جستجوی مقالات مرتبط با کلیدواژه "پنمن مانتیث" در نشریات گروه "کشاورزی"

Accurate estimation of crop water requirement is important especially in arid and semiarid climates. The rate of evapotranspiration can be measured by a lysimeter, however, it is expensive and its measurement is a cumbersome practice and time consuming. Therefore, many researchers use empirical models instead of direct measurements. Evapotranspiration of every crop is related directly to reference crop evapotranspiration (ET0). There are many empirical models for estimation of ET0. Among them the FAO-56 Penman-Monteith (FAO56PM) is known as the standard method in every climate. However, this method needs more climatic parameters which are not available everywhere. Therefore, identification of the model which needs less parameters and easily available climatic parameters will be useful. In this study three candidate models which had such conditions considered. These three models are i) Blaney-Criddle (BC), ii) Doorenbos and Pruitt (DP), and iii) Turk. The suitability of the candidate models compared with the output of the FAO56PM method. The main objective of this study is finding the most suitable model among the three candidate methods in Urmia Lake basin.

The region under study is the Urmia Lake basin located in North West of Iran. Nine stations selected across the basin. Meteorological data gathered from the Islamic Republic of Iran Meteorological Office (IRIMO). The method used here as a bench mark for evaluation of other empirical models is FAO-56 Penman-Monteith (FAO56PM). Three empirical models for ET0 estimation which need less climatic parameters are i) Blaney-Criddle, ii) Doorenbos and Pruit, and iii) Turk. These three models need climatidata that are easily available at least in the region. The recommended form of the FAO56PM method is as follows:ET_0=(0.484×Δ(R_(n-) G)+ϒ 900/(T+273) u_2 (e_s-e_a))/(Δ+ϒ(1+0.34u_2)) (mm day-1) [1] Where Rn is the net solar radiation (MJ/m2/day), G is the ground heat flux (MJ/m2/day), T is mean daily air temperature (℃), u2 is the wind speed at two- meter height (m/s), es is the saturated vapor pressure (kPa), ea actual vapor pressure (kPa). Other parameters explained in Allen et al. (1998).The first empirical candidate model for estimation of ET0 is the Turk model (Shuttleworth 1993) which reads:ET0 =0.31 T/(T+15)(S_n+2.09)(1+(50-RH)/70 ) ( 〖mm day〗^(-1) ) ,if RH<50% [2] Where Sn is the net solar radiation in (MJ/m2/day), RH is the relative humidity (%). If the average RH of a station is great or equal to 50%, then the second parenthesis will be removed from the equation, i.e. its value will be unity. The second empirical candidate model for estimation of ET0 is the Doorenbos and Pruitt (DP) model (Shuttleworth 1993) which reads:ET0 =-0.3+b_dp Δ/(Δ+γ) S_n 〖(mm day〗^(-1)) [3] where bdp calculated from the following relationship:b_dp= 1.066-0.0013 (〖RH〗_mean)+0.045 (U_d)-0.0002 (〖RH〗_mean)(U_d)-0.000315〖(〖RH〗_mean)〗^2-0.0011(〖U_d)〗^2 [4] The third empirical candidate model for estimation of ET0 is the Blaney-Criddle (BC) model (Fooladmand and Ahmadi 2009) which reads:ET0=(a_BC+b_BC f) ) 〖mm day〗^(-1)) [5] Where f=P(0.46T+8.13) [6] and a_BC= 0.0043〖RH〗_min - (n/N)- 1.41 [7] b_BC= 0.82-0.0041 (〖RH〗_min) + 1.07(n/N) + 0.066(U_d) -0.006(〖RH〗_min) (n/N) - 0.0006 (〖RH〗_min) (〖RH〗_min) (U_d [8] In [7] and [8] n is the actual sunshine hours and N is the maximum daily sunshine hours.In order to evaluate the models performances three criteria were used in this study which are i) coefficient of determination (R2), ii) root mean square error (RMSE), and mean absolute error (MAE). The output of models compared with that of the FAO56PM output in each of the selected stations.

Results showed that the median of R2 values of the Turk and BC were great than DP. The median of R2 values of both the Turk and BC were about 0.9. However, this measure for DP was about 0.75. The variance of R2 values in the case of BC was less than DP. The lowest value of RMSE belonged to the BC model which was about 2 mm/day. This value for other two models were more than 2 mm/day. The variance of RMSE obtained for all the nine stations was minimum comparing the three models. Therefore, according to Fig. 3, it can be suggested that when the RMSE was used for selection of the best model then the TURK model was superior than the others. However, when we considered all the three criteria for model selection, then the TURK model was superior than the others. According to Fig. 6 it can be concluded that in summer hot days the DP model overestimate the ET0 comparing the FAo56PM at Tabriz station. However, in the winter cold days DP underestimated the ET0 comparing the FAo56PM at the same station.

In this study three candidate models compared with the base model i.e. FAO56PM. Nine stations around the Urmia lake selected. Results indicated that the TURK model was suitable for ET0 estimation in Urmia Lake basin. This model only need three weather parameters which are i) Tmean, ii) actual sunshine hours (n), and relative humidity (RH). Logical use of fresh water in this basin is recommended.

Figs are one of the main horticultural products in Iran due to their high nutritional value, high yield and economic value, and resistance to adverse climatic conditions. About one million tons of figs are produced annually in the world, Iran is the fifth largest producer of this product in the world (FAO, 2018). In addition to the above, the agricultural sector in Iran, like many countries, is the main consumer of water from renewable water sources. But there are not exact information on the volume of irrigation applied water and water productivity of this product in Iran. Therefore, this study was conducted with the aim of measurement of applied water at field scale and evaluation of water productivity of figs orchards at selected provinces in Iran.

Appropriate estimation of reference evapotranspiration (ET0) has always been challengeas the fundamental parameter to estimate crop water requirement (ETc) in places with a data limitation forresearchers of soil and water resources.In this research, (ET0) had been estimated using the ERA5 reanalysis dataset and the by Penman–Monteith FAO-56 (PM). In the next step, the result was evaluated at the location of meteorological stations in the catchment of Karoon.Climatic data to compute the (ET0) from 26 synoptic meteorological stations of the basin and ERA5 dataset were obtained. Then, daily ET0 were calculated from 1390 to 1400.At first, variables including Tmax, Tmean, Tdew, Tmin, solar radiation, and wind speed were compared with the data of the meteorological station.The results showed that, the ERA5 dataset showed provide reliable temperature parameters and solar radiation estimates (i.e., normalized root mean square error (nRMSE) of < 30%)at the majority of cases. Although this dataset showed high nRMSE in all stations for wind speed values. These comparison between ET0 from observation and ERA5 dataset shown that at the 17 station from 26 station nRMSE less than 30 percent. Overall, the use of ERA5 dataset and estimation of ET0 in places that are faced with data scarcityfor decision- making in new planning can be a useful and reliable tool.

It is necessary to study of water productivity of pomegranate orchards because of limited water resources, need to improve water productivity and the importance of pomegranate fruit. In this study, the volume of applied water and pomegranate yield in more than 120 selected orchards in the provinces of Isfahan, Khorasan Razavi, Markazi, Semnan, Yazd and Fars were measured. Analysis of variance was used to investigate the possible differences in yield, applied water and water productivity. Results showed that except for yield, the difference in the applied water and water productivity was significant. The average yield of pomegranate was 21.5 ton/ha. The average volume of applied irrigation water was 14792 m3/ha. The average productivity of applied irrigation water was 1.69 kg/m3. The average water + effective long-term rainfall productivity was 1.47 kg/m3. The productivity of water + effective rainfall of the current year was 1.43 kg/m3. The volume of applied water in pomegranate orchards and the gross water requirement was not similar in the selected provinces. In some provinces such as Fars, Khorasan Razavi, Semnan and Markazi, the volume of applied water was less than the gross water requirement and in Isfahan and Yazd provinces was more than the gross water requirement. But on average, the volume of applied irrigation water was close to the gross water requirement in the year of the research and to the long-term gross water requirement. The average volume of applied water in drip and surface irrigation systems was 9981 and 15765 m3/ha, respectively, the percentage of reduction of applied water in drip irrigation system compared to surface irrigation was 37%.

Evapotranspiration is a complex phenomenon that depends on many factors and data, so determining it is very difficult and costly. In most methods mainly aimed at estimating evapotranspiration, point measurements have been used to estimate this variable. Therefore, it is only suitable on a local scale and cannot be extended to large basins due to the dynamics and regional changes of evapotranspiration (ET). One of the remote sensing algorithms for estimating real evapotranspiration is the Surface Energy Balance Algorithms for Land (SEBAL). In this algorithm, by estimating all energy components on the land surface such as pure radiation flux, soil heat flux, and tangible heat flux, using the energy balance equation, evapotranspiration is used. The aim of this study is to compare the estimation of real evapotranspiration using SEBAL algorithm in wheat and rapeseed crops with the results of estimating evapotranspiration by Penman-Monteith-FAO method in the field of Esmaeil Abad Agricultural Research Station in 2019-2020. Single-sample T-test of ground surface temperature reflection index showed that the spectral reflection of wheat and rapeseed crops during phenological growth period had a significant difference. The results showed that the computational values of the two models are relatively good and the mean value of square root of error (RMSE) in estimating real evapotranspiration for wheat and rapeseed plants was 3.04 and 2.09 mm/day, respectively, and the coefficient of explanation (R2) was 0.78 and 0.81, respectively. The results showed that SEBAL algorithm model in comparison with Penman-Monteith-FAO model (based on up-to-date meteorological data) The amount of evapotranspiration for wheat and rapeseed plants is lower.

Volumetric delivery of water by installing smart water meters on the agricultural wells could be an effective action for proper use of water and increase the water productivity. In recent years, the smart water meters were used at Arsenjan plain in Fars province for volumetric water delivery.

In this study, the applied water and the water productivity in some of the Arsenjan plain farms and gardens were evaluated. Twelve farms were selected for each of the three products; winter wheat, tomato and pomegranate. Well discharge, crop yield, volume of applied water was measured using smart meters. The actual values were also measured. The values of irrigation water productivity and total water productivity was calculated. The differences between applied water and some water requirement scenarios were compared using t-test.

Results showed that the values of applied water and discharge in the smart meters were 21 and 25 percent less than the actual measured values, respectively. Therefore, the performance accuracy of the studied smart water meters was low. The average irrigation water productivity of wheat, tomato and pomegranate was 0.93, 7.75 and 1.44 kg/m3, respectively. The average applied water in the studied farms and gardens were 43 percent more than the required values estimated by Penman-Montieth method. Finally, it was suggested that in order to improve the performance of smart meters, the calibration of these meters should be considered more carefully.

Achieving food and water security is one of the most important goals of policymakers in different countries. Water scarcity in Iran could be one of the major food security challenges in the future. For this purpose, climatic zoning was performed using the Domarten method. After calculating the water requirement using CROPWAT software; the amount of virtual water, water footprint, water productivity, volume of water consumed by each crop in each zone and the optimal food gap in different climates were calculated. According to the results; The per capita water footprint of the agricultural sector in hyper-arid, desert arid, semi-arid, Mediterranean and humid climates and Iran is 1611.97, 1228.09, 665.83, 884.01, 600.21 and 998.20cubic meters, respectively. In addition, the intensity of water consumption within the 5 climatic zones and Iran is 64.89, 88.03, 63.19, 41.01, 56.38 and 65.48 %, respectively. Net virtual water imports for each zone show that desert arid and humid zones are exporters of virtual water and hyper-arid, semi-arid and Mediterranean zones are importers of virtual water. The results show a contradiction between the realization of water security and food security in terms of quantity. The results showed that if the goal is to establish water security; by increasing the net import of virtual water (in the case of high-consumption products with low water efficiency), the intensity of pressure on domestic water resources in each area could be reduced. But if the goal is self-sufficiency; If the current situation does not change (crop composition in cropping pattern, yield and irrigation efficiency in each zone), more pressure will be put on water resources. Therefore, in order to achieve the goals of self-sufficiency and water security coefficients at the same time; It is recommended to increase the yield, improve the irrigation efficiency, formulate a suitable cultivation pattern and allocate water resources according to water productivity and its yield in each zone.

Rice is one of the most important plants, which grows in different provinces located in north, south and western parts of Iran through a high level of flooding surface irrigation systems with low efficiency. On the other hand, suitable irrigation management programming and the awareness of crop coefficients and exactly, the water requirement of different varieties of this crop is essential in different plant stages. This study was conducted to determine the crop coefficients of rice (Amberbo cultivar) during years 2017 and 2018. For this purpose, water balance drainable lysimeters with a diameter and height of 1.20m and 1.40m were used in farm and glasshouse condition, separately. In this regard, the Penman-Monteith equation for potential evapotranspiration and water balance equation to measure actual evapotranspiration were used to calculate potential evapotranspiration. Finally, the average values of crop water requirement and Ambarbo rice crop coefficients were determined in non-flooding condition for different initial, development, middle, and end stages in the farm and glasshouse condition as (584.59 mm, 0.96, 1.07, 1.25, and 0.95) and (616.28 mm,1.00,1.10,1.29, and 1.05), respectively. The results of this research showed that a lot of rice irrigation water could be saved under Non-Flooding Irrigation Conditions. Therefore, with the saved water, more lands will be cultivated and more production, income and jobs will be provided for the villagers.

Grapes is one of the most important horticultural products in terms of cultivation area, economic and high nutritional values. Iran with an annual production of 2.8 million tons, is among the top countries in the production of grape product in the world. However, there are not accurate information on the volume of irrigation applied water and water productivity of this product in Iran. Therefore, this study was conducted with the aim of measurement of applied water at field scale and evaluation of water productivity of grape in vineyards farms at different hubs of this crop production in Iran.

The volume of irrigation water provided by gardeners in 164 vineyards were measured in the provinces of Qazvin, Fars, Khorasan-Razavi, Zanjan, West Azarbaijan, East Azarbaijan, Hamedan, Markazi, Northern Khorasan, and Semnan as hubs of this product. These hubs covered about 80 percent of the irrigated vineyard cultivated areas. In each hub, 1-4 cities with the highest area under vineyard cultivation were selected for evaluation. The measurements were carried out in different irrigation and planting methods, various soils, different salinity of irrigation water and soil and different grape varieties during the growing season of 2018-2019 without interfering with the farmer's irrigation program. The measured values were compared with the net irrigation water requirement estimated by the Penman-Monteith method using the last 10 years meteorological data and also with the national water document values. Crop yield was recorded at the end of the growing season and water productivity was calucated as the ratio of yield to total water (irrigation applied water and effective rainfall). Analysis of variance was used to investigate the possible difference between applied water and water efficiency among the hubs. Data adequacy was assessed by using the method prposed by Sarmad et al. (2001).

The results showed that the average of applied water and water productivity among the hubs were significant at 1% probability level. The applied irrigation water used in the vineyards and water productivity were 6669 m3/ha and 2.63 kg/m3, respectively. Drip irrigation was about 20% effective compared with surface irrigation in reducing the applied irrigation water in the studied vineyards. Water productivity in drip irrigation orchards was essentially the same as surface irrigation and was not statistically significant. The reason was the lack of proper use and utilization of modern irrigation methods.The average net irrigation water requirement in the study areas estimated by the Penman-Monteith method using meteorological data for the last 10 years as well as the national water document were 6645 and 6456 m3/ha, respectively. The range of irrigation application efficiency in the studied vineyards was from 68 to 100 and its average was 89%. Comparison of applied water and net irrigation requirement indicated deficit irrigation due to water shortage in vineyards of most hubs. In total, 31% deficit irrigation occurred in the studied vineyards, which is a threat to soil salinity and destruction of soil structure in long-term. Grape planting method had a significant effect on reducing the applied water, increasing grape yield and consequently water productivity. Scaffolding method had a positive and significant effect on all studied indices in comparison with the crawling/reptile planting method. It caused a decrease of about 15% in applied water, an increase of 41% in yield and 37% in crop water productivity.

Due to the fact that vineyards are faced with deficit irrigation and water stress, training the farmers about the accurate and scientific methods of deficit irrigation in the vineyards can be effective to reduce the destructive side effects of water stress. Due to the widespread use of surface irrigation in the vineyards, training and application of methods to improve surface irrigation performance (evaporation reduction methods, using low pressure methods such as gated pipes, mulching, etc.), to increase irrigation efficiency and to reduce irrigation water applied is recommended. Changing traditional planting methods from crawling/reptile to scaffolding and surface irrigation (qana) to furrow, in addition to reducing evaporation, are the effective ways to increase the yield of vineyards and water productivity.

Evaluation of evapotranspiration is one way to prevent water loss and water resource management. Therefore, in this study, an attempt has been made to calculate the actual evapotranspiration rate in the east of East Azerbaijan province using the SEBAL algorithm. For this purpose, first, based on two Landsat 8 satellite images dated 2017/08/22 and 2017/08/09, the values of Net radiation, soil heat flux, and sensible heat flux are estimated. Then, based on the difference, the amount of instantaneous heat flux was calculated and 24-hour evapotranspiration was obtained for each image. Finally, the amount was compared with the values obtained from the Penman-Monteith method. Also, for processing and analyzing images ENVI4.8 software was used. The results indicated that the amount of evapotranspiration in the Penman-Monteith and SEBAL method on 2017/08/22 was about 6.15 and 7 mm per day, and on 2018/08/09, respectively, about 7.38 for Penman-Monty and 7.94 mm per day for SEBAL. Overall, the amounts of SEBAL actual evapotranspiration and Penman-Monteith potential evapotranspiration have a mean absolute difference (MAD) 0.705 mm per day which indicates that the estimated values are consistent with the SEBAL algorithm and the Penman-Monteith method.

To determine crop coefficient and evapotranspiration of Thymus daenensis Celak., an experiment was performed in 2016 using lysimeters (direct method) and computational method In the direct method, drainage lysimeters with underground structures located at Alborz Research Station in Karaj were used. Each of the lysimeters were 0.9 meters in diameter and 1.28 meters high. In each lysimeter, a seedling of Thymus was planted. Then, two main lysimeters were selected and their irrigation was adjusted to the field capacity. On both sides of the main lysimeters, similar lysimeters were considered as margins. During the experiment period, the input and output water of the lysimeters as well as dry weight of aerial parts, the amount of  evapotranspiration, and water use  efficiency in Thymus daenensis were measured. In order to estimate the evapotranspiration of the reference plant, the computational methods of Blaney Criddle and FAO Penman-Monteith were used. Thymus plant coefficients during plant growth, was obtained as the ratio of Thymus evapotranspiration to reference plant evapotranspiration. Based on the results, the amount of cumulative evapotranspiration of the reference plant by Blaney Criddle-FAO and Penman-Monteith-FAO were 715 and 631 mm, respectively. In lysimeters, Thymus evapotranspiration up to the beginning of flowering was 100 mm, to the beginning of seed production  455 mm, and to the end of seed production  622.13 mm. The Thymus plant coefficients in initial, crop development, mid-season and late-season stages were 0.33, 0.65, 1.20, and 0.99, respectively. Water use efficiency was estimated to be 0.4 gL-1. By determining the plant coefficient and water requirement of Thymus, in addition to helping in design of intelligent systems and mechanized irrigation, it will be possible to plan and manage irrigation during the plant growth period.

Considering the current and prospect situation of Urmia Lake, the future study of variables of irrigation scheduling and management is one of the priorities of agricultural research to improve the cropping pattern in the east of lake. In this study, the time series of wheat evapotranspiration in sixteen regions of East Azarbaijan located at the east of Urmia Lake was determined using the Penman-Monteith FAO method with the regional crop coefficient. The analysis period was 80 years from 1330-31 to 1396-97, which 50 years (from1330-31 to 1379-80) was applied for the time series modeling, 17 years ( from 1380-81 to 1396-97) for testing and 13 years (from 1397-98 to 1409-1410) for future studying up to 1410. Among the eighteen possible models, the appropriate time series model for wheat evapotranspiration in cold climate regions such as Azarshahr, Osko, Bonab, Tabriz, Jolfa, Maragheh, Malekan, Marand and Miyaneh was acquired as ARIMA (0, 1, 1) and for very cold climates such as Ahar, Bostanabad, Sarab, Shabestar, Kaleibar, Harris and Hashtrood was obtained as an exponential trend model. The wheat evapotranspiration in East Azerbaijan in the past 67 years averaged 478 mm and for the next 13 years averaged 500 mm. The findings of this study are valuable and practical for irrigation scheduling in full and deficit irrigated conditions and reduction of drought damage in east Urmia Lake.

Estimation of reference evapotranspiration (ET0) is essential to determine water requirements of crops. In other words, to regionalize ET0 to a large area, some interpolation methods should be used (Goovaerts, 1997). A key parameter which may influence the proper performance of interpolattion methods, is the sequence of ET0 estimation process (Mardikis et al., 2005; Vilanova et al., 2012). That is why using some auxillary variables cross correlated with the main variable, could significantly improve the accuracy of interpolation methods. Therefore, this study aims to analyze the estimation process sequences while investigating spatial variability of annual and monthly ET0 in Iran. A comprehensive comparison of spatial interpolators is performed. Elevation is also used as a secondary variable in multivariate methods.

Accurate estimation of evapotranspiration is one of the most important issues in water balance calculation at the catchment and field scale. The lack of meteorological observations for using empirical methods and the high costs of measuring evapotranspiration using lysimeter restricts the usability of these methods in most cases. To tackle these problems, this research addressed the performance of reanalysis models including W3RA, HBV-SIMREG, PCR-GLOBW, WATER-GAP, and Ensemble for estimation of evapotranspiration at different climate regions of Iran. Besides, the reference evapotranspiration for assessment of the above models obtained using lysimeter measurements. Findings showed that in most cases studies the Ensemble model’s performance with the RMSE value ranges from 3.42 to 7.57 mm/day is the weakest one, while the results of HBV-SIMREG and W3RA show the best agreements with lysimeter dataset. Analyzing the outputs based on mean bias error (MBE) depicted that the estimated evapotranspiration based on W3RA and Ensemble have the minimum and maximum bias, respectively. As an overall conclusion, although results indicate that PCR-GLOBW has the maximum correlation coefficient (CC) with the reference datasets, HBV-SIMREG is the best and reliable model for estimation of evapotranspiration in most climate regions of Iran and can be considered as an alternative dataset, especially in data-limited areas.

Climate change is an effective phenomenon on many natural processes, including hydrologic cycle. The evapotranspiration as one of the parts of the hydrologic cycle will be at the forefront of these changes. Due to the importance of evapotranspiration in water resources management and agricultural planning, the present study was conducted to investigate the effect of climate change on this parameter in Moghan Plain. For this purpose, the HadGEM2 atmospheric and oceanic circulation model was used under RCPS and Lars-WG6 downscaling in 2011-2030 and 2030-2060 periods. Also, Penman-Monteith and Hargreaves-Samani methods were used to calculate evapotranspiration. This study showed an increase of 6 to 8.4% of calculated evapotranspiration with Penman-Monteith method in each of the scenarios in 2030-2011 and 2030-2060 periods compared to the observed years. Also, calculated evapotranspiration of the Hargreaves-Samani method will increase from 4.5 to 7.7% in each scenario in 2030-2011 and 2030-2030 periods compared to the observation years. These increases affects on water demands of Moghan and Khodafarin irrigation and drainage networks in the maximum months, which requires appropriate solutions to adapt to climate change conditions.

Estimation of reference evapotranspiration is one of the important components of water balance in each region and that is one of the effective factors in proper irrigation planning for improving water use efficiency. Among the methods that allow the estimation of variables on a regional scale, two methods of geostatistics and Theissen have key roles for land interpolation in extensive level. This study was conducted in Hamadan province. The best variograms was determined, which were the best fit for the exponential model in Kriging method. In the Theissen method's internal analysis, large values of errors are expanded for those stations located in the north-west and south regions, and the range of error variations is between 0.5% to 16%. But in the Kriging method, these errors are distributed in the north-west and south-west regions, while this method estimated better than Theissen's method, and the range of error variations is between 0% to 12%. Comparison of geostatistics and Theissen interpolation methods showed that in the scale of the seasonal, the geostatistical methods have a higher accuracy, but on an annual scale considering the ease of using the Theissen method, taking into account the accuracy required, there is the possibility of using Theissen's method.

The recent drought and the decrease in the ground and surface water resources of the country have raised a change in the surface irrigation methods to new irrigation methods as a useful strategy, in order to increase the water productivity in the present situation. Therefore, this research was carried out with 4 planting patterns and two Drip irrigation tape intervals (60 and 75 cm) in field scale (length 75 meters) and furrow irrigation treatment (control treatment) at Ekbatan station of Hamedan Agricultural and Natural Resources Research and Education Center in 2016-2017 and 2017-2018. The irrigation water requirements was calculated based on the average 10-year weather data of the Hamedan Airport Station using the Penman-Mantis formula. Irrigation intervals were considered as 6 and 12 days for drip and surface irrigation method respectively. The two-year average volume of water used in two irrigation systems, drip and furrow irrigation method was 4026 and 6028 (m3.ha-1), respectively. The Average of water productivity in drip irrigation treatments 1.73 kg.m-3 was calculated. The results showed that drip strip irrigation reduced 33 percent in water consumption and increased 73 percent in water productivity compared to furrow irrigation. Maximum and minimum two-year mean grain yield and water productivity were related to two T1 treatments (four rows of 15 cm spacing on both sides of the strip, with strips of 75 cm spacing) and furrow irrigation of 7443 and 5996 kg.ha-1 and 1.89 and 1 kg. m-3 respectively, which had a statistically significant difference p≤0.01. Therefore, According to critical water conditions in the country and if using drip irrigation (tape) in wheat crop, the distance between the strip of 75 cm and the four rows with a distance of 15 cm from each other around each strip that has the highest yield and water productivity, is recommended.

The precise estimation of reference crop evapotranspiration (ETo) has a significant role in improving water management in field and irrigation management. Different methods are available for ETo estimating. The FAO-PM equation is the most reliable method for ETo estimating, but this method requires large input data that is not fully measured in most meteorological stations. Also, the measured data lacks enough precision, especially in developing countries. Therefore, the researchers have used the empirical equations with minimum input data. In this study, the daily values of ETowere calculated at the synoptic station of Mashhad using Priestley-Taylor, Hargreaves, the FAO-PM proposed method by the lack of data and two forms of the Valiantzas equation. Then, the calculated values were compared with FAO Penman Monteith (PM) method. In this paper, new models for estimating ETo were presented by lack of wind speed and relative humidity data by modifying two forms of the Valiantzas equations. The results showed that by the lack of wind speed and relative humidity data, the modified Valiantzas model had the highest accuracy compared with the other methods. It was showed that the R2, RMSE and MAE indices were 0.85, 1 and 1.26 mm per day, respectively. Also, the results showed that the modified Hargreaves method had the highest accuracy when only temperature data is available.

A lysimetric study was conducted to determine the evapotranspiration (ETc) and crop coefficient (Kc) of wheat (Triticum aestivum L., cultivar Alvand) during growing season in Tabriz plain, northwest of Iran. The obtained values were compared to estimations made by FAO-56 Penman-Monteith equation. Wheat evapotranspiration was measured in ten days interval using a drained lysimeter. Results indicated that seasonal ETc of wheat is 732 mm, from which an average of 132 mm was supplied by precipitation and the remaining (i.e. 600 mm) by irrigation. Highest and lowest amount of ETc was observed in 2nd decade of June and 2nd decade of December, respectively. The average amount of measured ETc was in good agreement (R2=0.92, NRMSE=0.11) with the estimated value by FAO-56 approach (721 mm). Similarly, the mean measured grass reference evapotranspiration value for the entire wheat growing season was 715 mm, which was statistically consistent with the estimated value (743 mm) obtained by FAO Penman-Monteith method (R2=0.98, NRMSE=0.08). Kc for the initial stage, mid- and late season were 0.54, 1.22 and 0.39, respectively. The Kc values were also in close agreement with those estimated using modified empirical equation of FAO56-PM. in climatic condition of study region.

It is intended to optimize crop yields and economics of crop water use by irrigation. Implementing proper water use management by agricultural sector reduces water losses and increases distribution uniformity and crop yield. In order to improve water use management in agriculture, it is essential to determine crop water requirements of various crops with the required level of accuracy. The objective of this research was to determine garlic evapotranspiration, crop coefficients and water use efficiency in the Azarshahr region located in the eastern Azerbaijan province. The actual garlic evapotranspiration (ETa.o-s) was determined by the hydrological method, measuring the various components of water balance at the farm level including soil moisture at various soil depths and irrigation depths. The garlic actual seasonal evapotranspiration was 552 mm and its water use efficiency was 3.47 kg per cubic meter of evapotranspiration during the growing season. The garlic crop coefficients for the mid-season and late season stages were 1.37 and 0.57, respectively, when reference evapotranspiration was computed by the Penman-Monteith equation (FAO 56).