下滴灌结合暗管排水系统的设计参数及土壤水盐运移规律,并综述了土壤理化性质及作物产量对该灌排技术的响应研究,以期为新疆盐碱地农业可持续发展提供理论依据和技术指导。     

The effect of drip line spacing, irrigation regimes and planting geometries of tomato on yield, irrigation water use efficiency and net return

This study was conducted in order to determine the effect of drip line spacing, irrigation regimes and planting geometries of tomato on yield, irrigation water use efficiency (IWUE) and net return. The experiments were carried out in the conditions of Eskisehir in Central Anatolian part of Turkey, between 2003 and 2005, with cv. Dual Large F1 tomatoes (Lycopercion esculentum L). The maximum yield of 121.1 t ha⁻¹ was obtained from the treatment in which both the lateral and row spacing were 1 m, and irrigated with water amount based on the percentage of canopy cover. The seasonal irrigation water amount of the treatment was 551 mm. Tomatoes yield of 109.9 t ha⁻¹ was obtained under conditions of 491 mm seasonal irrigation water applied for the 2-m lateral spacing in which two plant rows (twin rows) were planted 0.35 m on either side of the lateral with a row spacing of 0.70 m across the drip lateral and 1.30 m in the interrow between each set of twin rows. Although water saving of 60 mm and investments economy of 40% were provided from the twin-row design, the yearly return of the design including one lateral for each row was US$ 1590 ha⁻¹ higher than that the return of the twin-row design. The method of determination of irrigation water amount based on the percentage of canopy cover appeared to be the most reasonable and effective one in terms of the yield and IWUE. On the other hand, the maximum irrigation water use efficiency (22.3 kg m³) was obtained from 2-m lateral spacing and the percentage of canopy cover for calculation of the amount of irrigation water applied. Thus, canopy cover may be used successfully at any lateral design conditions.     

循环曝气地下滴灌的温室番茄生长与品质

循环曝气滴灌可以大幅度提高灌溉水掺气比例,有效改善普通地下滴灌引起的黏质型土壤根区间歇性缺氧环境,提高作物生产力.以河南省中牟县黄河淤积黄黏土为供试土壤,以温室番茄为供试对象,研究循环曝气地下滴灌对番茄生理及品质的影响.结果表明,与普通地下滴灌(对照处理)相比,相同灌溉定额条件下曝气处理番茄果实前5次产量提高了29.15%;番茄的水分利用效率提高了20.72%.曝气处理气孔导度提高了30.51%,植物的生长活力得到增强.番茄果实维生素C含量提高了13.25%,可溶性固形物含量提高了8.62%,糖酸比提高了22.05%,而总酸含量和硬度分别下降了15.50%和11.19%.曝气处理最大根长增加了16.75%,根冠质量之比提高了25.81%.综合分析表明,曝气滴灌可显著促进黄黏土中番茄的生长,促进番茄果实成熟,有效提高作物产量,改善番茄品质.     

Effect of saline water on cucumber (Cucumis sativus L.) yield and water use under drip irrigation in North China

Saline water has been included as an important substitutable resource for fresh water in agricultural irrigation in many fresh water scarce regions. In order to make good use of saline water for agricultural irrigation in North China, a semi-humid area, a 3-year field experiment was carried out to study the possibility of using saline water for supplement irrigation of cucumber. Saline water was applied via mulched drip irrigation. The average electrical conductivity of irrigation water (EC_iw) was 1.1, 2.2, 2.9, 3.5 and 4.2 dS/m in 2003 and 2004, and 1.1, 2.2, 3.5, 4.2 and 4.9 dS/m in 2005. Throughout cucumber-growing season, the soil matric potential at 0.2 m depth immediately under drip emitter was kept higher than −20 kPa and saline water was applied after cucumber seedling stage. The experimental results revealed that cucumber fruit number per plant and yield decreased by 5.7% per unit increase in EC_iw. The maximum yield loss was around 25% for EC_iw of 4.9 dS/m, compared with 1.1 dS/m. Cucumber seasonal accumulative water use decreased linearly over the range of 1.5-6.9% per unit increase in EC_iw. As to the average root zone EC_e (electrical conductivity of saturated paste extract), cucumber yield and water use decreased by 10.8 and 10.3% for each unit of EC_e increase in the root zone (within 40 cm away from emitter and 40 cm depths), respectively. After 3 years irrigation with saline water, there was no obvious tendency for EC_e to increase in the soil profile of 0-90 cm depths. So in North China, or similar semi-humid area, when there is no enough fresh water for irrigation, saline water up to 4.9 dS/m can be used to irrigate field culture cucumbers at the expense of some yield loss.     

Economic feasibility of growing capsicum crop under drip irrigation in West Bengal, India

Drip irrigation system has been one of the technical means to improve water use efficiency. In India, this system is gaining popularity among fruit growers and in water scarced area but a substantial area is being covered annually under vegetables crops. One of the major concerns raised by farmers about this system is its economic viability. In present study, the economic viability of drip irrigation system for growing capsicum crop based on discounted cash flow technique (Net present worth and Benefit cost ratio) was explored. Eight irrigation treatments were laid under drip with and without plastic mulch. The irrigation levels were taken as 1, 0.8 and 0.6 of the crop evapotranspiration. The pan evaporation method was used for estimation of reference evapotranspiration and Water Balance Approach was used for irrigation scheduling. The average amount of water supplied under treatment VD (100% irrigation requirement supplied with drip) was found to be 415 mm for whole growing season of the crop. Similarly the amount of water was found to be 332 mm and 249 mm for the treatment 0.8VD (80% irrigation requirement supplied with drip) and 0.6VD (60% irrigation requirement supplied with drip) respectively. Highest yield was recorded in case of treatment VD + PM (100% irrigation requirement supplied with drip plus plastic mulch) followed by VD. Yield under treatments 0.8VD, 0.6VD, 0.8VD + PM and 0.6VD + PM were significant while treatments VD, VF and VF + PM were at par with the treatment VD + PM. Net Present Worth (NPW) was found to be positive for all the treatments. The highest NPW was obtained under treatment VD as Rs. 309,734.90 and lowest was in case of 0.6VD + PM as Rs. 144,172.24. The yield per mm of water used was reported to be at higher side as 35 in both the treatments VD and VD + PM. But the yield per mm of water used was found to be lowest as 18.07 and 19 in case of VF and VF + PM respectively.     

Water balance of apricot trees (Prunus armeniaca L. cv. Búlida) under drip irrigation

The water balance of drip irrigated apricot trees (Prunus armeniaca L. cv. Búlida grafted onto “Realfino” apricot rootstock) was determined during a 30-month-period. Two irrigation regimes based on the reduction coefficients of Class A pan evaporation (1 and 0.5) were used to determine the water consumed. The water balance parameters for these treatments are shown and discussed in detail. Overall, the trees receiving less water showed 35% less evapotranspiration. Crop coefficients calculated on the basis of the water balance over a 30-month-period led to a saving of almost 14% water, since the coefficients were slightly below those used in other apricot orchards in the same area.     

不同降水年型地下滴灌追氮对玉米产量的影响

采用完全组合设计,在长期试验基础上探讨了枯、丰2种降水年型滴灌追氮对玉米产量的影响.结果表明:丰水年整体产量高于枯水年,高水高氮和高水低氮处理在丰、枯水年间产量差异不具有统计学意义.枯水年滴灌对产量影响具有统计学意义(P<0.01),水氮互作对产量影响具有统计学意义(P<0.05),追氮对产量影响不具有统计学意义.丰水年滴灌对产量影响具有统计学意义(P<0.05),追氮对产量影响具有统计学意义(P<0.01),水氮互作对产量影响不具有统计学意义.不同降水年型间产量随滴灌量的增大而增大,枯水年滴灌对产量的提高幅度大于丰水年;随追氮量的增加先增大后减小,丰水年增加追氮量对产量的影响均大于枯水年.通过分析,确定了不同降水年型适宜的水肥施用模式:播种期沟施复合肥(N∶P₂O₅∶K₂O=15∶15∶15)450 kg/hm²后,在枯水年滴灌48 mm、追氮120 kg/hm²,丰水年滴灌36 mm、追氮240 kg/hm².     

Effect of soil matric potential on tomato yield and water use under drip irrigation condition

Field experiment was carried out to investigate the effect of soil matric potential (SMP) on tomato yield, evapotranspiration (ET), water use efficiency (WUE) and irrigation water use efficiency (IWUE) under drip irrigation condition in North China Plain. The experiment included five treatments, which controlled SMP at 0.2 m depth immediately under drip emitter higher than −10 (S1), −20 (S2), −30 (S3), −40 (S4) and −50 kPa (S5), respectively, after tomato plant establishment. The results showed that different SMP affected irrigation amount and tomato ET. Irrigation amount decreased from 185 mm (S1) to 83.6 mm (S5) in 2004, and from 165 mm (S1) to 109 mm (S5) in 2005, respectively. The ET decreased from 270 mm (S1) to 202 mm (S5) in both years. However, it was found that SMP did not affect the tomato yield significantly, for the range of SMP investigated. Both WUE and IWUE increased as SMP decreased. The maximum WUE (253 and 217 kg/ha mm) and IWUE (620 and 406 kg/ha mm) were for S5 in 2 years, whereas the minimum WUE (178 and 155 kg/ha mm) and IWUE 261 and 259 kg/ha mm) were for S1 in 2004 and 2005. Based on the above results, therefore, it is recommended that if the tomatoes are well irrigated (SMP is higher than −20 kPa) during establishment, controlling SMP higher than −50 kPa at 0.2 m depth immediately under drip emitter can be used as an indicator for drip irrigation scheduling during following period of tomato growth in North China Plain.