جستجوی مقالات مرتبط با کلیدواژه « Irrigation requirement » در نشریات گروه « آب و خاک »

The Severe shortage of surface and groundwater resources is the most important constraint on sustainable agricultural development in arid and semi-arid regions. Frequent droughts in recent decades have also led to a significant drop in groundwater levels due to uncontrolled abstraction. In the present study, different irrigation scenarios are provided to reduce the withdrawal of water from the aquifer of Kavar plain in Fars province. The results of various studies show that due to climate change, water resources are reduced and irrigation requirements of plants will be increased during the growing season (Goodarzi et al., 2015; Zeinoddini et al., 2019). In this study, to simulate future climate parameters, the outputs of AOGCMs models and emission scenarios RCP2.6, RCP4.5, and RCP8.5 of the Fifth Climate Change Report were used (IPCC,2014). Then irrigation requirements of the study area were calculated by Cropwat software considering the cultivation pattern for the future period. Finally, by defining irrigation scenarios, the simultaneous effects of climate change and cultivation pattern change in the development of irrigation systems (surface and pressurized) on groundwater resources were evaluated.

In this study, a fuzzy multi-objective planning model was used for the optimal allocation of irrigation water and land use under multiple uncertainties. The effect of effective rainfall for determining the irrigation requirement of cultivated crops and also the limitation of surface water and groundwater resources were taken into account in the developed model in the Talash study area, which is located outside the Sefidroud irrigation and drainage network. The study area of Talesh was divided into three irrigation areas: Astara, Talesh, and Rezvanshahr. Then, the results of the optimal model were investigated at different levels of α-cut (0, 0.2, 0.4, 0.6, 0.8, and 1). Allocated amounts of surface water and groundwater showed that maximum shortages occurred in June and July in Talash area, So that the shortage of Talash area in the upper and lower bounds of a-cut=0.8 was 1.7 and 2.7 times more than Astara area as well as 1.2 and 1.8 times more than Rizvanshahr area, respectively. The optimal ratio of groundwater consumption to the total allocated water in Astara, Talesh, and Rezvanshahr areas were 13.4%, 58.1%, and 28.5% respectively. Also, 100% of the allowable groundwater is consumed in most of the dry months of the year. Due to the unavailability of surface water resources to many farmers in this area, proper approaches should be given to the farmers for more access to surface water. Therefore, the results of this study could be a warning for the regional manager and planners to consider this issue in future planning to select the best decision regarding the use of the type of irrigation water resource.

Irrigation should be applied in accordance with an accurate estimate of the crop water requirement and the crop growth stages (Jensen and Allen, 2014). In recent years, several meteorological forecasting models (MFM) have been developed which are capable of forecasting weather data. Such data could be used to calculate and predict crop water requirements during the next few days. The performance of irrigation canals and water delivery systems can be significantly improved if future short-term demands based on the predicted crop water requirement are available. The appropriate performance of these models in the agricultural sector depends on the quality of their predictions of various weather variables. The aim of this study is to evaluate the accuracy of the predicted spring sugar beet water requirement in the Jovien region when 5-day forecasted meteorological variables by ECMWF, GFS, and MeteoBlue MFM were used as the climatological parameters in the Penman-Monteith equation. The prediction accuracy of these models was evaluated under four categories, 1. Inclusion of the three main meteorological variables involved in calculating reference evapotranspiration (ET_0), including maximum air temperature (T_max) and minimum air temperature (T_min), and maximum wind speed, 2. Inclusion of radiation term (ET_0^Rad) and advection term (ET_0^Adv) of the Penman-Monteith equation, 3. Inclusion of ET_0 and water requirement of spring sugar beet.

Meteorological forecasts for ECMWF, GFS, and MeteoBlue databases were obtained from https://www.windy.com. The meteorological variables presented by these models and used in this research were temperature, wind speed, and the degree of cloudiness. The study period was selected from May to December of 2020.ET0 was calculated using the FAO-Penman-Monteith method presented in the FAO 56(Allen et al., 1998). The first part of the FAO-Penman-Monteith (0.408∆(R_n-G)/(∆+γ(1+0.34 u_2 ) )) represents the contribution of the energy terms to the process of evapotranspiration and the second term ((γ 900/(T+273) u_2 (e_s-e_a ))/(∆+γ(1+0.34 u_2 ) )) signifies the importance of advective forces. Meteorological data obtained from the Jovein weather station was checked to take into consideration the possibility of non-standard surface cover surrounding the weather station in accordance with the method recommended in Annex 6 of FAO 56. Crop coefficients in early, developing, middle, and ending growth periods were also calculated based on the method recommended by the FAO 56.

The GFS model had the best performance in estimating T_maxwith the lowest Bias and RMSE errors of 1.4 and 2.3 degrees Celsius, respectively. Also, MeteoBlue with Bias and RMSE values of -2.2 and 1/3, respectively, had the best performance in estimating T_min. All three models underestimated the air temperature. The bias error of GFS, ECMWF, and MeteoBlue models in predicting the maximum daily wind speed in the Jovein region were 0.1, 1.3, and 1.8 m/s, respectively, and their RMSE Respectively 3.3, 3.3, and 3.4 m/s.Since the GFS model estimated Tmean and consequently vapor pressure deficit (VPD) with a higher degree of accuracy as compared with the other model, the advective term (ET_0^Adv) computed using data estimated by the GFS model wasmore accurate than that of the other models. The bias and RMSE errors of this model in estimating the mentioned variable were 0.4 and 0.7 mm per day, respectively. All the other three models underestimated ET_0^Adv.The bias error of GFS, ECMWF, and MeteoBlue models in estimating ET0Rad were -0.4, -0.5, and -0.2 mm/day, respectively, and their RMSE were 0.61, 0.67, and 0.65 mm per day, respectively.When the overestimated ET0Rad and underestimated ET_0^Adv terms were summed up to calculate ET_0 according to the FAO-Penman-Monteith method, the bias error of the outcome (ET_0) was significantly reduced for all the models. The bias error of the ET_0 for the GFS, ECMWF, and Meteoblue models were 0.03, -0.03, and 0.47 mm/day, respectively. Their RMSE values were 0.62, 0.58 and 0.94 mm/day, respectively.K_(c_ini ) of sugar beet for Jovein region with 4-day wetting intervals and light soil texture with an average ET_0 of 5.9 mm/day was 0.56, and K_(c_mid ) and K_(c_end ) were also calculated as 1.176 and 0.676, respectively. The seasonal water requirement of spring sugar beet for the Jovein region was 866 mm. The seasonal water requirements calculated using the outputs of GFS, ECMWF, and Meteoblue were 860, 866, and 788, respectively. However, the cumulative error of these models were 66, 65, and 101 mm, respectively, during the growing season.

A notable result in this study is the interaction of the ET_0^Adv and ET_0^Rad terms, which canceled out each other over and under estimations—all the three models underestimated and overestimated ET_0^Adv and ET_0^Rad terms, respectively. Thus the absolute value of the oblique error of the computed ET_0 was less than that of the ET_0^Adv and ET_0^Rad terms. However, the RMSE of ET_0, which indicates the noise and random behavior of the error sources, was not reduced.

Irrigation management is one of the most important factors affecting the development and expansion of the plant root. The aim of this study was to investigate the effect of different deficit irrigation treatments on the root characteristics of fodder maize (KSC 704) in surface drip irrigation system. This research was conducted in agricultural research center of Khorasan Razavi during the 2014 growing season. A factorial experiment based on randomized complete blocks design with nine treatments and four replications was carried out. Treatments included full irrigation (FI), deficit irrigation (DI) and replacements of 80 and 60% of total water requirement, partial root zone drying (PRD) at 100, 80 and 60% of water requirement and fixed partial root zone drying (FPRD) at 100, 80 and 60% of water requirement. Water requirement was determined based on compensation of soil moisture deficit using an electromagnetic moisture meter. Water was measured by volume meters and distributed in the field. The first stress was applied at the 6-leaf stage of maize. Two weeks after applying the first deficit irrigation treatment in the 10-leaf stage of the plants, the first root sampling performed. Dry weight and volume, lateral and deep penetration of roots were measured at each sampling. The results showed that in all treatments the average amount of all measured traits decreased with decreasing water consumption. There was no significant difference among root dry weight of FI, PRD100 and PRD80 treatments. Root volume was affected by water stress but application of PRD80 method prevented the negative effects of water stress on root volume. Therefore, PRD method is more efficient compared to DI and FPRD methods when applied water stress, and water and nutrients will be absorbed at a higher level by root.

Pistachio production in Iran has a long history. Iran's pistachio quality is unique among the world's producing countries. Increasing water productivity for this strategic product is essential. The water consumed for pistachio in Iran has not been determined. In some parts of the country, researches have been carried out and quantities for pistachio irrigation water application are reported. In order to measure irrigation water application of pistachio under farmers conditions and compare it with water requirement and the national document, this research was conducted from October 2016 for one growing season in some gardens of Khorasan Razavi, Semnan, Kerman and Yazd provinces. In these provinces, 88 gardens were selected and in each of them, irrigation water application (without intervention in their irrigation program), yield, water productivity, and some other parameters were determined. The results showed that water consumption and water productivity in the studied provinces were significantly different. The yields of the gardens of the four provinces were close to each other. The average yield of pistachio, irrigation water application and water productivity were 1764 kg/ha, 8057 m3/ha and 0.26 kg/m3, respectively. The results showed that the amount of water application in all pistachio gardens were less than the nete irrigation water requirement.

Agriculture is directly affected by climate conditions and changes; therefore, it is essential to understand the effects of climate change on agricultural water resources in order to adapt negative effects on sustainable crop production. In this study using three scenarios; RCP2.6, RCP4.5 and RCP8.5 of the HadGEM2-ES climate model, the future climate data (precipitation, minimum and maximum temperatures) for two periods (2020-2039 and 2040-2059) were forecasted under climate change and based on a 20-years basic period (1985-2005) climate data using LARS-WG software. The base-period evapotranspiration was estimated using Hargreaves-Samani method and they were converted to Fao-Penman-Monteith method by Coefficient (G) in order to improve accyracy. According to this, irrigation requirement of rice (most important and major crop in Gilan province) and evapotranspiration were compared between the past and future. Results declared that the average annual maximum and minimum temperatures for the periods of (2020-2039) and (2040-2059) in comparison to the base period, will increase 2.2 and 2.1, 3.2 and 2.8 ˚C respectively. Also, the average monthly rainfall under all three scenarios will increase 11.8 and 13.6 millimeters for the proposed future periods, respectively. In addition, the net irrigation changes of rice for the both proposed periods will increase 0-31% and 0-45%, respectively. The trend of evapotranspiration changes is ascending and the range of changes during the two periods will be 0.4%-13.6% and 6.1%-27.6%, respectively. This method demonstrated the outlook of climate change impacts on irrigation to the farmers. The results of this study suggest that it is necessary to understand climate change impacts on agriculture, for improved agricultural management planning. The results of this study highlight the need to pay more attention to the effects of climate change on reliable agricultural management and planning.

In order to study the effects of deficit and salinity water stresses on aerial and underground organs of Mentha piperita L. two separate experiments were conducted. A randomized complete block design factorial experiment with three replications was designed at 2017-2018 year in a research farm of department of water engineering, campus agriculture and natural resources of Razi University. Water deficit experiment included three levels (100 (Control), 80 and 60% irrigation requirement) and salinity experiment included four levels control (0.9, 2, 3 and 4) dS/m. The results showed that the effect of water deficit stress on aerial characteristics (shoot fresh and dry weight, leaf fresh and dry weight, leaf area and shoot height) and underground organs (root dry weight, root length, root area, volume and density) were significant. The maximum and minimum of leaf dry weight for 100 and 60% of irrigation requirement observed 2.47 and 1.54 grams per plant. With application of 20 and 40% irrigation deficit leaf area in comparison with control 22 and 31% decreased. With application of water irrigation salinity for 2, 3 and 4 dS/m leaf area 15, 20 and 47% decreased. The highest tolerance salinity of Mentha piperita L. was obtained as 3dS/m.

There are new technologies such as geographic information systems (GIS) that can be effective in the optimization of irrigation water. Therefore, utilizing these resources in a desirable, effective and efficient manner to ensure sustainable development is one of the most important issues in the today's world. The aim of this study was to determine and evaluate the potential water use efficiency (WUEp) index in the plain scale by using net water requirement data, area under cultivation and yields, and to determine the comparative advantage of wheat and barley plants in Tehran, Alborz, Qom, Qazvin and Zanjan provinces by employing the geographic information system (GIS). The yields of wheat and barley products by weighted average in ArcGIS software were converted to yields in the plains scale. To calculate the potential and actual water use efficiency, we used the OPTIWAT software in order to calculate the net irrigation water and the current irrigation efficiency plains; also, the yields of wheat and barley products in the plains scale were used. Zoning water use efficiency indexes was performed by using the ArcGIS software and Kriging method. Mapping results showed a comparative advantage of crops in the west and northwest of Tehran province, south and southwest of Alborz province, southwest, north- west and center of Qazvin province, center Qom province and also, northern and southern regions of the Zanjan province, in comparison to other areas. Average potential and actual water use efficiency in the whole study area of the provinces for wheat were 1.43 and 0.58 kg m-3, respectively, while these were 1.62 and 0.65 kg m-3 for barley, respectively.

Proper water management in agricultural fields is largely depends on suitable estimation of evapotranspiration (ET), as a major component of hydrological cycle. The FAO-Penman- montieth method has the ability to provide appropriate estimation of ET, however, due its complexity, using simpler methods is preferred for programming and modeling processes. In this study, using the weather data of the Dasht-e- Naz station in Sari, the capability of 14 methods for estimation daily, monthly and seasonal reference ET was evaluated. These methods included three temperature- based methods, four radiation- based methods, three pan evaporation- based methods and four combined methods. The performance of each method was assessed using statistics including coefficient of determination (R2), root mean square error (RMSE), percent error (PE) and Mean Absolute Deviation (MAD). Investigations showed that the radiation- based equations were more appropriate for estimating ET than other methods. The Irmak (with R2=0.87 and RMSE=5.77 mm d-1) and Ritchi (with R2=0.93 and RMSE=12.59 mm d-1) methods were the best methods with the highest accuracy in the autumn and winter seasons. In the spring, the use of the FAO-24 Pen (with an average error of 0.5 mm) and Rohwer (with an average error of 6.8 mm) (equations are recommended for spring and summer. Based on the results, the Irmak, FAO-24-Radiation, Ritchie, Priestley-Taylor and Blaney-Cridlle methods were five best methods in the study area.

Irrigation scheduling of field and horticulture plants is very important for optimizing consumption of agricultural water. This experiment was carried out for determining irrigation interval and depth of Barhee date in vegetative growth phase during two years. The treatments of irrigation interval were 50, 75 and 100 mm after evaporation from class A pan and the treatments of irrigation depth were 60%, 80%, 100% and 120% evaporation from class A pan. The results showed that effect of irrigation interval, irrigation depth and their interaction were significance on establishment and vegetative characteristics of date offshoot. The minimum of establishment and vegetative characteristics was in irrigation interval of 100 mm after evaporation from class A pan and irrigation depth of 60% evaporation from class A pan. The establishment percent and vegetative characteristics showed that suitable irrigation scheduling for Barhee date offshoots was irrigation interval of 75 mm after evaporation from class A pan and irrigation depth of 80% evaporation from class A pan. The net irrigation requrement were 1716.3 and 2702.3 m3/hectare in frist and second years, respectively.

Wheat is one of the most important product in Fars province and accurate irrigationscheduling causes to increase irrigation efficiency and optimal use of water resources. Because، most of rain events occurs during wheat growing period in Fars province، irrigation of winter wheat is important. Therefore، in this study، a simple daily rainfall generator model with two components was used. Stochastic output of this model coupled to a water balance model that used average deterministic ETp values. Irrigation dates and amountsat 32 climatologically stations in Fars province were determined. The model was based on daily water balance approach and used crop and soil data as input. In the next step، a predictive irrigation schedule at selected probability level for irrigation dates developed with Arc GIS. Finally، spatial maps of simulated values under same probability level was drawn. Because wheat is most sensitive to water stress during critical stages of booting and two weeks before pollination، predictive scheduling does not lead to water stress. The results showed that number of irrigation in southern، west southern and east southern stations in Fars province is higher. Under 75 probability also the highest irrigation requirement was predicted in southern and east southern station. Analyzing the result of model according to certain risk level، is helpful in determining irrigation requirement ofwinter wheat and water resources strategies in Fars province.

Considering the limited water resources, optimum use of water is necessary in Iran. Good management practices and applying advanced techniques to maintain soil moisture and storage, increased water holding capacity and preventing deep percolation are effective methods to increase water use efficiency and improve water resources utilization in the country. Application of superabsorbent polymers is a proper method to enhance water and increase soil water holding capacity. In this research the effect of superabsorbent polymer on the tomato yield and its water productivity was evaluated in the greenhouse. Trial was conducted using factorial experiment with a completely randomized design layout in which the treatments were three irrigation regimes (including 75 (low irrigation), 100 (full irrigation) and 125 (more irrigation) percent of crop water requirement) and four superabsorbent hydrogel application of 0, 4, 6, 8 and 10 grams per kilogram of pots soil in four replicates. The results showed that irrigation and superabsorbent are effective on yield and water use efficiency and application of 6 g superabsorbent hydrogel per kilogram of soil in 125 %irrigation level had significant effect on tomato yield and its water productivity compared to control (100% of crop water requirement and 0 g superabsorbent per kilogram of pots soil). Therefore mentioned condition is recommended to have maximum tomato yield and its water productivity.

To investigate the effects of different irrigation levels on yield and oil content of rapeseed, and to determine the irrigation requirement and irrigation scheduling, an experiment with Randomized Complete Block Design consisting of four irrigation treatments replicated 3 times, was conducted in Zarghan Agric. Expt. Station during the years of 2000-2003. The treatments were based on the cumulative evaporation values of 50, 75,100 and 125 mm from class A pan (T50, T75, T100 and T125). The depth of water for each treatment was determined according to the deficit of field capacity and soil moisture content before irrigation. In the three years of experiment, the cultivars: Okapi, Orient and Likord were cultivated and the annual data related to yield and seed oil contents of each cultivar was analyzed separately. In the first year of experiment, the effect of different treatments on yield of Okapi cultivar was not significant, but the maximum and minimum yields were obtained at the T75 and T100 treatments equal to 2678 and 2050 kg ha-1, respectively. The effect of different treatments on seed oil content was significant at the level of 5 %, and the maximum and minimum seed oil contents were obtained at the T100 and T75 treatments equal to 42.50 and 41.66 %, respectively. In the second year of experiment, the effect of different treatments on the yield of Orient cultivar was significant at the level of 5 %, and the maximum and minimum yields were obtained at the T50 and T125 treatments equal to 3133 and 2133 kg ha-1, respectively. The effect of different treatments on seed oil content was significant at the level of 5 %, and the maximum and minimum seed oil contents were obtained at the T75 and T50 treatments equal to 46.38 and 44.82 %, respectively. In the third year of experiment, the effect of different treatments on the yield of Likord cultivar was significant at the level of 5 %, and the maximum and minimum yields were obtained at the T50 and T125 treatments equal to 3667 and 2250 kg ha-1, respectively. The effect of different treatments on seed oil content was significant at the level of 1 %, and the maximum and minimum seed oil contents were obtained at the T50 and T125 treatments equal to 47.63 and 44.60 %, respectively. Also, the best irrigation frequency for the three rapeseed cultivars in the Zarghan area was obtained equal to 10 to 12 days.