rasoul asadi; farzad hasanpour; mitra mehrabani; Amin Baghizadeh; Fateme karandish
Abstract
Introduction: In arid and semi-arid areas, water can be a limiting factor for plant growth and agricultural yields. Considering limited water resources in arid and semi-arid climate of Iran, deficit irrigation is one of the strategies for efficient use of water and increasing water use efficiency ...
Read More
Introduction: In arid and semi-arid areas, water can be a limiting factor for plant growth and agricultural yields. Considering limited water resources in arid and semi-arid climate of Iran, deficit irrigation is one of the strategies for efficient use of water and increasing water use efficiency in agricultural lands. Deficit irrigation (DI) is a suitable solution to gain acceptable and economic performance by using minimum amount of water. The Partial Root- zone Drying (PRD) irrigation is a new improvement in deficit irrigation in which the half of the root zone is irrigated alternatively in scheduled irrigation events. The plants with PRD irrigation method can, therefore, have different root system in comparison with other irrigation methods. At this method the plant’s condition would be OK by withdrawing water from wet side, and the roots at the dry side can release abscisic acid hormone which decrease the stomatal conductance and consequently the water use efficiency would increase. Also, by using proper irrigation management in farm, we are able to utilize water, soil and fertilizer to produce high yield and quality products. Drip irrigation is considered one of the most efficient irrigation methods. One of the major advantages is its ability to apply water to the soil as often as desired and in smaller quantity than the other irrigation methods. Drip irrigation has been practiced for many years for its effectiveness in reducing soil surface evaporation and it has been widely used in horticultural crops in both greenhouse and open field.
Materials and Methods: In order to compare two deficit irrigation methods on plant growth characteristics of Rosmarinus officinalis L., a field experiment was carried out during 2016 growing season at an experimental farm in Kerman Municipality seedling production station. The experimental treatments were arranged as randomized complete block design with three replications. The irrigation regimes consisted of full irrigation (FI-100), regulated deficit (RDI75 and RDI55) and partial root zone drying irrigation (PRD75 and PRD55). In this study, drip lines were placed on the soil surface at a distance of 15 cm from the plant and plant rows were placed between drip lines. The irrigation interval was 4 days for all treatments. In the full irrigation and regulated deficit irrigation treatments, the plants were irrigated from two sides for every irrigation. In the PRD, one of two neighboring drip line was alternatively used for irrigation. The irrigation interval was 4 days for all treatments. Dry weight, leaf area index (LAI), number of shoots, plant height, water productivity, root fresh weight, root depth and root volume were measured. Since the highest essential oil of rosemary is at 50 percent of flowering time, the above-mentioned indices were measured at the middle of flowering (190 days after planting) by removing the side rows in each replicate and half a meter from the beginning and end of each row. As a marginal effect, 10 plants were randomly selected and sampled from two middle rows, each replicate of each treatment. The harvested bushes were dried at 25 °C for three weeks and then the dried weight of the vegetative organs was measured. Moreover, the number of 10 plants selected from each treatment was accurately counted to determine the number of shoots. Data were analyzed statistically using SAS Statistical software. Treatment means were compared using LSD test.
Results and Discussion: The results showed that highest herbage dry weight (145.3 g) and leaf area index in different stages of growth were under full irrigation treatment in which no significant difference between this treatment and 75 percent water replacement in partial root zone drying was observed. The highest number of shoots (128.7) and plant height (68.4 cm) were also obtained by full irrigation treatment and there was significant difference between this treatment and other treatments. However, the highest water productivity (2.06 kg/m3), root fresh weight (3.8 g), root depth (16.4 cm) and root volume (2.4 cm3) were found in 75 percent water replacement in partial root zone drying.
Conclusion: According to the results, 75 percent water replacement in partial root zone drying irrigation treatments, in addition to saving water consumption, provides better use of soil moisture and sunlight. Thus, this treatment can be considered as a suitable approach to cope with the water crisis and achieve a sustainable agriculture.
Keywords: Drip irrigation, Drought stress, Leaf area index, Medicinal plant, Rosmarinus officinalis, Water productivity
B. Karimi; N. Karimi
Abstract
Introduction: Among irrigation methods, a drip irrigation system (surface and subsurface) is more acceptable in arid and semi-arid regions due to high water use efficiency and potential crop yield. Pulse drip irrigation (with suitable management practices) is one of the drip irrigation methods (includes ...
Read More
Introduction: Among irrigation methods, a drip irrigation system (surface and subsurface) is more acceptable in arid and semi-arid regions due to high water use efficiency and potential crop yield. Pulse drip irrigation (with suitable management practices) is one of the drip irrigation methods (includes a set of cycles, each cycle consisting of the irrigation phase and a resting phase) that have high potential to improve the uniformity of soil moisture distribution. Suitable design and management of pulse or/and continuous drip irrigation systems substantially require a proper understanding of the moisture distribution pattern around the emitter. One of the critical parameters concerning the moisture distribution pattern, taking into account the wetted area of emitter. Important parameters of the wetted area include the down wetted area (Ad) for the surface and subsurface drip irrigation system as well as the up wetted area of an emitter (Aup) for the subsurface drip irrigation. Modeling the wetted area pattern and considering this parameter in design as one of the criteria for increasing water efficiency in surface and subsurface drip irrigation systems is critical and important.
Materials and Methods: In this research, experiments were carried out in a transparent rectangular cube with dimensions of (3 * 1 * 0.5 m) using three different soil textures (fine, heavy, and medium). The drippers were installed at three different soil depths (surface, 15cm, and 30cm). The emitter discharge was considered 2.4, 4, and 6 lit/hr. Also, these experiments were carried out for two continuous and pulse irrigation systems. In pulse irrigation, the pulse cycles were considered 30-30, 20-40, and 40-20 min. The first number refers to the irrigation time, and the second number refers to the resting time of the system in each cycle. In this research, using a nonlinear regression model, empirical models were developed to predict the wetted area of the moisture front. The input parameters of the suggested model include emitter discharge, saturated hydraulic conductivity, application time, soil bulk density, emitter installation depth, initial soil moisture content, pulse ratio (the ratio of irrigation time to complete period of each cycle) and the proportions of sand, silt and clay in the soil.
Results and Discussion: The results of this study show that the highest and the lowest down wetted area (for surface and subsurface drip irrigation systems) are related to sandy and clay soils, respectively. Also, the highest up wetted area in the subsurface irrigation system is related to loamy and clay soils. The results of the comparison between measured and simulated values of down and up wetted area indicated that these models have acceptable precision and accuracy in estimating the wetted area of the wetting front in surface and subsurface drip irrigation (with pulsed and continuous application). The comparison between the measured and simulated down wetted area of the emitter (for surface drip irrigation with pulsed application) showed that the R2, MAE and RMSE values varied between 0.98-0.99, 0.0027-0.0065 m2 and 0.0034-0.0082 m2, respectively. Concerning statistical values, it is evident that these models have excellent performance in estimation of down and up wetted area for subsurface drip irrigation. For subsurface drip irrigation with the pulsed application, the values of R2, MAE and RMSE for the down wetted area of emitter, ranged 0.91-0.99, 0.002-0.0077 and 0.0032-0.0098, respectively. These models also estimate up wetted areas with less error, and the values of R2, MAE, and RMSE for all treatments varied between 0.89-0.99, 0.0015-0.0067 m2, and 0.0019-0.0077 m2, respectively.
Conclusion: This paper was aimed at presenting relationships for estimating the up and down wetted area of emitter for surface and subsurface drip irrigation (with pulsed and continuous application). Regarding the importance and applicability of empirical models, in this research, nonlinear regression models (NLR, which are more widely used among researchers) were applied. For NLR method, different ten input variables (i.e., emitter discharge, saturated hydraulic conductivity, application time, soil bulk density, emitter installation depth, initial soil moisture content, pulse ratio (the ratio of irrigation time to complete period of each cycle) and the percentage of sand, silt and clay) were considered. The results of this study indicate that the NLR model can estimate the up and down wetted area, and the statistical indices values are within acceptable ranges. Considering these relations in designing surface and subsurface drip irrigation systems can improve the performance of these systems.
T. Raeisinejad; N. Yazdanpanah
Abstract
Introduction: Water has been known as an important limiting factor for plant growth and agricultural yields in arid and semi-arid regions. It is a significant input to agricultural production and also an essential requirement for domestic, industrial and municipal activities. Increasing population and ...
Read More
Introduction: Water has been known as an important limiting factor for plant growth and agricultural yields in arid and semi-arid regions. It is a significant input to agricultural production and also an essential requirement for domestic, industrial and municipal activities. Increasing population and standards of living are contributing to a steep rise in demand for fresh water. By using proper irrigation management practices in farmlands, it is possible to utilize water, soil and fertilizer to produce high yield and quality products. Drip irrigation is considered as one of the most efficient irrigation methods. One of its major advantages is the ability to apply water to the soil as often as desired and in smaller quantity than the other irrigation methods. Two systems of drip irrigation including surface and subsurface drip irrigation methods have been widely used in arid and semiarid regions to reduce the water deficiency impact. Subsurface drip irrigation has been used for many years because of its effectiveness in reducing soil surface evaporation. It has been widely used in horticultural crops under both greenhouse and outdoor field conditions. However, the surface drip irrigation system can be used easier than the subsurface drip irrigation system. In addition, deficit irrigation is one of the strategies for efficient use of water and increasing water use efficiency in agricultural district. Deficit irrigation is a suitable solution to gain acceptable and economic performance by using minimum amount of water. The aim of this study was to evaluate the yield and yield components of sunflower affected by different levels of soil matric potential in combination with two contrasting drip irrigation method i.e. surface and subsurface. In addition, water use efficiency as an important criterion of yield was used to achieve the best and more suitable irrigation method under water scarcity conditions.
Materials and Methods: In order to investigate the irrigation management of sunflower, a field experiment was carried out during 2016 growing season at an experimental farm in Jiroft city. The treatments were laid out in split strip plots based on randomized complete block design with three replications. The treatments were comprised of three soil matric potentials of 40, 55, and 70 centibar for initiation of irrigation in the main plot and sub plots consisted of two drip irrigation systems (surface and subsurface). In the surface systems, drip lines were placed on the soil surface at a distance of 15 cm from the plant and in the subsurface systems, drip lines were placed at a depth of 30 cm. The irrigation time was determined based on the readings of metal tensiometers. These tensiometers were installed in three depths of 15, 30 and 50 cm of soil and at a distance of 20 cm from the plant. In this regard, in both irrigation systems, the mounted tensiometer at a depth of 15 cm of soil was used in the early growth and development, and mounted Tensiometers at depths of 30 and 50 cm soil were used in the middle and final stages of growth. In order to carry out irrigation at the potential point of view, the tensiometers were fully controlled and when the calibrated tensiometer screen showed the desired potential point, irrigation was carried out and the irrigation process continued until the soil moisture reached the crop capacity level. Yield, yield components such as number of seeds per head, along with water use efficiency were measured. Data were statistically analyzed using SAS Statistical software. Treatment means were compared using LSD test.
Results and Discussion: The results showed that the water usage parsimony of 153.6 mm (21.5 percent) between the 40 and 55 c-bar tensions caused that the yield, number of seeds per head and height of plant decreased by 12.5%, 12.8% and 11%, respectively, but water use efficiency increased 10.3%. Compared with 55 c-bar tention, 70 c-bar also decreased the yield, number of seeds per head and height of plant by 33.4%, 22.9% and 22.5%, respectively but increased water use efficiency by 4.7%. Moreover, the yield in subsurface drip irrigation increased by 499 kg/ha compared with surface irrigation. In addition, parsimony of water usage was 10% and water use efficiency increased by 21.5%. Number of seeds per head and the height of plant increased by 8.2% and 8.7%, respectively in subsurface drip irrigation.
Conclusion: According to the results of this study conducted on sunflower in Jirot area, it was concluded that the application of soil matric potential of 55 centibar in subsurface drip irrigation system is the best approach to increase water use efficiency during periods of drought.
Ali Reza Kiani; Afshin Mosavat
Abstract
Introduction: Lack of water and deterioration in the quality of soil and water resources are considered to be the prime cause of reduced crop yield in arid and semi-arid regions ‘More crop per drop’ by trickle irrigation, deficit irrigation, and uncommon water are the best strategies for mitigating ...
Read More
Introduction: Lack of water and deterioration in the quality of soil and water resources are considered to be the prime cause of reduced crop yield in arid and semi-arid regions ‘More crop per drop’ by trickle irrigation, deficit irrigation, and uncommon water are the best strategies for mitigating water crises. Different irrigation management strategies are needed to increase production in different areas. In areas where sufficient water is available, a full irrigation strategy could be a suitable option, while in areas where water is limited, deficit irrigation would be an appropriate method, and finally in areas where water resources are saline, management strategies for achieving sustainable production as well as economic yields would be suitable. Maize is the third most important grain crop in the world following wheat and rice and it is the main source of nutrition for humans and animals. Because of the importance of maize in the world, increasing maize production under environmental stresses is a big challenge for agricultural scientists. Different methods of irrigation and the use of saline water that had satisfactory results for increasing agricultural production have been studied by several investigators . The main objective of this study was to establish an efficient use of limited water resources as well as to explore the possibility of replacing saline water with fresh water using different management techniques.
Materials and Methods: A field experiment was conducted over two maize cropping seasons (2012–2013) in northern Iran (Gorgan Agricultural Research Station) to compare different alternate irrigation scenarios using saline water on corn yield, salinity and soil moisture distribution in a randomized complete block design with three replications. Treatments were: T1 and T2 = 100 and 50 % of crop water requirement with non-saline water, respectively; T3 and T4 = variable and fixed full irrigation with saline and non-saline water in every other row, respectively; T5 and T6= fixed and variable deficit irrigation with non-saline water in every other rows, respectively and T7= full irrigation with saline water. To create the desired water salinity (8 dS/m), non-saline well water (1.5 dS/m) and drainage water (20–35 dS/m) were blended in different proportions. A T-tape drip irrigation system (20 m in length) was used in the field experiment.
Results and Discussion: In general, corn yield in 2013 was about 1270 kg ha-1 higher than in 2012. From the weather records it can be seen that the second year was drier than the first year. Yield analysis showed that deficit irrigation treatments (T2, T5 & T6) and also alternate salinity treatments (T3 & T4) did not significantly difference. In other words, the deficit irrigation management had no effect on yield. Corn yield in T3 and T4 with 50% of saved fresh water was just reduced to 7 and 1 % of T1, respectively. As a result, comparing treatments T3 and T4 with full irrigation have shown that treatments T3 and T4 are the best option. Comparison of moisture distribution in deficit irrigation treatments showed the highest water content in surface and deep layers was related to the treatments T6 and T2, respectively. The distribution of salinity in the soil profile for treatments T3 and T4 showed that after two years of irrigation with saline water, there is the possibility of use saline water for corn production, but drainage and leaching of soil will need to maintain sustainability.
Conclusion: Naturally, in water scarce areas that use some strategic management such as deficit irrigation or saline water use, there is available arable farmland to further develop the irrigated area, and thereby increase total production. According to the results of the two-years where there was a shortage of water to meet crop water requirement and saline water was not available, the use of deficit irrigation managements as described in this study can save fresh water resources and increase total production and farmer's income. If the region is facing a shortage of water resources and saline water is available nearby agricultural land, it is suggested to use alternate furrow irrigation with saline and non-saline water; with the crop water requirement being met by the saline water, the total output will be higher than using deficit irrigation management with non-saline water. Comparision of the distribution of moisture in deficit irrigation treatments showed that surface soil moisture was lower in the treatment of T5 because it was more lateral distribution. In the deeper layers, soil moisture of the treatment T2 was more than others, because it was the predominant infiltration. The two treatments T3 and T4 because of the combined matric and osmotic potential and the movement of water along the sides and deep percolation, resulting widely distributed in soil moisture and thus remaining lower moisture in the soil compare to full irrigation treatments. Consequently, this finding indicates that after two years of corn irrigation using saline (8 dS/m) and non-saline water in every other row (treatments T3 and T4) production can be increased, and in case of proper leaching and drainage management, agricultural sustainability will also preserve.
vahid Moradinasab; mehran shirvani; shamsollah Ayoubi; mohammad reza babaei
Abstract
Introduction: Water shortage in arid and semiarid regions of the world is a cause of serious concerns. The severe water scarcity urges the reuse of treated wastewater effluent and marginal water as a resource for irrigation. Mobarake Steel Complex has been using treated industrial wastewater for drip-irrigation ...
Read More
Introduction: Water shortage in arid and semiarid regions of the world is a cause of serious concerns. The severe water scarcity urges the reuse of treated wastewater effluent and marginal water as a resource for irrigation. Mobarake Steel Complex has been using treated industrial wastewater for drip-irrigation of trees in about 1350 ha of its green space. However, wastewater may contain some amounts of toxic heavy metals, which create problems. Excessive accumulation of heavy metals in agricultural soils through wastewater irrigation may not only result in soil contamination, but also affect food quality and safety. Improper irrigation management, however, can lead to the loss of soil quality through such processes as contamination and salination. Soil quality implies its capacity to sustain biological productivity, maintain environmental quality, and enhance plants, human and animal health. Soil quality assessment is a tool that helps managers to evaluate short-term soil problems and appropriate management strategies for maintaining soil quality in the long time. Mobarakeh Steel Complex has been using treated wastewater for irrigation of green space to combat water shortage and prevent environmental pollution. This study was performed to assess the impact of short- middle, and long-term wastewater irrigation on soil heavy metal concentration in green space of Mobarake Steel complex.
Materials and Methods: The impacts of wastewater irrigation on bioavailable and total heavy metal concentrations in the soils irrigated with treated wastewater for 2, 6 and 18 years as compared to those in soils irrigated with groundwater and un-irrigated soils. Soils were sampled from the wet bulb produced by under-tree sprinklers in three depths (0-20, 20-40 and 40-60 cm). Soil samples were air-dried, and crushed to pass through a 2-mm sieve. Plant-available metal concentrations were extracted from the soil with diethylenetriaminepentaacetic acid-CaCl2-triethanolamine (DTPA-TEA). To determine the total concentration of heavy metals, the soil samples were digested in 6 M HNO3. Concentrations of heavy metals in the extracts were determined by Atomic Absorption Spectroscopy. Finally, available metal micronutrient levels in the soil were compared with the critical deficiency ranges suggested for calcareous soils. Also, total concentrations of the metals in the soils were compared with the standards of the Iranian Environmental Protection Agency to assess possible contamination of soils with heavy metals in the studied area.
Results and discussion: The results of this study showed significant increases of plant-available Fe in the soils irrigated with wastewater for 6 and 18 years as compared to the unplanted control. Regardless of the type of irrigation water used, available Mn and Ni were significantly increased in all forested areas as compared to the unplanted soils. Available Zn fraction was significantly higher in the soils with history of 6 and 18 years of wastewater irrigation. Increase in available Cu concentration was statistically significant only in the soils irrigated with wastewater for 18 years. As the metal concentration in the wastewater used for irrigation was very low, it seems that the major source of metal accumulation in the soils is particulate fallout or emissions directly from the dump sites and metal plating operation. Furthermore, irrigation and forestation practices might have improved bioavailability of micronutrient metals in the soils of green space of Mobarakeh Steel complex through increasing organic matter content of the soils which enhances metal chelation reactions.
Total concentrations of the metals in the forested soils also increased as compared to those of the control. Total Fe, Mn, and Zn concentrations were notably higher in all soils of the green space area as compared to those in the unplanted control sites. Wind-driven particle transport from dumping site to nearby soils may be the main reason for metal build-up in the green space soils. Total concentration of Cu showed no significant difference among the soils of the treatments and the control. Although metal accumulation has been occurring in the soils of the Mobarakeh Steel complex green space, total concentrations in the soils were still considerably lower than the allowable levels recommended by the Iranian Environmental Protection Agency.
Conclusions: The results of this study revealed that metal accumulation has been occurring in the green space soils of the Mobarakeh Steel complex. Considering the short distance of the dumping and metal smelting sites with the green space and very low concentrations of metals in wastewater, in may be concluded that fall out of metallic particles on the soil surfaces from the dumping and smelting sites is the main route for metals accumulation in the soils of the green space areas.
M. Khorramian
Abstract
Introduction: North of the Khouzestan is one of the most important citrus production center. Usually border irrigation is used to irrigate citrus in this area. This system has generally low application efficiency. Several investigations in other arid region have demonstrated in addition to improved irrigation ...
Read More
Introduction: North of the Khouzestan is one of the most important citrus production center. Usually border irrigation is used to irrigate citrus in this area. This system has generally low application efficiency. Several investigations in other arid region have demonstrated in addition to improved irrigation efficiency with low-volume pressurized irrigation systems, citrus trees have adapted with these new irrigation systems. However limited information exists on the performance of mature orchards converted from border surface irrigation to pressurized irrigation systems. Therefore, the current research was conducted to evaluate the feasibility of converting surface irrigation to pressurized irrigation systems on mature citrus trees in climate conditions of North Khouzestan.
Materials and Methods: This study was conducted during three years at Safiabad Agricultural Research Center to evaluate the yield of citrus trees and the quality of fruits for two Marss and Valencia varieties which grow 7 years previously with surface irrigation and converted to pressurized irrigation systems. The treatments consisted of six irrigation methods including Overhead sprinkle irrigation (OHSI), Under tree sprinkle irrigation(UTSI), Trickle irrigation(TI)(six 8 L/h Netafim emitters), Microjet irrigation (MI)(two 180 microjet were located under canopy near of the trunk at opposite sides of trunk),Bubbler irrigation(BI)(a single located under the canopy of each tree)andSurface irrigation(SI) method.Soil texture was clay loam well drained without salinity(ECe=0.69ds m-1), with 1.25 percent organic carbon. The experimental design was completely randomized design. The trees were irrigated during spring and summer seasons. For calculating irrigation water depth in TI, MI and BI systems, daily evaporation from a class A evaporation pan of the Safiabad weather station (nearby the experimental field) was collected, and evapotranspiration of the citrus trees was calculated applying a pan coefficient of 0.8. During the growth season, soil moisture content was measured before irrigation in root zone depth using weighing method at two points of the beginning and the end of the garden to obtain an average showing changes of the field moisture content. Applied water were measured with flow meter for OHSI, UTSI,TI, MI and BI methods and WSC flume for SI treatment. In middle January after fruit ripening, fruit yield was determined by harvesting all the fruits from six trees located in the center of each plot. Weight of fruits from every tree was recorded. Then, 3kilogram fruits per tree were randomly separated and peel thickness, diameter, weight, juice solid percent, total dissolved solids(TSS) and Citric acid were measured.
Results Discussion: The annual precipitation was 385,345, and 336 mm for 2004, 2005, and 2006 years, respectively. The mean temperature of June, July and August (the warmest months) for 2004, 2005, and 2006 was 45.6, 45.2 and 45.8°C. Higher temperature in third year caused to increase heat stress, so fruit yield decreased. Irrigation water consumption in OHSI and UTSI were among 15000 to 17000 m3ha-1. Continues contact of irrigation water contacting with leaves in OHSI causes the accumulation of salts on the leaf surface and leaf drop in harvest season. Consumed water in BI, MI and TI compared with SI method reduced by as much as 48.6%, 57.2%, and 58.4%, respectively. Because soil wetted area in BI, MI and TI methods were low and about 30 to 50 percent of soil area.
There were significant differences in citrus yield, water use efficiency (WUE) and quality in 1% and 5%, so that comparison of means in Mars variety showed that the yield of trees in TI and SI methods were significantly higher than UTSI method. On the other hand, fruit yield was similar in OHSI, MI, TI and SI methods. Valencia variety fruit yield was similar for in BI, MI, TI and SI methods in all 3 years, and significantly more than OHSI and UTSI although BI, MI, TI used only 48% to 58% of irrigation water compared with SI method. WUE under BI, MI and TI methods was enhanced by 2 to 3 times more than SI,OHSI and UTSI methods because consumed water decreased in BI, MI and TI about 50%. Fruit size and fruit weight of Marss variety in the OHSI and fruit size and fruit weight of Valencia variety in the OHSI, MI and SI were better than other systems and had a significant difference in 1% probability.
Conclusion: Overall results of this study indicated that it is possible to convert SI to BI, MI and TI methods in northern khouzestan orchards without decreasing in fruit yield and quality of citrus trees. Salt accumulation on leaf surface in OHSI method was caused to drop leaves in harvest season.
M. Tabei; Saeid Boroomand Nasab; A. Soltani Mohamadi; A. H. Nasrollahi
Abstract
Introduction: The to be limited available water amount from one side and to be increased needs of world population from the other side have caused increase of cultivation for products. For this reason, employing new irrigation ways and using new water resources like using the uncommon water (salty water, ...
Read More
Introduction: The to be limited available water amount from one side and to be increased needs of world population from the other side have caused increase of cultivation for products. For this reason, employing new irrigation ways and using new water resources like using the uncommon water (salty water, water drainage) are two main strategies for regulating water shortage conditions. On the other side, accumulation of salts on the soil surface in dry regions having low rainfall and much evaporation, i.e. an avoidable case. As doing experiment for determining moisture distribution form demands needs a lot of time and conducting desert experiments are costly, stimulator models are suitable alternatives in answering the problem concerning moving and saltiness distribution.
Materials and Methods: In this research, simulation of soil saltiness under drip irrigation was done by the SWAP model and potency of the above model was done in comparison with evaluated relevant results. SWAP model was performed based on measured data in a corn field equipped with drip irrigation system in the farming year 1391-92 in the number one research field in the engineering faculty of water science, ShahidChamran university of Ahvaz and hydraulic parameters of soil obtained from RETC . Statistical model in the form of a random full base plan with four attendants for irrigating water saltiness including salinity S1 (Karoon River water with salinity 3 ds/m as a control treatment), S2 (S1 +0/5), S3 (S1 +1) and S4 (S1 +1/5) dS/m, in 3 repetition and in 3 intervals of 10 cm emitter, 20 cm emitters on the stack, at a depth of 0-90 cm (instead of each 30 cm) from soil surface and intervals of 30, 60 and 90 days after modeling cultiviation was done. The cultivation way was done handheld in plots including four rows of 3 m in distance of 75 cm rows and with denseness of 80 bushes in a hectar. Drip irrigation system was of type strip with space of 20 cm pores.
Results and Discussion: The results of this section of work have shown in the form of chart drawing and calculating identity indices or recognition (R2), maximum error (ME), normalized root mean second error (NRMSE) and coefficient of residual mass (CRM) in the distances on the stack, 10 and 20 cm dropper. The amount of R2, ME, NRMSE and CRM in 10 cm dripper were calculated to be 0/81, 0/46, 11/77 and 0/018 mg/cm3, in 20 cmdripper 0/78, 0/48, 16/44 and 0/1172 mg/cm3 and on the stack 0/75, 2/8, 18/19 and 0/07 mg/cm3. The highest recognition factor was a distance of 10 cm dripper (81 percent) and then reduces to keep distance from dripper recognition factor . This subject is the highest potency close to the dripper. This can happen for less saltiness in the spaces close to the dripper according to drip irrigation features. The high ME amount shows the less attendance computing of the model, it comes to it’s maximum on the stack, however (2/8 mg/cm3), the distances near to the dripper the obtained ME amount shows the good care in estimating soil saltiness. Also, based on being positive CRM parameter amount was seen. It is less in the amount observed in anticipating of saltiness in the anticipated amount. By considering NRMSE factor, higher amount of anticipating is based on observations.
Conclusion: Generally, the results obtained from stimulating of SWAP show that this model can stimulate saltiness distribution in soil under drip irrigation with salty water. This model can be used as useful tools for evaluation of saltiness distribution around the dripper.
M. Khorami; A. Alizadeh; H. Ansari
Abstract
Increased use of drip irrigation systems in the country and farmer's tendency to use more efficient irrigation systems, has caused need to know about parameters and factors that affect irrigation efficiency. This Study was done to examine how water moves in the soil and soil moisturere distribution at ...
Read More
Increased use of drip irrigation systems in the country and farmer's tendency to use more efficient irrigation systems, has caused need to know about parameters and factors that affect irrigation efficiency. This Study was done to examine how water moves in the soil and soil moisturere distribution at Weather Station of Ferdowsi University of Mashhad. Inthisstudy, Hydrus 2D/3D Model performed by using data from laboratory and field analysis. Thes imulation results of soil moistureina 48 hour period were compared with the results offield measurements. The results showed that the model is very capable in simulating moisture contentin thesoil. Statisticalerroranalysiswas described to estimate model parameters using Maximumerror (ME), Root Mean Square Error (RMSE) and Mean Absolute Error (MAE). Based on the results of RMSE parameter in volume tricsoil moisture, forallintervals and all discharges RMSE was less than 10 percent that it shows that model hashigh ability in simulation. Maximum Error was up to 5% of and Mean Absolute Error was up to 2.05 % of volumetric moisture content.
