مجله پژوهش آب در کشاورزی
سال سی و چهارم شماره 1 (بهار 1399)

In order to determine salinity tolerance threshold and yield decrease per unit increase of soil salinity in selected pomegranate genotypes, a factorial experiment was carried out based on completely randomized design (CRD), with two factors: genotypes in 12 types (Shisheh Kap Ferdus, Malas Yazdi, Malas Saveh, Rabab Neyriz, Golnar Saveh, Golnar Sarvestan, Golnar Shahdad, Narak Lasjerd Semnan, Vahshi Babolsar, Post Siyah Ardakan, Chah Afzal and Voshik Torsh Saravan) and soil salinity at five levels (1.5, 3.8, 6.2, 9.3 and 12.6 dSm-1). According to the results, the lowest salinity tolerance threshold was observed in Voshik Torsh Saravan (3.02 dS/m), Malas Saveh (3.25 dS/m) and Golnar Saveh (3.40 dS/m) genotypes, and the highest salinity tolerance threshold was observed in Golnar Shahdad (4.90 dS/m), Chah Afzal (4.70 dS/m), Post Siyah Ardakan (4.38 dS/m), and Malas Yazdi (4.17 dS/m) genotypes. The highest yield reduction slope was observed in Golnar Saveh (7.89%), Golnar Sarvestan (7.39%), Voshik Torsh Saravan (6.69%), and Malas Saveh (6.33%) genotypes, respectively. In contrast, the lowest yield reduction slope was observed in Chah Afzal (2.83%), Post Siyah Ardakan (2.88%) and Narak Lasjerd Semnan (2.89%) genotypes, respectively. Overall, the results showed the levels of salinity that reduced the yield by 50% in Chah Afzal, Post Siyah Ardakan and Narak Lasjerd Semnan genotypes were about twice greater than salinity that reduced the yield by 50% in Golnar Saveh, Golnar Sarvestan, Voshik Torsh Saravan and Malas Saveh genotypes. EC50 in Chah Afzal, Post Siyah Ardakan, and Narak Lasjerd Semnan genotypes were observed at 22.37, 21.74 and 21.10 dS/m. At salinity level of 8.4 dS/m, yield reductions in Chah Afzal, Post Siyah Ardakan and Narak Lasjerd Semnan genotypes were only 10.47%, 11.58%, and 13.30%, respectively, which were lower than the 50% value previously reported. Therefore, these three genotypes were selected for further studies and planting as rootstocks in Chah Afzal Station of National Salinity Research Center.

This study was conducted to simulate water balance components at field scale, predict soil moisture profile, and grain yield in irrigated wheat fields in Neyshabur plain. In this regard, three farms were selected in different parts of the plain. AquaCrop input data including air, soil, and crop parameters were collected at each farm separately, then, the required model parameters and wheat crop data were calibrated. Root mean square error (RMSE), model efficiency (EF) and prediction error (Pe) were used to evaluate the model performance. The results of moisture simulation in soil profile showed that the model correctly simulated moisture content at different depths and times. The statistical parameters used for evaluating efficiency of the model at the calibration stage for simulating soil moisture in all farms were 0.027<RMSE<0.032, 0.80<EF<0.91, and 3.5<Pe<14%. These values at model validation stage were 0.025<RMSE<0.031, 0.82<EF<0.94, and 2.7<Pe<12%. The minimum and maximum percentages of model simulation error for grain yield and water productivity in all farms managed by the farmers were 4-8.8% and 4.6 to 9%, respectively. According to the results of the research, AquaCrop model can simulate soil moisture content, grain yield, and water productivity with acceptable accuracy under similar field conditions.

Due to shortage of fresh water resources and increase in the salinity of soil and water resources, use of halophytes has a great importance for forage production and human food security. To compare the effect of different irrigation methods (furrow, bubbler, and drip) on some halophyte forage species, a research was conducted in Sadooq Salinity Research Farm of NSRC in Yazd, Iran, for three years. The experimental design was arranged in complete randomized block design in the form of split plot with three replications, Main plots were different irrigation methods (furrow, bubbler, drip) and halophyte species (A. canescens, A. halimus, A. lentiformis, A. nummularia, and K. indica) were laid out as sub main plots. All plots were irrigated with saline water of 14 dSm-1. During the growing season, all plants were cut every 3-4 months and yield and yield component as well as water use efficiency were measured. Results indicated that A. canescens, followed by A. halimus, with yield of 7.48 and 3.28 ton/ha dry forage, respectively, had the highest forage yield with significant differences (p< 0.05) with each other and with other treatments. Results showed that, under furrow irrigation method, A. canesence and K. indica had the maximum and minimum water use efficiency, respectively. The same trend was also observed for bubbler and drip irrigation methods, as A. canesence had the maximum of water use efficiency under these methods. Based on the results, the highest water use efficiency (2.26 kg/m3) was observed for A. canesence irrigated with bubbler method, and the lowest (0.07 kg/m3) was for K. indica under drip irrigation method. Consequently, based on the results of this experiment and considering the economical and operational aspects of irrigation methods, A. canesence, with dry yield of 7.73 and 8.81 ton/ha under furrow and bubbler irrigation methods, respectively, could be introduced as the best halophyte species for forage production under saline conditions. The results will be more helpful if the experiment is carried out again with determination of water requirement for each plant based on evapotranspiration or soil moisture fluctuations.

Realistic agro-hydrological modeling of the sugarcane fields with subsurface drainage in Khuzestan Province, Iran, is a challenging problem, due to rapid fluctuations of the shallow groundwater and, hence, water balance components, and significant size (~ 20 ha) of the fields. In this work, a distributed agro-hydrological modeling scheme was developed through the application of a modified version of the SWAP model and an improved variant of Unified Particle Swarm Optimization (UPSO) algorithm with capability of sub-daily calibration and simulation of controlled drainage. The developed modeling scheme was applied to a sugarcane (CP48-103 cultivar) field with controlled drainage (at 90 cm below ground level) in Imam Khomeini Sugarcane Agro-industrial Company farms, during 2010-2011 (481 days). The results demonstrated the success of the developed modeling scheme in retrieving the measured soil moisture, groundwater level, subsurface drainage outflow (with an EF of 0.829, 0.922, and 0.857 for calibration dataset; and 0.877, 0.781, and 0.712 for validation dataset, respectively), soil water solute concentration, subsurface drainage outflow salinity (with a NRMSE of 0.124 and 0.079 for calibration dataset; and 0.152 and 0.072 for validation dataset, respectively), Leaf Area Index, cane yield, and sucrose yield (with an EF of 0.997, 0.993, and 0.988, respectively). Based on the solute balance components simulated throughout the simulation period, ~ 30.10 ton salt ha-1 was added to the soil due to saline irrigation water, and ~ 45.25 ton salt ha-1 was discharged into the receiving water bodies via surface/subsurface field drains.

Salinity and drought stress are the most important factors that limit plant growth, especially in dry and semi-arid regions. To investigate the effects of irrigation water levels and salinity on yield and yield components of wheat cultivar Sirvan, a factorial experiment was conducted in a complete randomized block design with three replications in the research field of agricultural faculty of the University of Birjand during the growing season of 2017-18. The treatments included irrigation at four levels (125%, 100%, 75%, and 50% water requirement) and water salinity in three levels (1.6 dS.m-1, 6 dS.m-1, and 7.8 dS.m-1). The results showed that yield components, biological yield, and grain yield of wheat were affected by water irrigation levels and water salinity. Moreover, these treatment significantly reduced the yield components, harvest index, and water use efficiency (WUE). In biological and grain yield of wheat, the highest and the lowest amounts belonged to 125% water requirement × salinity of 1.6 dS m-1 by 1535and 588.76 g m-2, respectively. In biological yield and grain yield, there was no significant difference observed between 125% wheat water requirement × salinity’s of 1.6% dS.m-1 and 100% water requirement × salinity of 1.6% dS.m-1 treatments. Biological and grain yield of wheat decreased to 65% in 50% water requirement × salinity of 7.8 dS m-1 compared with 125% water requirement × salinity of 1.6% dS.m-1. According to results of this experiment, 125% and 100% water requirement treatments had the highest biological and grain yield. Although 125% wheat water requirement had the highest value in all traits but they were not significant compared to 100% water requirement treatment. In water salinity treatments, non-stress levels had the best performance. According to the results of this study, to avoid salt accumulation in the root zone under saline water irrigation and to decrease negative salinity effects, irrigation must be applied based on wheat water requirement.

Due to the quantitative and qualitative decline of groundwater resources, it is essential to optimize the water use in agriculture. One of the methods to optimize water use in agriculture, especially in arid and semi-arid regions, is to use yield-water-salinity functions. Therefore, this study was performed for prediction of spinach yield and yield components and determination of optimal production function under salinity and water stress conditions in Kashmar region, Iran. A factorial experiment was performed in a completely randomized block design with four replications including three salinity levels (i.e. S1= 0.75, S2=4, S3= 8 dS/m) and three levels of irrigation (including full irrigation (100% of water requirement)) = I1, I2=75% I1, and I3= 50% I1). Yield and yield components data of spinach (including leaf area, plant height, stem height, root length, plant dry weight, and root dry weight) were fitted to different production functions including simple linear, Cobb-Douglas, quadratic, and transient models. Optimal production function of spinach was determined after determining the coefficients of different functions. To evaluate different functions, the statistical indices of normalized mean square error, mean absolute error, modeling efficiency, agreement index and explanation coefficient were used. The results showed that the coefficient of determination (R2) for estimation of the biomass weight by quadratic, transcendental, simple linear, and Cobb-Douglas functions were 0.938, 0.890, 0.888 and 0.867, respectively. Most of the values of normalized mean square error and mean absolute error belonged to the simple linear functions and Cobb- Douglas. According to the results of this research, the quadratic production function is recommended as the optimal production function for yield and yield components of spinach.

Soil water is an important factor in the growth of the plant. There are different methods for soil moisture estimation. It is time-consuming to obtain volumetric soil moisture in a laboratory. This study was performed to evaluate estimate of soil moisture by different in situ methods including the electrical resistance of Werner electrode arrangement and ground penetration radar (GPR) from 700 MHz antenna, and two humidity sensors, namely, thetaml2 and sm300. These were used in 72 soil samples with different textures (loam, sandy clay loam and silty loam, silty clay, silty clay loam, clay loam) in parts of Shahrekord Watershed.The results showed that the coefficient of correlation between soil moisture and electrical resistance was 0.85. Also, the correlation coefficient between the values obtained from subsurface radar method, sm300 sensor and thetaml2 with the results obtained from laboratory measurements were 0.86, 0.94, 0.86, with CRM index values of -0.52, -0.75 and –1.22. By comparing the results of electrical resistivity, moisture from the GPR and the sm300 and thetaml2 sensors with volumetric moisture, the Root Mean Squared Error (RMSE) values were 8.41, 4, 5.3 and 8.6; and RRMSE were 10, 31, 29, and 26, respectively. Duncan test of moisture content showed that the difference between the sensors and the laboratory moisture content was significant at 5% level (p<0.05). According to the value of RRMSE All sensors had a good estimate of soil moisture. In conclusion, electrical resistivity and GPR method, due to higher sampling density, could be used as a rapid, cost effective, and non-destructive technique to estimate profile of soil water content at scales of field to sub-watershed.

Estimation of wetting front dimensions enhances the water use efficiency and optimal use of water. Since, globally, most of the cultivated lands are not flat, full recognition of the moisture advance front is essential for proper management and operation of surface drip irrigation in these areas. In this study, two physical rectangular cubic models were constructed to measure the soil moisture advance front. The smaller model was used for experiments with lower discharge and the larger model was used for experiments with higher discharge. The experiments were carried out in four different slopes (0, 10%, 20%, and 30%), three soil types with different textures (light, medium, heavy), with three emitter discharges (2, 4 and 6 liters per hour). The results showed that the moisture distribution (for upstream and downstream of the emitter) was different in sloping lands (for different flow rates and different soil texture). Therefore, in relation to the position of the emitter and plant, drip system should be designed differently in the sloping land in comparison to flat lands. According to the nature of the sloping lands, the plant position was downwardly shifted and its exact positions are suggested for different scenarios (for different discharge rates, slopes, and soils) in this study. The results showed that the percent of downstream wetted radius in sloping lands for the three types of heavy, medium, and light textured soils were between 49.2-81.5%, 49.2-76%, and 48.3-70.7%, respectively. These values for the percent of the upstream wetted radius of the emitter ranged between 18.5-50.8%, 24-50.8%, and 29.3-49.7%, respectively. The results of this study can be used as a general guide in the design of drip irrigation systems in sloping land to determine the plant and emitter position relatively accurately.

This studywas conducted as a completely randomized design with 3 replicates at Research Greenhouse of National Salinity Research Center, during 2017-18 growing season. Treatments were seven levels of water salinity: 3 (control), 10, 20, 30, 40, 50 and 60 dS.m-1. Throughout the experiment, plant length, fresh weight, dry weight, leaf area, chlorophyll content, soluble sugars and proline were measured. Results showed that salinity treatments significantly affected all the traits. Salinity significantly reduced plant height, such that plants in 60 dS/m were 12.37% shorter than those of 3 dS/m. Fresh weight, dry weight, leaf area, chlorophyll a, and total chlorophyll were increased by increasing stress level from 3 to 30 dS/m, but then significantly decreased by increasing salinity up to 60 dS/m. Increasing salinity from 3 to 30 dS/m increased plant dry weight by 3.7 g per plant, but increasing it to 60 dS/m reduced dry weight. Increasing salinity to 60 dS/m led to enhanced proline (52.03%) and soluble sugars (21.21%). Salinity tolerance threshold of Suaeda fruticosa was 31 dS m-1 and the slope of dry matter decrease was 0.22% per increase in each salinity unit.

In this study, the effect of different levels of irrigation water and potassium fertilizer on Roselle was investigated. The experiment was conducted using split plot design with four levels of irrigation water (I1, I2, I3 and I4 equivalent to 40%, 60%, 80%, and 100% crop water requirement) and three levels of potassium (K1, K2 and K3 equivalent 50%, 75%, and 100% potassium requirement) as sub-plot. At the end of experiment, quantitative parameters of plant including height, weight and number of capsules, dry yield, and water use efficiency were measured. Also, qualitative parameters including anthocyanin, protein, and carbohydrate content were measured to investigate the effects of water stress and fertilizer on Roselle quality. The results showed that the simple effects of irrigation water and potassium fertilizer were significant (P <0.01) on all measured parameters. The highest yield was obtained from 100% potassium fertilizer treatments and 80% water requirement. The highest water use efficiency was obtained in 60% water requirement plus 100% potassium fertilizer application, but no significant difference was found between 60% and 80% water requirement. The anthocyanin, protein, and carbohydrate contents increased with decreasing irrigation water depth to 60% of plant water requirement and decreasing potassium fertilizer application. However, there was no significant difference between 50% and 75% K fertilizer application. Therefore, due to the water status of the region and the reduction in water resources, application of 80% water requirement reduces water consumption and 75% potassium fertilizer increases quality and mitigates effect of drought stress in Roselle.

In order to optimize the efficiency of water in agriculture, it is necessary to know the extent of water leakage in the lined canals. In this study, water conveyance efficiency and seepage/leakage losses were determined to evaluate earth and concrete lined channels in Khuzestan irrigation networks. The result of this assessment was to identify the problems of management and damages in these channels. Thirty channels were studied and evaluated in the main irrigation and drainage networks of Khuzestan province, including Karun, North Khuzestan, Karkheh, Shavour and, Zohreh and Jarrahi, and channels managed by the farmers. There were 17 tertiary and quaternary canals and 6 earth channels in irrigation networks, as well as 1 canal and 6 earth channels under farmers’ management. The water conveyance efficiency in canals ranged from 38.9% in Ramshir to 99.7% in Shushtar; and in the earth channels, from 46.9% in Baghmalek to 89.3% in Shush. The comparison of means of the measured and calculated indices was performed by t-test and showed that seepage per km length of the unlined earth canals was 3017.7 m3/day, which had no statistically significant difference with lined canals with a leakage of 2166.2 m3/day/km. The results of Pearson correlation coefficients showed that there was a negative and significant (at p<1%) correlation between distribution efficiency with the amount of seepage per kilometer channel length, and between losses and the input flow rate per km of channel length. Also, 16.7% of the total canals had a water distribution efficiency of less than 67.8% (between 38.9% and 67.8%), while 50% of the canals had a conveyance efficiency of less than 68.6%. The low water losses in half of the concrete lined canals and the excessive water loss in 11% of such canals, which even increased water losses in the earth's channels, reveals the necessity of paying attention to the optimal management of these canals. This optimal management should be considered at the design and construction stages of the structure as well as during the installation in agricultural lands. Attention should also be paid to use of proper seals and other suitable equipment to prevent water leakage.