Showing 29 results for Sepaskhah
F. Heydari, A. Rasoulzadeh, A. R. Sepaskhah, A. Asghari, A. Ghavidel,
Volume 17, Issue 65 (fall 2013)
Abstract
The objective of this study was to evaluate the effects of crop residues management on soil physical and biological properties. The impacts of residue management on yield of forage corn and barley and soil micro-organisms population were also studied. The results showed that application of crop residues increased soil organic matter (22.2 %), saturated hydraulic conductivity (51.9 %), porosity (3.7 %), mean weight diameter (MWD) of the aggregates (5.4 %), and field capacity (5.8 %) and decreased bulk density (3.7 %) Whereas crop residues burring decreased soil organic matter (31.8 %), saturated hydraulic conductivity (36.6 %), porosity (0.5 %), mean weight diameter (MWD) of the aggregates (5.1 %), and field capacity (4.1 %) and increased soil bulk density (1 %). Soil water characteristic curves showed that the observed differences in soil water retention of application and burning residues treatments were higher at low matric suctions than those at high water matric suction. The results demonstrated that micro-organisms population significantly (P<0.05) decreased in residues burning treatment compared with the residues application treatment. Therefore, based on the results of this study residues' burning is not recommended in Ardabil.
M. R. Yazdani, M. Parsinejad, A. R. Sepaskhah, N. Davatgar, S. Araghinejad,
Volume 18, Issue 69 (fall 2014)
Abstract
Intermittent irrigation of paddy fields with long intervals can cause cracks in heavy soils, facilitate loss of water and finally damage the crop. This study was carried out in order to investigate the cracking trend and some other factors affecting soil cracking in four different physiographical areas of paddy field. The study areas were Rasht, Shanderman, Astaneh and Khomam in Guilan province. The experiment was carried out in paddy fields with transplanted rice by determining the physical properties relevant to cracking behavior after irrigation withdrawal in the reproductive stage. Soil analysis showed that despite similarity in type of dominant minerals, the linear expansion coefficients of Rasht and Khomam soils were higher than those of two other areas. In addition, there was a significant relationship between crack dimensions and volumetric soil water content and clay content. Furthermore, the temporal variation in study of crack development (depth, width and density) showed that they varied in different areas and were affected by volumetric soil water content and the groundwater depth. In addition, the depth of cracks in all soils did not reach the hard pan. All the investigated soils showed a definite threshold for width and depth of cracks for 20-25 days after irrigation withdrawal. After this period, specific values for width (about 3.0, 2.0, 2.5, and 5.0 cm) and depth of cracks (20, 25, 17, and 27 cm) were registered for Astaneh, Khomam, Shanderman and Rasht, respectively
M. Noshadi, M. Jamaldini, A. Sepaskhah,
Volume 19, Issue 71 (spring 2015)
Abstract
In this research, the hydraulic behavior of two kinds of envelopes including synthetic envelope, PP450 and gravel envelope with USBR standard in two soil tank models with silty loam texture was investigated. Three water heads including 55, 75 and 105 cm (water logging) from drain level were used. The discharge of pipe drain in the steady state condition for gravel envelope and at 55, 75 and 105 cm water heads was 188.9, 172.0 and 897.0% more than those in PP450, respectively. Envelope hydraulic conductivity rates at gravel envelope for 55, 75 and 105 cm water heads were 24.6, 14.0 and 21.2 times higher than those in PP450, respectively, and gradient ratios in these water heads for gravel envelope were 14.5%, 2.8% and 14.2% lower than those for synthetic envelope. There were also different behaviors in the two kinds of envelopes for hydraulic conductivity and entrance resistance of pipe and envelope in 55 and 75 cm water heads relative to 105 cm. In general, according to the measured parameters in this research, gravel envelope showed a better performance.
M. Omidvar, T. Honar1, M. R. Nikoo, A. R. Sepaskhah,
Volume 20, Issue 76 (Summer 2016)
Abstract
At the river catchments, different strategies at the whole or different parts of the basin can be applied for water resources management. One of these strategies is optimal water allocation and crop pattern. In this study, an optimization model for water allocation and cropping pattern is presented based on the cooperative game theory. To measure the performance of the developed model, the cultivated area of Ordibehesht Canal in the Doroodzan irrigation network has been studied. First, using a fuzzy model and considering the fuzzy coefficients values in the objective function and constraints, the optimal crop pattern and allocated water has been determined for each crop. Second, benefits of stakeholder’s coalitions have been determined by developing a cooperative game model and based on the structure and properties of the irrigation water distribution network and water rights of each part. Then, the total net benefit has been reallocated to the different stakeholder in a rational and equitable way using Least Core games. The results show that by allocating more water to the sectors with more potential production, more profits are generated and water productivity increases. For example when players cooperate together and form the grand coalition, the net benefit increases from 8.906 billion Tomans to 9.724 billion Tomans that show an increase in the economic productivity of water.
Sh. Zand-Parsa, S. Parvizi, A. R. Sepaskhah, M. Mahbod,
Volume 20, Issue 77 (Fall 2016)
Abstract
In agricultural development many factors such as weather conditions, soil, fertilizer, irrigation timing and amount are involved that are necessary to be considered by the plant growth simulation models. Therefore, in this study, the values of soil water content at different depths of soil profile, dry matter production and grain yield of winter wheat were simulated using AquaCrop and WSM models. The irrigation treatments were rain-fed, 0/5, 0/8, 1 and 1/2 times of full irrigation conducted in Agricultral College of Shiraz University during 2009-2010 and 2010-2011. The models were calibrated using measured data in the first year of experiment and validated by the second year data. The accuracy of soil water simulation was used to refer to the accuracy of simulated evapotranspiration. The accuracy of soil water content at different layers of root depth in the validation period was good for the WSM model (Normalized Root Mean Squer Error, NRMSE= 0/14). But the AquaCrop model showed less accuracy for soil water content (NRMSE=0/26). However, the values of predicted and measured crop evapotranspiration were close together at full irrigation treatment, the accuracy of AquaCop predictions was decreased with inceasing water stress. WSM model has had a good estimation of the dry matter and grain yield simulation with NRMSE of 0/15 and 0/18, respectively. However, they were simulated with less accuracy in the AquaCrop model with NRMSE of 0/19 and 0/39.
Sh. Zand-Parsa, S. Parvizi, A. R. Sepaskhah, A. A. Kamgar Haghighi,
Volume 22, Issue 1 (Spring 2018)
Abstract
In this study, the values of moisture and soil temperature were estimated at different depths and times under unsteady conditions by solving the Richards’ equation in an explicit finite difference method provided in Visual Studio C#. For the estimation of soil hydraulic parameters, including av and nv (coefficients of van Genuchten’s equation) and Ks (saturated hydraulic conductivity), soil moisture and temperature at different depths were measured by TDR probes and the stability apparatus, respectively. The objective function [equal to Root Mean Square Error (RMSE)] was minimized by the optimization of a parameter separately, using the Newton-Raphson method, while, the other parameters were considered as the constant values. Then, by replacing the optimized value of this parameter, the same was done for other parameters. The procedure of optimization was iterated until reaching minor changes to the objective function. The results showed that soil hydraulic parameters (coefficients of van Genuchten’s equation) could be optimized by using the SWCT (Soil Water Content and Temperature) model with measuring the soil water content at different depths and meteorological parameters including the minimum and maximum temperature,, air vapor pressure, rainfall and solar radiation. Finally, the measured values of soil moisture and temperature were compared to the depth of 70cm in spring, summer, and autumn of 2015. The values of the normalized RMSE of soil water content were 0.090, 0.096 and 0.056 at the soil depths of 5, 35 and 70 cm, respectively, while the values of the normalized RSME of soil temperatures were 2.000, 1.175 and 1.5 oC at these depths, respectively. In this research, the values of soil hydraulic parameters were compared with other previous models in a wider range of soil moisture varying from saturation to air dry condition, as more preferred in soil researches.
Sh. Zand-Parsa, F. Ghasemi Saadat Abadi, M. Mahbod, A. R. Sepaskhah,
Volume 24, Issue 2 (Summer 2020)
Abstract
Due to the limited water resources and growing population, food security and environmental protection have become a global problem. Increasing water productivity of agricultural products is one of the main solutions to cope with the difficulties. By optimizing applied water and nitrogen fertilizer, the pollution of groundwater could be deceased and the water productivity could be increased. The aim of this research was to determine the relationships between water productivity (IRWP) and water use efficiency (WUE) and different amounts of applied water (irrigation + rain fed) and nitrogen (applied and residual). This study was conducted on wheat (Triticum aestivum L., cv. Shiraz) in Shiraz University School of Agriculture, based on a split-plot design with three replications, in 2009-2010 and 2010-2011 periods. Irrigation treatments varied from zero to 120% of full irrigation depth, and nitrogen fertilizer treatments varied from zero to 138 kg ha-1 under basin irrigation system. The experimental data of the first and second years were used for the calibration and validation of the proposed relationships, respectively. The calibrated equations using the dimensionless ratios of irrigation depth plus rainfall, actual evapotranspiration and nitrogen fertilizer plus soil residual nitrogen to their amounts in full irrigation and maximum fertilizer amounts were appropriate for the estimation of water productivity and water use efficiency. The values of the determination coefficient (R2) for water productivity and water use efficiency (0.88 and 0.93, respectively), and the values of their normalized root mean square error (NRMSE) (0.2 and 0.13, respectively) showed a good accuracy for the estimation of IRWP and WUE.
M. Askari, A. A. Kamgar-Haghighi, A. R. Sepaskhah, F. Razzaghi, M. Rakhshandehroo,
Volume 24, Issue 3 (Fall 2020)
Abstract
In the present study, the effects of different levels of irrigation, organic mulch and planting method on the mungbean yield in Badjgah were investigated. The experimental plan in the first year was full randomized block, while in the second year, it was full randomized split-split plot block design, in three repetitions. The results showed that in the FI treatments, the yield was increased up to 2% for the first year and 5% for the second year by changing the planting method from on over-ridge planting method to the in-furrow planting one. Also, the results of the first year showed that there was no significant difference between the yield in the fully-irrigated treatments without mulch and the treatment with mulch and 0.75 FI. The amount of the irrigation water could be decreased up to 25% by adding organic mulch in both planting methods, as compared to the fully-irrigated treatments without mulch. The maximum water productivity equal to 0.4 kg/m3 was observed in 0.5 FI, in-furrow planting method with mulch treatment. It can be, therefore, concluded that the water productivity may be maximized with the application of both deficit irrigation and mulching strategies.
M.r. Bahadori, F. Razzaghi, A.r. Sepaskhah,
Volume 26, Issue 3 (Fall 2022)
Abstract
Inefficient use of limited water resources, along with increasing population and increasing water demand for food production has severely threatened agricultural water resources. One way to overcome this problem is to improve water productivity by introducing new crops that tolerate water stresses such as quinoa. In this study, the effect of water stress at different stages of plant growth (vegetative, flowering, and grain filling) was studied on plant parameters, yield, and water productivity of quinoa (cv. Titicaca). This study was conducted under field conditions and the treatments were performed as a block experiment in a completely randomized design with four replications. Experimental factors were: treatment without water stress or full irrigation (F) and water stress treatment (D) at 50% of the need for full irrigation at different stages of quinoa growth. The application of deficit irrigation during different stages of plant growth decreased stomatal conductance, leaf area index, leaf water potential, seed yield, and water productivity, while deficit irrigation increased the green canopy temperature. According to the results of the present study, the flowering stage of quinoa was very sensitive to water stress leading to produce lower yield compared with the amount of yield obtained when vegetative and or grain filling stages are under water stress conditions.
