Evaluation of surface irrigation as a function of water infiltration in cultivated soils in the Nile Delta

As sources of irrigation water are decreasing, efficient use of surface irrigation is essential. The purpose of this study is to determine if partially-wetted furrow irrigation has more efficient water storage and infiltration than traditional border irrigation in an alluvial clay soil under cultivated grape production. The two irrigation components considered were wet (WT) and dry (DT) treatments, at which water was applied when available soil water reached 65 % and 50 %, and the traditional border irrigation control. Empirical power form equations were obtained for measured advance and recession times along the furrow length during the irrigation stages of advance, storage, depletion and recession. Coefficient of variation (CV) was 5.2 and 9.5 % for WT and DT under furrow irrigation system comparing with 7.8 % in border, respectively. Water was deeply percolated as 11.9 and 19.2 % for wet and dry furrow treatments respectively, compared with 12.8 % for control, with no deficit in the irrigated area. Partially-wetted furrow irrigation had greater water-efficiency and grape yield than dry furrow and traditional border irrigation, where application efficiency achieved as 88.1 % for wet furrow irrigation that achieved high grape fruit yield (30.71 Mg /ha). The infiltration (cumulative depth, Z and rate, I) was functioned to opportunity time (t ₀ ) in minute for WT and DT treatments as: Z _WT ?=?0.528?t ₀ ^0.6, Z _DT ?=?1.2?t ₀ ^0.501, I _WT ?=?19?t ₀ ^?0.4, I _DT ?=?36?t ₀ ^?0.498. Empirical power form equations were obtained for measured advance and recession times along the furrow length during the irrigation stages of advance, storage, depletion and recession. The irrigation parameters and coefficients, and soil water distribution have been also evaluated.     

Effects of water infiltration and storage in cultivated soil on surface irrigation

Surface irrigation analysis and design require the knowledge of the variation of the cumulative infiltration water Z (L) (per unit area) into the soil as a function of the infiltration time t (T). The purpose of this study is to evaluate water infiltration and storage under surface irrigation in an alluvial clay soil cultivated with grape yield, and to determine if partially wetted furrow irrigation has more efficient water storage and infiltration than traditional border irrigation. The two irrigation components considered were wet (WT) and dry (DT) treatments, at which water applied when available soil water reached 65% and 50%, and the traditional border irrigation control. Empirical power form equations were obtained for measured advance and recession times along the furrow length during the irrigation stages of advance, storage, depletion and recession. The infiltration (cumulative depth, Z and rate, I) was functioned to opportunity time (t_o) in minute for WT and DT treatments as: Z_WT = 0.528 t_o^0.6, Z_DT = 1.2 t_o^0.501, I_WT = 19 t_o^−0.4, and I_DT = 36 t_o^−0.498. The irrigation efficiency and soil water distribution have been evaluated using linear distribution and relative schedule depth. Coefficient of variation (CV) was 5.2 and 9.5% for WT and DT under furrow irrigation system comparing with 7.8% in border, respectively. Water was deeply percolated as 11.88 and 19.2% for wet and dry furrow treatments, respectively, compared with 12.8% for control, with no deficit in the irrigated area. Partially wetted furrow irrigation had greater water-efficiency and grape yield than both dry furrow and traditional border irrigations, where application efficiency achieved as 88.1% for wet furrow irrigation that achieved high grape fruit yield (30.71 Mg/ha) and water use efficiency 11.9 kg/m³.     

Stochastic modeling of basins microtopography: analysis of spatial variability and model testing

Microtopography is among the most important factors affecting the performance of basin irrigation system due to its influence on the advance and recession processes. This study is based on field-measured surface elevation of 116 basins in North China. The spatial variability of basins microtopography was analyzed using geostatistics; the spatial structure of basins microtopography can be characterized by a spherical semivariogram model. The correlations between selected basin geometry parameters, mainly the standard deviation (S _d ) of surface elevation differences (SED), and the semivariogram parameters were calculated and allow estimating the semivariogram parameters from basin characteristics. Considering the randomness of SED and, simultaneously, its spatial dependence, a procedure was developed to model the spatial distribution of SED using Monte-Carlo generation and kriging interpolation techniques. The required number of SED generations was also estimated depending upon the S _d of SED. The SED stochastic generation model was tested by comparing the advance, recession, flow water depths and performance parameters observed in an experimental basin with those simulated using measured and model generated SED data. Results show that estimation errors from using generated data are similar to those resulting from observations. Thus, SED generated data may be used for assessing the impacts of microtopography on irrigation performance.     

土壤入渗特性和田面糙率的变异性对沟灌性能的影响

以杨凌区粘壤土和砂壤土区域进行的大田沟灌试验为基础,在假定各灌水沟内部土壤入渗特性和糙率均一的条件下,重点分析各灌水沟之间土壤入渗参数和田面糙率的不同组合对沟灌水流运动过程和灌水质量的影响,结果表明土壤入渗特性的变异性对沟灌水流推进过程和灌水质量指标影响较大,在模拟时必须充分考虑;而田面糙率的变异性对沟灌水流推进过程和灌水质量指标影响较小,可采用田块糙率均值代替各灌水沟的糙率。经实例验证,水流推进过程相对误差为7.28%,灌水效率、灌水均匀度和储水效率模拟值与实测值误差分别为5.74%、6.18%和4.07%,结果表明其模拟效果较好。     

环式入渗仪测量土壤初始入渗率效果试验

提出一种环式入渗试验装置,可以在入渗进行一段时间后,通过观测初始入渗水在土壤剖面的分布,估量初始入渗的过程。该入渗环为可拆分的两个半环,以便通过观察入渗水分在土壤剖面的分布估计初始入渗特性。论述了环的构成和测量过程与方法。同时用有机玻璃圆管装填土样,对比观察模拟真实一维入渗过程。用采自北京的粉壤土和该试验装置进行土壤入渗试验。试验分为3种入土打击能量:1、2、4 kg铁锤,自1 m高处自由落体打击入渗环入土。土壤干体积容积密度分别为:1.2、1.3、1.4 g/cm3。每次试验均向环内注入2 L水,每组试验进行2次重复。入渗环内土壤湿润土体表明,实际发生的土壤入渗为由环壁向环内土壤的径向入渗和由地表向下垂直入渗构成,环壁与土壤剖面间产生的优先流极大地影响了初始土壤入渗率的测量精度。在初始入渗阶段,由环壁向土体的水平径向入渗宽度和由地表向土体的垂直入渗深度近似相等,垂直入渗深度是水平径向入渗宽度的1.001倍。环式入渗仪测得的土壤初始入渗率为模拟真实一维入渗率的3.3倍。研究结果可为环式入渗仪测量结果的评估提供参考。     

Evaluating infiltration for border irrigation models

The infiltration characteristics of a soil are important to the design, evaluation and management of border irrigation systems. The use and verification of border irrigation models also rely heavily on infiltration. This paper presents a technique for determining infiltration when detailed information is available on the total infiltrated volume during the irrigation which can be obtained from measurements of inflow, outflow, and water depths on the border strip. The method uses a volume balance at progressive times and is an extension of earlier work. Data from this method were used as input to the zone-inertia border irrigation model and good agreement was found between measured and computed values of advance, recession, runoff rates and volumes, and surface water depths.     

Evaluation of infiltration measurements for border irrigation

A number of methods are discussed for obtaining a reasonable estimate of the infiltration function for irrigation borders. Data from ring infiltrometers are fit to power functions for infiltration rate and cumulative infiltration rate versus time and to a branch function where the infiltration rate is not allowed to go below some value (called the final infiltration rate). A volume balance within the border is used to adjust the data to give a better indication of the “average” infiltration conditions over the border. The results of Bouwer's method, which uses a series of borders as infiltrometers, were compared to the results of ring data for actual field data. Bower's method was also analyzed by developing advance and recession curves with the zero-inertia border-irrigation model with a known infiltration rate. The zero-inertia model was also used to examine the effect of different infiltration functions for specific examples (resulting from different irrigations or different estimation methods) on the application of water by surface irrigation.     

Infiltration rate measurements in arid soils with surface crust

The effects of infiltrometer type and water application rate on infiltration were studied for a crust-forming soil at the University of Jordan Research Station near Al-Muwaqqar village. The total amount of water applied in all cases was 38 mm. The highest infiltration rate values occurred in basin infiltrometers followed by sprinkler and furrow infiltrometers. The infiltration rate at the end of water application decreased significantly by 41–57% with decreasing application rate from 28.4 to 6.2 mm/h regardless of infiltrometer type. Increasing the initial soil moisture content decreased the infiltration rate by about 4–11% in all infiltrometer types and application rates. In the basin infiltrometer, lateral water movement occurred all around the basin borders, thus increasing the measured basic infiltration rate. In the furrow infiltrometer, the formation of a sedimentary crust on the furrow bottom reduced the basic water infiltration rate to 3.6 mm/h. The wetted zone formed with the sprinkler infiltrometer reduced lateral water movement, and the measured basic infiltration rate was close to the basic infiltration rate measured by the double-ring infiltrometer. The measurements were used to establish infiltration rate curves and equations. In a second experiment, the Stirk correction significantly reduced the water lateral divergence factor by 27.1% in single-ring infiltrometers. The Stirk correction factor was different in single- and double-ring infiltrometers. Thus, the basic infiltration rate was 4.8 and 3.5 mm/h using the single and the double infiltrometers, respectively, while the corresponding correction factors were 0.67 and 0.91, respectively. The corrected infiltration rate was only 3.2 mm/h, which confirms the tendency of these crusted soils to generate huge runoff at even small application rates. Received: 27 September 1997     

A spreadsheet model to evaluate sloping furrow irrigation accounting for infiltration variability

A spreadsheet model was developed to evaluate the performance of furrow irrigation that accounts for soil variability and requires few field measurements. The model adjusts an advance trajectory to three (advance distance, advance time) points and, similarly, it adjusts a recession trajectory to three (recession distance, recession time) points. The head of the furrow (distance = 0) is one of the points used to adjust both trajectories. It then calculates the parameters of the infiltration equation using the two-point method (based on the volume balance equation with assumed surface shape parameters). The model gives the option to enter an estimate of the soil infiltration variability in order to account for this variation when calculating irrigation performance indicators. The combination of variance technique was used for this purpose. A set of irrigation performance indicators (distribution uniformity, application efficiency, tail water ratio, deep percolation ratio and deficit coefficient) is calculated, assuming that the infiltrated water follows a normal frequency distribution. To illustrate the evaluation method, it was applied to three irrigation events conducted on a sunflower field, with 234 m long furrows spaced 0.75 m apart. The evaluations were performed in two 3-furrow sets. The application efficiency was satisfactory in the first irrigation, but low in the other two. Uniformity was high in all three irrigations. The performance indicator that was most affected by soil variability was distribution uniformity. Considering soil spatial variability was important for more realistic determination of the infiltrated water distribution, and therefore of the deep percolation, but it had less importance for the determination of the application efficiency, due to the relevance of runoff in our field application.     

Design procedure for border irrigation

An open-end graded border design procedure is presented. The proposed method based on the principle of mass conservation requires Kostiakov and Manning formulations for infiltration and roughness, respectively. The key assumption of the present design procedure is that the minimum infiltrated depth occurs at the lower border end and is equal to the required depth of infiltration. The philosophy behind the proposed design procedure is to select the appropriate flow rate q ₀ and cutoff time T _cof for given field conditions including the field geometry (field length and slope) and the soil characteristics (including the surface roughness coefficient and infiltration parameters). The results of two example border fields were in close agreement with those obtained from a zero-inertia model. Received: 23 December 1996     

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.     

Characterizing microtopographical effects on level-basin irrigation performance

Microtopography has long been recognized as one of the key variables in level-basin irrigation performance, although little effort has been devoted to establish its relevance. In this work, experimental data are used to quantify the influence of microtopography on irrigation performance. An irrigation evaluation was performed on a small level-basin (256 m²) LASER levelled to zero slope. Irrigation depth was gravimetrically measured and estimated at the 49 nodes of a regular network. Data from the irrigation evaluation and a two-dimensional flat-bed model were used to estimate irrigation depth. Irrigation times, soil surface elevation and distance to the inlet were estimated at the same nodes, and a correlation matrix was computed. Results showed that soil surface elevation was highly and significantly correlated with the times of advance (0.725⁷¹), recession ( −0.815⁷¹) and opportunity ( −0.852⁷¹), and with the measured irrigation depth ( −0.583⁷¹). Distribution uniformity using soil water measurements was 71.0%. Estimates from the irrigation evaluation and the two-dimensional model were 85.3% and 94.9%, respectively. The irrigation evaluation procedure could explain 30⁷¹% of the measured variability in irrigation depth. A large part of the unexplained variance in measured irrigation depth seems to be due to the spatial variation of infiltration properties. Predictions by the two-dimensional model were not significantly related to the measured values. A simple method was devised to estimate microtopography-adjusted irrigation performance from the results of a flat bed model and the standard deviation of elevation. Microtopography can have an important effect on level-basin irrigation performance. Models not considering this variable may incur large errors when simulating irrigation performance.     

土壤渗透特性的圆盘张力入渗法测定研究

以川中丘陵区紫色土为研究对象,采用圆盘张力入渗法,测定坡耕地和林地土壤在5个水头下(0、-1、-3、-6、-9cm)的导水率曲线,并对比分析野外圆盘张力入渗法和环刀土样室内降水头法测得的土壤饱和导水率的差异。结果表明,土壤稳定入渗率和非饱和导水率随负压绝对值的增大而降低,且坡耕地的变化幅度大于林地。野外圆盘张力入渗法测得的饱和导水率明显高于环刀土样降水头法的测定值。基于研究结果,推荐使用圆盘张力入渗法测定导水率曲线和饱和导水率。     

Spatial analysis of soil surface hydraulic properties: Is infiltration method dependent?

The management of irrigated agricultural fields requires reliable information about soil hydraulic properties and their spatio-temporal variability. The spatial variability of saturated hydraulic conductivity, K_s and the alpha-parameter α_vG-2007 of the van Genuchten equation was reviewed on an agricultural loamy soil after a 17-year period of repeated conventional agricultural practices for tillage and planting. The Beerkan infiltration method and its algorithm BEST were used to characterize the soil through the van Genuchten and Brooks and Corey equations. Forty field measurements were made at each node of a 6 m × 7.5 m grid. The soil hydraulic properties and their spatial structure were compared to those recorded in 1990 on the same field soil, through the exponential form of the soil hydraulic conductivity given by the Gardner equation, using the Guelph Pressure Infiltrometer technique. No significant differences in the results obtained in 1990 and 2007 were observed for either particle-size distribution or dry bulk density. The mean value of α_vG-2007 was found to be identical to that of α_G-1990, while that of K_s-2007 was significantly smaller than that of K_s-1990. In contrast to the Gardner equation, the van Genuchten/Brooks and Corey expression was found to be more representative of a well-graded particle-size distribution of a loamy soil. The geostatistical analysis showed the two parameters, K_s and α_vG-2007, were autocorrelated up to about 30 and 21 m, respectively, as well as spatially positively correlated within a range of 30 m. Despite the difference in the mean values of K_s between the two studies, the spatial structures were similar to those found in the 1990 experiment except for the covariance sign. The similarity in autocorrelation ranges indicate that the spatial analysis of soil hydraulic properties is independent of the infiltration methods (i.e., measurement of an infiltration flux) used in the two studies, while the difference in the covariance sign may be linked to the use of two different techniques of soil hydraulic parameterization. The covariance values found in the 2007 campaign indicates a positive relationship between the two parameters, K_s and α_vG-2007. The spatial correlations of soil hydraulic parameters appear to be temporally stabilized, at least within the agro-pedo-climatic context of the study. This may be attributed to the soil textural properties which remain constant in time and to the structural properties which are constantly renewed by the cyclic agricultural practices. However, further experiments are needed to strengthen this result.     

Varying irrigation rates effect on yield and yield components of chickpea

This study was conducted to determine the effect of different supplemental irrigation rates on chickpea grown under semiarid climatic conditions. Chickpea plots were irrigated with drip irrigation system and irrigation rates included the applications of 0 (I ₀) 25 (I ₂₅), 50 (I ₅₀), 75 (I ₇₅), 100 (I ₁₀₀), and 125 % (I ₁₂₅) of gravimetrically measured soil water deficit. Plant height, 1,000 seed weight, yield, biomass, and harvest index (HI) parameters were determined in addition to yield-water functions, evapotranspiration (ET), water use efficiency (WUE), and irrigation water use efficiency (IWUE). Significant differences were noted for plant height (ranging from 24.0 to 37.5 cm), 1,000 seed weight (ranging from 192.0 to 428.7 g), and aboveground biomass (ranging from 2,722 to 6,083 kg ha^?1) for water applications of I ₀ and I ₁₂₅. Statistical analysis indicated a strong relationship between the amount of irrigation and yield, which ranged from 256.5 to 1,957.3 kg ha^?1. Harvest index values ranged between 0.092 and 0.325, while WUE and IWUE values ranged between 1.15–4.55 and 1.34–8.36 (kg ha^?1 mm^?1), respectively.     

膜孔畦灌水流推进过程试验及数值模拟研究

利用膜孔畦灌田间水流推进实测资料,根据膜孔灌室内点源入渗模型验证了大田膜孔畦灌水流推进距离与时间呈乘幂函数的关系,并推求了不同开孔率情况下的膜孔灌点源入渗参数。假定不同的田间糙率基于SRFR软件对膜孔畦灌水流推进进行数值模拟,使模拟水流推进时间与真实情况达到最佳匹配,来确定田间的糙率,为膜孔畦灌技术要素设计及田间试验提供了参考。     

Tillage and irrigation effects on crop yields and soil properties under the rice-wheat system in the Indian Himalayas

Conservation tillage systems generally improve soil organic C (SOC), plant available water capacity (PAWC), aggregation and soil water transmission. A field experiment was conducted for 4 years (2001-2002 to 2004-2005) to study tillage (conventional tillage (CT) and zero tillage (ZT)) systems. The selected irrigation treatments were at four levels (I₁: pre-sowing (PS), I₂: PS + active tillering (AT)/crown root initiation (CRI), I₃: PS + AT/CRI + panicle initiation (PI)/flowering (FL), and I₄: PS + AT/CRI + PI/FL + grain filling (GF)), applied at the critical growth stages on rice (Oryza sativa L.) and wheat (Triticum aestivum L.). Their effects on direct seeded rice productivity and soil properties (SOC and selected physical properties) after rice and wheat harvest were investigated. Soil organic C contents after rice and wheat harvest in the 0-15 cm soil depth were higher under ZT than under CT. Soil organic C increased significantly with I₂ over I₁ for both crops and with I₄ over I₂ for the wheat crop. The PAWC was significantly higher with ZT than CT. Zero tilled and frequently irrigated plots showed enhanced infiltration characteristics (infiltration rate, cumulative infiltration and sorptivity) and saturated hydraulic conductivity. Both direct seeded rice and wheat yields were not significantly different in the plots under ZT and CT. There was a significant increase in both rice and wheat yields in the plots under I₂ over I₁. However, water use efficiency between irrigation treatments was not significantly different. Hence, under direct seeded rice-wheat system in a sandy clay loam soil of the sub-temperate Indian Himalayas, farmers may adopt ZT with two irrigations in each crop for optimum resource conservation.     

地面灌溉水流特性及水分利用率的数学模拟

在内蒙古风沙区一种砂土和壤质砂土的春小麦生育期内进行了畦田规格和灌水技术要素对水流推进和消退过程、田间水利用系数、灌水效率及灌水均匀系数影响的田间试验。并用SRFR406软件对畦灌条件下的水流特性及水分利用率进行了数学模拟。结果表明,运用SRFR模型能较好地模拟地面灌溉的水流推进及消退过程,尤其是推进过程模拟求得的结果与实测结果基本吻合。畦田的微地形对灌水效率的影响较大,尤其是畦田尾部反坡对灌水效率及水流推进与消退都有较大影响。为提高灌水效率,应加强耕作管理,消除反坡。畦田规格对灌水效率也有一定的影响,从获得较高灌水效率的角度来说,以畦宽2～3m、畦长50～60m较为适宜。     

Design of a farm layout for irrigation with limited discharges

In order to improve the irrigation efficiencies of small farms employing cavity wells for their water supply, an experimental study was conducted at the Central Soil Salinity Research Institute, Karnal. The cavity wells of the Karnal region do not have any discharge regulating devices for improving the irrigation efficiencies. The only way of improving these efficiencies is by designing an efficient irrigation layout, so that uniform water application is accomplished. The present study involves field determination of the opportunity time at each point along the border from advance and recession curves and computing the depth of cumulative infiltration from the infiltration rate curve. The irrigation efficiencies are also calculated from soil moisture measurements made before and after each irrigation.The results of this study show that a realistic field assessment of the irrigated border efficiencies is obtained through a soil moisture measurement procedure. The procedure, based on opportunity time and infiltration, overestimates the irrigation efficiencies due to the empirical nature of the infiltration equation. For small farms, with a limited discharge of 10 l/s, an irrigation layout of borders of 50–70 m in length and 6–8 m in width is recommended.     

Salinity and sodicity influences on infiltration during surge flow irrigation

The interactive influences of water quality and surge-flow irrigation (intermittent application of water) on infiltration into a bare loam soil, packed into a long metal flume, were measured with a laboratory recirculating infiltrometer devised for the experiments. Cumulative infiltration and final infiltration rates were measured over three irrigation episodes using synthetic waters of different qualities. Four water-quality combinations of low and high salinity levels (i.e., electrical conductivity, EC=1.5 and 7.5 dS/m) and low and high degree of sodicity [i.e., sodium adsorption ratio in the range of 5-10 and 25-35 mmol^1/2 l^-1/2] were tested. Results showed that surge-flow cumulative infiltration of low saline waters - especially during the first irrigation episode - was lower than the corresponding continuous-flow cumulative infiltration. Conversely, it was higher for high saline and high saline-sodic waters. Effects of the water-quality treatments on final infiltration rate were similar to and in agreement with the effects on cumulative infiltration. However, the range of the final infiltration rates among surge-flow treatments was larger than with the continuous-flow treatments. Overall, infiltration was higher with surge-flow application of high saline and high saline-sodic waters than with the continuous-flow treatment. The observed contrasting results for the surge effect with the low saline, high saline, and high saline-sodic water-quality treatments were attributed to soil consolidation, formation of a depositional seal layer, and the different levels of irrigation water salinity and sodicity. It was concluded that the "surge effect" phenomena (reduction in soil infiltration caused by surge flow) under brackish (saline, sodic, and saline-sodic) water application was not pronounced and had adverse effects, in comparison to the low saline-sodic water application. Consequently, from theory, practical application of surge-flow irrigation under these circumstances, from viewpoints of infiltration reduction and irrigation efficiency improvements, is questionable.