Research Paper
Abstract
Nitrogen is the primary nutrient that shows deficiency in saline areas, therefore, proper nitrogen fertilizer management is one of the strategies to achieve higher wheat grain yield. A field experiments in a saline soil was performed on wheat with a factorial arrangement in randomized complete ...
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Nitrogen is the primary nutrient that shows deficiency in saline areas, therefore, proper nitrogen fertilizer management is one of the strategies to achieve higher wheat grain yield. A field experiments in a saline soil was performed on wheat with a factorial arrangement in randomized complete block design with four replications, in Rostagh area, 25 km from Yazd. The first factor was nitrogen sources including urea, ammonium nitrate, and ammonium sulfate fertilizer, and the second factor was fertilizer use management consisting of four levels: 1- control (no nitrogen application), 2- recommended amount of fertilizer in three equal installments at the time of sowing, tillering, and heading stage, 3- recommended amount of fertilizer in three installments and 30% nitrogen in addition to the recommended rate in the tillering stage, and 4- recommended amount of fertilizer in three installments and 30% nitrogen in addition to the recommended rate at the heading stage. The results showed that the additional use of fertilizer at various growth stages had no significant effect on yield and its components. In comparison of urea to the other two fertilizers, ammonium nitrate had no significant effect in total yield of wheat in different fertilizer treatments, but using 30% nitrogen in addition to the recommended rate at tillering stage could cause significant differences in total yield when ammonium sulfate was used. Based on the results of this experiment, using nitrogen in peak times of consumption i.e. at tillering and heading, can reduce the loss of nitrogen from the soil, in addition to increasing grain and straw yield under saline conditions.
Research Paper
Abstract
Water balance components are difficult to measure in short intervals because their measurement is time consuming and costly. Therefore, soil-water--plant models can be used for prediction of these components. In this study, to predict grain yield and evaluate water use efficiency, an agro-hydrological ...
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Water balance components are difficult to measure in short intervals because their measurement is time consuming and costly. Therefore, soil-water--plant models can be used for prediction of these components. In this study, to predict grain yield and evaluate water use efficiency, an agro-hydrological model, namely, SWAP was used. This study covered a 10-years period from 2000-2010. Based on the data measured in the field, the model was first calibrated for part of the Doroudzan irrigation and drainage network (under Ordibehesht canal downstream lands) for 2000-04, then, it was verified for the years 2005-09. The simulation results of the components of water balance estimated by SWAP and statistical comparison between the simulation results showed that the SWAP model was able to estimate yield accurately. The R2 for the predicted and actual crop production was obtained at 0.98 and, based on average t-test and at 95% level, they were not significantly different. Using the simulation results after validation, water productivity for irrigation water (WPI), transpiration (WPT), evapotranspiration (WPET), and for irrigation and rainfall (WPI+R)were 0.77-2.08, 1.15-2.10, 0.68-1.26, and 0.6-1.37 (kg m-3), respectively. Soil evaporation and using surface irrigation system caused reduction of WPET in comparison to WPI.
Research Paper
Abstract
An accurate design of drip irrigation requires water quality analysis that helps attain a better emission uniformity coefficient. This study examined aquifer qualitative parameters in the north of Khuzestan province to assess the applicability of groundwater in trickle irrigation systems. For this purpose, ...
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An accurate design of drip irrigation requires water quality analysis that helps attain a better emission uniformity coefficient. This study examined aquifer qualitative parameters in the north of Khuzestan province to assess the applicability of groundwater in trickle irrigation systems. For this purpose, interpolation technology was used to map chemical parameters collected from 104 deep wells. At first, predicted values of each element were compared with the observed data using RMSE index to select the optimum interpolator technique. Interpolation and spatial analysis was carried out using geographical information system software in different layers. Evaluation factors including sodium adsorption ratio, SAR, total dissolved solid, TDS, total hardness TH, and Langelier saturation index, LSI, whichare often directly estimated from water analysis data such as calcium, magnesium, bicarbonate, potassium, and sodium. The results showed that the LSI was positive in 90 percent of wells. Total hardness in many parts of the study area was higher than 300 mg/L (very hard water), which indicated strong possibility of carbonate sedimentation and emitter clogging. Also, total dissolved solids in the south of the region was higher than 2000 mg/L.
Research Paper
Abstract
It is very important to find new and replaceable water resources for agricultural usage because of the increasing need of urban population and industries for high-quality water and decrease of drinking water supplies. To investigate the effect of different levels of irrigation water salinity, potassium ...
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It is very important to find new and replaceable water resources for agricultural usage because of the increasing need of urban population and industries for high-quality water and decrease of drinking water supplies. To investigate the effect of different levels of irrigation water salinity, potassium sulfate, and their interactions with yield and yield components of two barley cultivar, an experiment was conducted using a factorial arrangement in a completely randomized block design with four replications in 2012 at the greenhouse of Sari University of Agricultural Sciences and Natural Resources. The varieties of barley included Productive and Sahra, which were treated with different levels of water salinity (sea water) including well water (as control), mixture of 1/4, 2/4 , 3/4 sea water with well water, and sea water (pure). Potassium treatments included 0, 0.5, 1, and 1.5 g potassium per kg soil. In this experiment, seed yield, 1000 grain weight, number of heads, plant height, number of grains, number of spikes, biological yield, stem and leaf dry weight, and harvest index were measured. The results showed thatirrigation water salinity had negatively affected all these plant traits, except for harvest index. The highest decrease of salinity with 51.8% was observed in the number of spikes. Application of potassium also led to the improvement of yield and yield components and decreased harvest index, but was non-significant for all the traits except straw yield. The stem and leaf dry weight and biological yield showed the highest effect in response to addition of 1.5 g potassium per kg soil, with increases of 35.70% and 25.2%, respectively.
Research Paper
Abstract
Water resources are limited in most parts of the country, including Isfahan,where cotton is cultivated but it’s planting time coincides with the sensitive stage of cereal grain growth. Therefore, developing and adopting techniques that could maximize use of the existing resources is needed. ...
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Water resources are limited in most parts of the country, including Isfahan,where cotton is cultivated but it’s planting time coincides with the sensitive stage of cereal grain growth. Therefore, developing and adopting techniques that could maximize use of the existing resources is needed. To study the effect of basin and furrow irrigation methods on yield and some yield components of cotton as well as the impact of the transplanting, this experiment was carried out in a randomized complete block design with three replications in Rodasht agricultural research station for two years (2003 and 2004). The variables studied included basin and farrow irrigation methods and four planting dates (transplanting). The irrigation method affected the10-boll weight, water use efficiency, and water consumption. Also, the results showed that planting date affected water consumption, yield, water use efficiency, boll number per plant, and 10-boll weight. In general, the furrow irrigation method, compared with basin irrigation method, used about 11 percent less water. Finally, if for any reason cotton could not be planted on proper time, the crop can be seeded in the nursery and its seedling transplanted in the main field after 20 days.
Research Paper
Abstract
This paper describes the extension requirements in use of drip irrigation systems in Tehran province. The study was functional (practical) in terms of goal, non-experimental in terms of control on variables, and causality-relational in terms of data collection. Data collection method was based on the ...
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This paper describes the extension requirements in use of drip irrigation systems in Tehran province. The study was functional (practical) in terms of goal, non-experimental in terms of control on variables, and causality-relational in terms of data collection. Data collection method was based on the documentary-library and field study (questionnaire) and statistical population included 547 samples of orchardists in Tehran province who used drip irrigation system in their farms. Sample size was calculated by Cochran formula equal to 192 persons and sampling method was simple relative random. To determine the questionnaire validity, comments and suggestions of faculties, agricultural extension researchers, and experts were used. The reliability of the questionnaire was determined by the Cronbach alpha coefficient at 87%. The results of multiple regression showed that the variables included requirements of educational-extension programs, cultural-social requirements, economical-agricultural requirements, human resources requirements, and educational-extension services had a positive role on the usage of drip irrigation systems. Furthermore, the mentioned variables explained 60 percent of changes in the dependent variable.
Research Paper
Abstract
This study was performed to investigate the effect of different levels of irrigation water applied in tape drip irrigation on yield, seed yield components, oil yield, seed oil percent, and seed water use efficiency (WUE) of two canola varieties in Behbahan Agriculture Research Station in 2009 and 2010 ...
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This study was performed to investigate the effect of different levels of irrigation water applied in tape drip irrigation on yield, seed yield components, oil yield, seed oil percent, and seed water use efficiency (WUE) of two canola varieties in Behbahan Agriculture Research Station in 2009 and 2010 seasons. The experiment was performed in split plots as a randomized complete block design with 4 replications. The main factor was the different levels of irrigation water (50%, 75%, 100%, and 125% of water requirement) in tape drip irrigation and the sub factors were two canola varieties including hybrid Hyola 401 and RGS003. The results showed that the effect of different irrigation water amounts on seed yield and its components and the seed WUE was statistically significant at 1% level. The effect of canola variety on seed yield, seed thousand weight, the number of seed in capsule and seed WUE was significant at 1% level and the best variety was hybrid Hyola 401. The highest seed yield was found for the treatments 125% water requirement (3161 kg/ha) and 100% water requirement (3053 Kg/ha), respectively. However, the treatment of 100% water requirement was the best treatment as it consumed less water. The WUE in the best treatment i.e. canola hybrid Hyola 401 with 100% water requirement, was 0.81 kg/m3.
Research Paper
Abstract
Pistachios are salt tolerant crops, but the degree of salt tolerance of pistachio cultivars grown in northern parts of Yazd province, Iran, is not adequately known. In order to evaluate the effect of saline water on the growth and chemical composition of pistachio seedlings, a glasshouse experiment was ...
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Pistachios are salt tolerant crops, but the degree of salt tolerance of pistachio cultivars grown in northern parts of Yazd province, Iran, is not adequately known. In order to evaluate the effect of saline water on the growth and chemical composition of pistachio seedlings, a glasshouse experiment was conducted on five cultivars of pistachio namely, Hajabdolahi, Hajagha-Ali, Jalilaghaii, Parandi, and Lorgi. The experimental design was complete randomized block with three replications in the form of factorial experiment. Treatments included five pistachio cultivars and four levels of salinity (0.5, 5, 10, 15 dS/m). Seedlings were harvested after six months and growth and chemical parameters were measured for roots and shoots (stem and leaves). Increase in irrigation water salinity resulted in increasing Na concentration, shoot length, and K/Na ratio. Results also showed that in comparison to the other cultivars, Parandi could produce more biomass yield under higher level of salinity. Due to high K/Na ratio, Parandi cultivar could be considered as a salt tolerant rootstock under saline conditions.
Research Paper
Abstract
Continuous availability of soil water is an important factor for plant growth. Both lack of adequate access to water in soils, or adequate oxygen in saturated soils, may reduce or even stop plant growth. To study the behavior of pistachio seedling at various moisture levels and to determine non-limiting ...
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Continuous availability of soil water is an important factor for plant growth. Both lack of adequate access to water in soils, or adequate oxygen in saturated soils, may reduce or even stop plant growth. To study the behavior of pistachio seedling at various moisture levels and to determine non-limiting water range for its growth, a greenhouse experiment with a completely randomized design was conducted at two levels of bulk density (BD) i.e. 1.5 and 1.8 g cm-3, six moisture levels for BD 1.5 g cm-3 (33-43%, 25-33%, 19-25%, 14-19%, 11-14%, and 7-11% on volume basis) and BD level of 1.8 g cm-3 (27-33%, 23-27%, 19-23%, 15-19%, 13-15%, and 8-13% v/v), with three replications. After transferring the pistachio cv. Sarakhsi seedlings (Pistachio vera L.) into soil cylinders and their establishment, six different volumetric water contents for each BD level were applied. Stomatal conductance of the third mature leaf, proline content, leaf relative water content (RWC) and leaf area were determined. The effect of moisture levels on all growth parameters were significant (P<0.01). With bulk density of 1.5 g cm-3, the seedlings experienced vegetative and physiological limitations in the range of 7 to 14 percent volumetric water content, thus, non-limiting water range for pistachio seedling at this BD level ranged from 14 to 43 percent v/v. In the compacted treatment (BD of 1.8 g cm-3), the vegetative growth and physiological activities suffered limitations within the range of 8-19 percent water content due to moisture deficit, and, in the range of 23-32, were retarded due to soil poor aeration. Also, non-limiting water range at this BD ranged from 19-23 percent water content. The least limiting water range predicted from Dasilva et al. model at the two BDof 1.5 and 1.8 g cm-3 were 11- 25% and 20- 22 percent, respectively. The differences between the predicted range and the range obtained based on the seedling response implies the need for the calibration of the predicting model for each particular soil and plant.
Research Paper
Abstract
Potato is one of the sensitive plants to drought stress and it is one of the main crops in the north regions of Fars province. Since the planting time is simultaneous with wheat irrigation period, due consideration should be given to reduce irrigation consumption for this crop. This research investigated ...
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Potato is one of the sensitive plants to drought stress and it is one of the main crops in the north regions of Fars province. Since the planting time is simultaneous with wheat irrigation period, due consideration should be given to reduce irrigation consumption for this crop. This research investigated the effect of potassium sulfate on the drought tolerance of potatoes. Field experiment was arranged in split plot design with three replications. Irrigation intervals and potassium sulfates were allocated to main and subplots, respectively. Different treatments included various levels of potassium sulfate i.e. according to the soil test results, 20% and 40% below soil test results, and 20% and 40% more than soil test results, and irrigation intervals of 6 days, 12d, and 18 d. Plant measured responses included the tuber yield per hectare, means of weight and size of a tuber, tuber weight per plant, and also number of tubers per plant. Results showed that the highest yield was found in the 6-day interval irrigation and potassium sulfate at the rate of 40%> soil test results. However, in water deficit conditions, the 12-day interval and potassium sulfate use up to 40% > soil test results can be recommended as appropriate for avoiding potato yield decrease in the study area.
Research Paper
Abstract
In this research, effects of subsurface drip irrigation method on soil and tomato yield was investigated under different salinities and two irrigation management strategies: M1= alternating irrigation with fresh water and saline water, and M2= saline water in the first half of each irrigation event and ...
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In this research, effects of subsurface drip irrigation method on soil and tomato yield was investigated under different salinities and two irrigation management strategies: M1= alternating irrigation with fresh water and saline water, and M2= saline water in the first half of each irrigation event and fresh water in the second half. The experiment was conducted in 320 m2 area including 30 plots. Drippers were placed at 15 cm depth and, in order to consider the interaction of salinity levels and management strategies, split plot design with three replications was used in which management strategies (m1 and m2) were in the main plots and subplots contained different levels of salinity including 0.68, 2, 4, 6, and 8 dS/m (S0, S1, S2, S3, and S4, respectively). Results showed that yield of tomato decreased with increasing irrigation water salinity levels and the highest and lowest yields were in the M2S0 (52.44 ton/ha) and M1S4 (23.363 ton/ha) treatments, respectively. Also, average yield in M1 strategy was 17.77 % less than M2 strategy. Applied irrigation water decreased with increasing salinity levels and, therefore, water use efficiency (WUE) increased. The highest WUE was in the M1S4 (7.78 kg/m3) and M2S4 (7.77 kg/m3). The ECe measurement in various depths down to 90 cm revealed that the highest ECe (3.36 dS/m) occurred in different depths in M2S4 treatment.
Research Paper
Abstract
Water crisis is one of the basic problems in the arid and drought prone areas like Iran. This condition in the recent years has aggravated due to drought phenomenon. Thus, using poor water quality has increased in areas where good quality is not available. In this study, in order to investigate clogging, ...
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Water crisis is one of the basic problems in the arid and drought prone areas like Iran. This condition in the recent years has aggravated due to drought phenomenon. Thus, using poor water quality has increased in areas where good quality is not available. In this study, in order to investigate clogging, 5 types of emitters including Micro flapper, Netafim, Corona, Axios and Iran Drip were tested at two different flow rates (8/6/4/2 L/h). The experiment was carried out in Samandak village in Sari district and had four irrigation management treatments including untreated well water (S1), acidification (S2), acidification-fertigation (S3), and fertigation (S4). The results showed that the Netafim emitter (8 L/h) had minimum clogging while the micro flapper (2 L/h) had the maximum clogging among all of the tested emitters. Also, acidification treatment (S2) had minimum clogging. The results indicated that in a given type of emitter, the flow rate reduction due to clogging decreased with increasing emitter flow. Statistical analyses of the data showed that the effects of irrigation management factor and emitter factor were significant in variation of flow rate, but there was no significant interaction between these factors. Study of the discharge coefficient of variation and coefficient of uniformity revealed that acidification was a management strategy in the control of emitter clogging and maintenance of high uniformity in the trickle irrigation systems.
Research Paper
Abstract
Infiltration and its modeling are important in design and implementation of irrigation projects, drainage, water-resources management, soil-conservation, hydrological studies, and artificial-recharge of groundwater and are influenced by different characteristics of soil and infiltrated water including ...
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Infiltration and its modeling are important in design and implementation of irrigation projects, drainage, water-resources management, soil-conservation, hydrological studies, and artificial-recharge of groundwater and are influenced by different characteristics of soil and infiltrated water including the amount of salinity and sodium. The aim of this study was to evaluate the infiltration models of Kostiakov-Lewis, Kostiakov, Horton, SCS, and Philip using water salinity levels of 0.5, 3, 6, and 12 dS m-1 and SAR of 0.5, 10, 20, and 30. Infiltration was measured using double rings method with 5 replications on two calcareous soil-series of Daneshkadeh and Kooye-Asatid from Agricultural Research Station of Agricultural-College, Shiraz-University located in Bajgah region and the models were fitted to them. Calculating coefficient of determination (R2), efficiency percentage (EP) of model, and normalized root mean square error (NRMSE), the performance of each applied model was evaluated and ranking of models were performed. The model that ranked the highest was considered as the best and the most stable model. The Kostiakov-Lewis model with R2, NRMSE and EP of 0.997, 0.205 and 99.81 and SCS model with the aforementioned statistics of 0.992, 0.249and 98.76, respectively, were the most and the least suitable models in both of the studied soils and in almost all of the applied water quality treatments. Therefore, the Kostiakov-Lewis model can be used for modeling water infiltration into soil with an acceptable confidence in arid and semiarid regions, where waters with poor quality are often used.
Research Paper
Abstract
Plant performance and freshness is related to the pattern of its root growth development, which is highly affected by the water amount and water use management. Therefore, the spatiotemporal variation of maize root under five treatments including full irrigation treatment (FI), partial root-zone drying ...
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Plant performance and freshness is related to the pattern of its root growth development, which is highly affected by the water amount and water use management. Therefore, the spatiotemporal variation of maize root under five treatments including full irrigation treatment (FI), partial root-zone drying treatments at two levels (receiving 75% of ET =PRD75, and 55% of ET= PRD55) and deficit irrigation treatments at same levels (75% =DI75 and 55% =DI55) was investigated using a completely randomized block design in 2011. Root growth parameters including root volume, root area, root length, and root wet and dry mas were measured at each 10 cm soil depth interval down to 100 cm soil depth. Sampling locations were at 0.0 cm from the first lateral (R1), 18.75 cm (R2), 37.5 cm (R3), 55 cm (R4), and 75 cm (R5). Results demonstrated that FI treatment received 531 mm irrigation water while applying PRD75 and RDI75 caused 17.3% water saving during the whole growing season and applying PRD55 and RDI55 caused 31.3% saving. Analyzing the values of measured root growth parameters showed that the highest and the least values in all samples were in PRD75 and RDI55 treatments, respectively. Also, most part of the root was distributed in 0-20 cm soil depth and up to 20 cm apart in both sides of the plant. The least values of root growth parameters were at 50-60 cm soil depth in RDI treatments and at 60-70 cm soil depths in PRD treatments. Also, results demonstrated that there was no significant difference between the measured values of root parameters in PRD75 and RDI75 with those in FI treatment. Therefore, applying PRD75 and RDI75 caused both water saving and an optimum root development, which led to a better utilization of soil water content under water stress. Thus, both RDI75 and PRD75 treatments are appropriate strategies to deal with the water shortage and to reach a sustainable agriculture.
Research Paper
Abstract
Designing and scheduling of drip irrigation systems are often done without enough information about water distribution in the soil. Due to tillage operations and crop production practices, agricultural soils can be considered as two layered soils with different bulk densities. The top soil layer has ...
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Designing and scheduling of drip irrigation systems are often done without enough information about water distribution in the soil. Due to tillage operations and crop production practices, agricultural soils can be considered as two layered soils with different bulk densities. The top soil layer has a lighter texture than the sub soil layer. In this research, the development of the wetting front and moisture distribution in a two-layered soil were investigated. The filed experiments were performed in the Tabriz University’s Research Farms, in order to determine the characteristics of the wetting patterns of drip irrigation under linear sources in a two layered soil. To study the effects of application duration and volume of water applied on the horizontal and vertical dimensions of wetting pattern, the experiments were conducted with four durations of 1, 3, 5, and 7 hours. The results showed that increasing the application duration increased the horizontal and vertical dimensions of the wetting patterns. But, after 5 hours, the application duration had no significant effect on the wetting pattern dimensions. In the subsoil layer, due to its heavy texture, vertical movement of the pattern was very slow and increase in the application duration more than 5 hours only caused increase in the volumetric moisture of the wetted soil. Using HYDRUS-2D model, the field experiments were simulated under the same conditions, too. The comparisons between model simulations and experimental results showed satisfactory agreement. According to the results, it can be demonstrated that the accuracy of HYDRUS- 2D in a two layered soil decreased when the wetting pattern reached the 2nd layer.
Research Paper
Abstract
An experiment was conducted in 2011 to evaluate the effect of weed interference on sunflower yield in deficit irrigation and to study the grass and broadleaf weeds growth at different moisture condition. The experiment was arranged as factorial, randomized complete blocks with four replicates per treatment. ...
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An experiment was conducted in 2011 to evaluate the effect of weed interference on sunflower yield in deficit irrigation and to study the grass and broadleaf weeds growth at different moisture condition. The experiment was arranged as factorial, randomized complete blocks with four replicates per treatment. Treatments included different moisture conditions [40%, 60%, 80%, and 100 percent of crop water requirement (CWR)], and two weed interference levels: hand weeding and weedy condition. A plot with furrow irrigation was kept as control. The results showed that sunflower grain yield was significantly affected both by moisture condition and weed interference. Weed competition decreased crop grain yield by 23%, 21%, and 30% in tape irrigation at 100% and 80% CWR and furrow irrigation treatments, respectively. Weed biomass severely decreased as water deficiency increased. The maximum weed biomass was observed in the tape irrigation with supplying the 100% of CWR, which was 17% greater than the furrow irrigation. Weed biomass also decreased with increasing the water stress up to 64%. In regions where water resources are limited and farmers have to use deficit irrigation, the joint effect of weed competition and drought stress may be severely harmful to crop yield; therefore, controlling weeds at the earliest possible time is crucial to save the stored moisture for crops.
Research Paper
Abstract
Regarding increased limitations on fresh water availability in agriculture and the necessity of finding solutions for management of unconventional waters, some scenarios for using saline water were assessed for forage maize. SALTMED model, as an integrated approach, can be used for a variety of irrigation ...
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Regarding increased limitations on fresh water availability in agriculture and the necessity of finding solutions for management of unconventional waters, some scenarios for using saline water were assessed for forage maize. SALTMED model, as an integrated approach, can be used for a variety of irrigation systems, soil types, soil stratifications, crops, water management strategies (blending or cyclic), leaching requirements, and water quality. In this study, SALTMED model was evaluated in condition of the frequency of salt water with fresh water for forage maize. Three salinity levels i.e. 0.4 (as control treatment), 3.5, and 5.7 dS/m, were used in this research. Irrigation was carried out using tape (drip irrigation) with separate control in each plot. Crop yield (based on biomass) was considered as a parameter to evaluate the model for nine different treatments (regarding saline and fresh water application). The results showed that the performance of the model in prediction of the crop yield was satisfactory. The relative errors between the observed and the predicted data were between 0.0 and 24.7%. Moreover, there was a good correlation (coefficient of determination= 0.79) between the observed and predicted crop yield values. Statistical test also indicated that there was no significant difference between the observed and predicted values. Thus, SALTMED model could be a useful tool for on-farm water management and predicting crop yield.
Research Paper
Abstract
Determination of crops water requirement in different environmental conditions is essential for preparation of precise and suitable irrigation scheduling. The effect of soil compaction and texture on crop coefficient and evapotranspiration of maize was investigated in this study, which was conducted ...
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Determination of crops water requirement in different environmental conditions is essential for preparation of precise and suitable irrigation scheduling. The effect of soil compaction and texture on crop coefficient and evapotranspiration of maize was investigated in this study, which was conducted as a factorial experiment with a completely randomized design in a research farm in Jey and Qahab district in Isfahan. The study included three soil texture treatments of silty clay loam, loam, and sandy loam, and three compaction treatments including natural density of field soils, compaction by dropping 2.5 kg weights 25 and 50 times (based on the standard Proctor test). In order to determine the reference evapotranspiration of maize, evaporation pan method was used, and for actual evapotranspiration, volumetric soil water balance method was adopted by using micro-lysimeters-drains (32 cm diameter and 80 cm height). The results showed that by increasing soil compaction crop evapotranspiration and crop coefficient of maize were reduced at the different growth stages. The maximum 10-day average evapotranspiration of maize was obtained at 8.76 mm/day in silty clay loam soil with natural bulk density of 1.27 g/cm3. This value was 70 percent higher than the minimum 10-day average evapotranspiration in the fifth decade of growth. Increasing the soil bulk density decreased total crop evapotranspiration 23%, 20.8%, and 12.8% in loam, silty clay loam, and sandy loam soil, respectively. The maximum and minimum impact of soil bulk density on crop coefficient of maize was observed in the middle and initial growth stages, respectively. The maximum and minimum impact of increased soil bulk density on reduction of crop coefficient of maize in the middle growth stage was 40.3% in loam soil and 20.7% in sandy loam soil for the second bulk density treatment.
Research Paper
Abstract
An appropriate method to determine the hydraulic conductivity above water table is Guelph Permeameter. Using this method, experiments can be carried out by one person in a short period. Several investigators have commented on the systematic difference between the hydraulic conductivity obtained by Guelph ...
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An appropriate method to determine the hydraulic conductivity above water table is Guelph Permeameter. Using this method, experiments can be carried out by one person in a short period. Several investigators have commented on the systematic difference between the hydraulic conductivity obtained by Guelph Permeameter and Shallow Well Pumping Test (SWPT) methods. Therefore, the purpose of this research was to find a relationship between these two methods. In this study, to determine soil saturated hydraulic conductivity with Guelph Permeameter, Guelph Permeameter test was carried out in 5 agricultural regions of Khuzestan province and calibration of Guelph data was carried out with SWPT. In each region, Guelph Permeametertests were conducted in 40 holes with 60 cm depth, under two (5 and 10 cm) constant heads in each hole. Five holes with 1m depth were dug to carry out the SWPT in all regions mentioned above. In each region, the number of holes with negative results and the ones with significant results for Kfs and in Guelph Permeameter were identified. Using Laplace single head analysis with zero capillary, single head analysis of Richards with α* = 12 and single head regression based on Richards analysis were used to remove non-logical results of Guelph Permeameter device. It was observed that the geometric mean of regression based on Richards and double head analysis were equal. Coefficients related to this analysis were determined using least squares, and mean of α* = 12 became equal to the primary hypothesis at a significance level of 95 %. In addition, because the standard deviation of α* in Guelph tests was high, it was better to consider it constant. It is concluded that in regions with average soil texture, hydraulic conductivity value obtained in shallow well pumping method was 4-5 times more than the hydraulic conductivity measured by Guelph method, while in regions with heavy soil texture, value of the hydraulic conductivity measured by shallow well pumping method was 2-3.5 times more than the hydraulic conductivity determined by Guelph method.
Research Paper
Abstract
Parameter uncertainty analysis of hydrological models and identifying the statistical characteristics of model output based on the relation between model inputs and parameters is one of the most important issues in hydrological modeling. In this study, the Generalized Likelihood Uncertainty Estimation ...
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Parameter uncertainty analysis of hydrological models and identifying the statistical characteristics of model output based on the relation between model inputs and parameters is one of the most important issues in hydrological modeling. In this study, the Generalized Likelihood Uncertainty Estimation (GLUE) was used for calibration and uncertainty analysis of soil hydraulic parameters of SWAP (Soil, Water, Atmosphere and Plant) agro-hydrological model based on measured soil moisture in a maize field in Borkhar area, Isfahan province. Results showed that the θrand Ks out of the six Van Genuchten-Mualem parameters, were the most non-identifiable parameters in calibration process and had much contribution into the soil moisture uncertainty in SWAP. Moreover, results confirmed that in Van Genuchten-Mualem equation, the soil hydraulic parameters are fitting parameters and fixing some of them during the calibration process was not realistic. Finally, results indicated that the GLUE method could successfully calibrate the model for soil moisture simulation during the growing season, with most of the measured data (about 75%) falling in the 95% confidence interval.