An experiment was conducted in a commercial greenhouse to determine cucumber (Negin cultivar) evapotranspiration and CROP COEFFICIENT in two seasons of winter and spring cultivation in Hamedan province,Irrigation was done to meet 100% of the water requirement based on reaching the suction tensiometer to the field capacity (40 to 50 cm),The soil water balance was used to estimate plant evapotranspiration in the greenhouse,Stanghellini and FAO Penman-Monteith evapotranspiration methods were 214,2 and 181,5 mm in winter and 222,3 and 227,6 mm in spring,respectively,The evapotranspiration ratio by the FAO Penman-Monteith method inside and outside the greenhouse in winter and spring cultivation was 0,8 and 0,81,respectively,The actual evapotranspiration from soil water balance in winter and spring cultivation were 148,2 and 210,4 mm,respectively,The results showed that the average CROP COEFFICIENT in the initial,middle,and final stages of the growing season in winter planting was 0,69,1,43,and 1,05,and in spring planting were 0,63,1,15,and 0,9,respectively,The results of this study showed the necessary scientific basis for optimizing irrigation and saving water consumption,creating appropriate irrigation planning,and improving the CROP water use efficiency in the greenhouse,Also,by reducing excessive water consumption,it can reduce energy consumption and provide a maximum increase in product production efficiency and economic efficiency,The investigation of evapotranspiration,CROP canopy growth,and humidity changes during the growing season also showed that it is necessary to prevent the development of plant diseases,to use a higher ventilation level or forced ventilation in greenhouses,

The main purpose of irrigation is to achieve an optimum amount of yield with an economical use of water according to the CROP water requirement. An improved irrigation scheduling would lead to the reduction of the excess water use, and the enhancement of CROP production. In order to develop a proper irrigation scheduling, actual CROP water requirement must be determined.Accordingly, it was attempted to determine the water requirement of tuberose (Polianthes tuberose L.) irrigated by a drip irrigation system and grown in a glass greenhouse located in Varamin during 1392. In order to calculate the water requirement of the tuberose, a simple water balance method was applied.. Tensiometers were installed at two soil depths and were used to determine the time of irrigation events. Irrigation was applied at any time when the soil suction reached to 30 centibar. The Water requirement of Polianthes tuberose for a 144 day growing season (Jun. to Oct.) was found to be 350 mm. The average actual evapotranspiration of Polianthes tuberose was 2.5 mm/day. Based on the data collected from a Class A evaporation Pan located inside the greenhouse, the monthly CROP COEFFICIENTs for tuberose were between 0.5- 0.7.

In all methods in which the evapotranspiration of plants is counted as a reference, in order to generalize the results to the vegetation, it is necessary to multiply the acquired amount to the CROP COEFFICIENT. An experiment was done to estimate the CROP COEFFICIENT amount of evening primrose that was repeated four times in a time period of 70 days on March 2018. [D1], in a weather station located in the agriculture college of Ferdowsi University of Mashhad. In this experiment, the plants were cultivated in white plastic pots (micro-lysimeter) by 50 centimetre height and 30 centimeter width. The demanded amount of water to provide the plants' water needs is considered based on the field capacity. By controlling the water balance in pots, the evapotranspiration of plants was measure and by the use of evaporation pan A data, the CROP COEFFICIENT was calculated. According to the results of this study the CROP COEFFICIENT of evening primrose in the initial, middle and final steps are 0. 75, 1. 05 and 1. 00 respectfully. The average in whole the period evening primrose growth was 0. 92. The total amount of evapotranspiration of plants was estimated to be about 377 millimeters.

Optimal use of irrigation water requires to the precise irrigation planning and the accurate CROP COEFFICIENT estimation is the prerequisite of that particularly in the global scale. The aim of research was the comparison of preprocessing approaches of artificial neural network: regression and data reduction (principle component analysis and rotation) for CROP COEFFICIENT estimation using NDVI, RI, TVI, MSAVI, SAVI, mTVI, EVI, MNDVI and TVX for wheat CROP COEFFICIENT of East Azarbaijan Province. The performance of regression and data reduction approaches indicated the error criteria decreasing of data reduction approach, for example RMSE increasing from rotation to regression and from principle component analysis to regression was 11. 8 and 22. 7%, respectively. The used approaches of CROP COEFFICIENT estimation has overestimation as the average increase of CROP COEFFICIENT in the validation period showed 7. 7, 6. 13 and 4. 6% increasing of CROP COEFFICIENT from FAO to the regression, principle component and rotation approaches, respectively. Therefore, using the rotation in the data reduction analysis increased the accuracy of estimation. Decreasing of correlation COEFFICIENT-39. 13%-from MSAVI to NDVI indicated that the improved indices basis on the study area condition increased the performance of CROP COEFFICIENT estimation using satellite images.

A research was conducted in Fars province Agricultural Research Center in Zarghan area from 1999 to 2002 to determine the water requirement and CROP COEFFICIENT of wheat, applying Iysimeter. The results indicated that the water requirements of wheat were 720, 712 and 674 mm in the years of 1999-2000, 2000-2001 and 2001-2002, respectively. Using Penman-Monteith method for estimating reference CROP potential evapotranspiration, the CROP COEFFICIENTs for wheat at a four-stage CROP growth were 0.37, 0.64,1.10 and 0.51, respectively. Due to the inaccessibility of the whole weather data, we tried to figure out a solution to determine wheat water requirement to schedule irrigation planning for future. In this respect, we made use of a ten-day class A pan mean evaporation and CROP COEFFICIENT.

An important factor in determining water demand and optimum water management at different growth stages of sugar beet seed-bearing plants is CROP COEFFICIENT (Kc). The CROP COEFFICIENT (the ratio of sugar beet seed-bearing plant evapotranspiration (ETc) to grass evapotranspiration (ET0)) was calculated at different growth stages. The study was carried out by 6 lysimeters located in research station of Karaj Soil and Water Research Institute, Meshkinabad, Karaj in 2006. Two lysimeters where grass had been cultivated were used for determining ET0. To determine ETc of sugar beet seed-bearing plants, vernalized roots of sugar beet (200-250 g) were planted in four lysimeters. About 2000 and 1000 m2 were planted by the same CROP around the lysimeters of sugar beet seed-bearing plants and grass, respectively. The moisture contents of all lysimeters were measured during the growth period and also after harvest at the depth of 0-60 cm. To compensate soil moisture deficit, the irrigation was carried out after depletion of 40% of available moisture. In addition, precipitation, daily temperature, relative humidity, wind speed, sunny hours and evaporation from Class A pan was measured in a meteorological station located around the grass lysimeters during the growing period. The measured CROP factors included root number, total biomass weight, shoot dry weight, root dry weight, flowering stem weight, seed total weight, seed size, standard seed weight, 1000-seed weight, vigor, germination rate and seed viability. ET0 was calculated by evaporation pan and applying pan COEFFICIENT (Kp) of Karaj and also by Penman & Mantis method and was compared with the data of grass lysimeter. ETc, ET0 as well as Kc were estimated at different growth stages. The results showed that there was great conformity between two methods of ET0 calculation, i.e. by software CROPWAT and measurement. But at the beginning of the study, the ET0 calculated by grass lysimeters was lower than that calculated by meteorological data. However, over the time, the latter was affected by climatic parameters of temperature and sunny hours and increased with a stronger gradient than the former. This period was from the 50th day on. The results indicated that CROP evapotranspiration decreased at the initial stage because of undeveloped shoots and at final stage and at the end of growth period because of shoot yellowing and loss of green area and the need for the decrease in seed moisture during maturation. At the second stage, the CROP absorbed greater amount of water and as a result, its evapotranspiration increased because of the fast growth of sugar beet seed-bearing plants and the proliferation of aerial organs. At the third stage, since on one hand the leaf area of sugar beet seed-bearing plants was at its peak and on the other hand, the other organs were green, the evapotranspiration of the CROP was in its peak. At initial stages of the growth, ET0 was greater than ETc of sugar beet seed-bearing plants; however, the gradient of these two curves became almost constant over the time and ETc started to sharply decrease from the beginning of the final stage (i.e. about 90th day). The Kc of sugar beet seed-bearing plants at initial, development, middle and final stages was 0.29, 0.89, 1.12 and 0.66, respectively. Sugar beet seed-bearing plants consumed 35.13, 141.93, 273.59 and 65.49 mm water at initial, development, middle and final stages, respectively. Their peak water consumption was at middle stage with a rate of 7.82 mm/day.

Water is one of the most important factors that limit agricultural development, especially in arid and semiarid regions around the world. One of the important data for water management is the amount of water requirement of different plants. In this regard, by measuring water input and output in lysimeters and using water balance equation, CROP water use is determined. In this study, to determine CROP COEFFICIENTs of Milk thistle, as a valuable medicinal herb, a 1-year lysimetric experiment was conducted in Faculty of Agriculture, Birjand University, during the growing season of 2018. To conduct this project, six weighing lysimeters were used. To determine potential evapotranspiration as a reference CROP, grass was grown in three lysimeters and, in three other lysimeters, Milk thistle (Silybum marianum L. ) was planted. Based on the results, the reference CROP evapotranspiration and actual evapotranspiration of the plant were equal to, respectively, 1179. 5 and 920. 2 mm, during the growing period of 177 days. The length of different stages of plant growth, including the initial, development, middle, and end stages was 22, 35, 70, and 50 days, respectively. Finally, based on the FAO method, the CROP COEFFICIENT (KC) curve was drawn and the average of CROP COEFFICIENT at each of four stages of plant growth was determined as 0. 34, 0. 69, 0. 93, and 0. 77, respectively.

This research was conducted in Kooshkak Farm Research Station of Shiraz University in 1997 and 1998 in order to determine CROP COEFFICIENT and water requirements of rice, using lysimeter. The variety used was Champa-Kamfiroozi which is an early mature variety and is grown by most farmers in the area. Results showed that potential evapo-transpiration varied from 3.76 to 9.34 mm/day. Penman FAO method was used in calculating reference evapo-transpiration. CROP COEFFICIENT was 0.97 in the initial growth stage, 1.25 in the mid-season growth stage, and 1.09 at the time of harvest. Total CROP evapo-transpiration rates in 1996 and 1997 were 560 and 757 mm, respectively. Average deep percolation rates in the growing season was 3.4 and 3.5 mm/day in 1996 and 1997, respectively. Finally the total water requirements of rice in 1996 and 1997 were 1983 and 2361 mm, respectively.