Document Type : Original Article

Authors

• Amir Eslami ¹
• Mohammad Mehdi Nakhjavanimoghaddam ²
• Mohammadmehdi Gasemi ²
• Akbar Jokar ¹

¹ Assistant Professor, Agricultural Engineering Research Department, Fars Agricultural and Natural Resources Research and Education Center, Agricultural Research Education And Extention Organization, Shiraz, Iran

² Assistant Professor of Irrigation and Drainage Engineering Department, Agricultural Engineering Research Institute (AERI), Agricultural Research, Education and Extension Organization (AREEO), Karaj, Iran

Abstract

Extended Abstract
Introduction
Recognizing and removing production obstacles such as climate changes and drought and water shortage challenges, on one hand, and performance instability and Inappropriate product quality, on the other hand, has doubled the importance of paying attention to applied research and transfer of technical knowledge to the field of production. Therefore, the present research was conducted with the aim of investigating the impact of farmers' management in different climates of cotton-producing areas of Fars province on the irrigation water productivity index.
Methodology
This research was carried out in the field in order to determine the cotton irrigation water in the fields under the management of farmers during one cropping season (2018-2019) in Larestan, Darab and Fasa areas in Fars province. A total of 20 experimental farms were selected. Registration of irrigation program and measurement of water source flow using WSC flume device and volumetric meter were also done. After determining the flow rate of the water source, according to the number of hours of irrigation, the applied irrigation water in each irrigation turn was determined in each of the selected fields. The simplest method that can be used in farmers' fields to estimate the physical productivity of irrigation water of a plant is to measure the yield and amount of irrigation water during the cropping season. In order to estimate the pure water requirement of cotton in the study areas, first, the reference evapotranspiration was calculated using the ETo-calculator software (Raes, 2012) according to the FAO Penman-Monteith method. The meteorological information used included daily average maximum and minimum air temperature, maximum and minimum relative humidity, wind speed at a height of 10 meters (m/s) and the number of sunny hours per day in a statistical period of 10 years. In order to determine plant coefficient values in different stages of cotton growth, first, according to field observations, the four stages of cotton growth were determined. Then the plant coefficients related to each growth stage were selected based on the proposal of FAO publication 56 (Allen et al., 1998). Considering the efficiency of 60 and 90% for surface and drip irrigation systems, respectively (Abassi et al., 2015), the gross water requirement of farms was obtained.
Results and Discussion
The average yield of cotton in Larestan, Darab and Fasa cities is 4300, 5775 and 3080 kg per hectare, respectively. As it is known, the lowest crop yield was obtained in Fasa district, which could be due to high soil salinity. According to the research of Nakhjavani Moghadam et al. (Nakhjavani Moghadam et al., 2019), the average yield of cotton in the country is reported to be 3383.5 kg per hectare, which has increased by 27 and 70 percent in Larestan and Darab, respectively, and the cotton average yield in Fasa is 9 The percentage has decreased. The average amount of irrigation water in selected farms and 18 farms that were irrigated by surface irrigation method was 9944 and 9899 cubic meters per hectare, respectively. The average water productivity in the selected farms of the province was 0.5 kg/m³, which is 16.3% higher than the national average reported by Nakhjavani Moghadam et al. Also, the average water productivity in the surface irrigation method was 0.49 kg/m³. The average water requirement of cotton in the selected farms of Fars province was calculated as 849, 888 and 989 mm, respectively, based on 10-year meteorological data, meteorological data of the project implementation year and the national water document. Surface and drip irrigation methods in Darab city did not have significant statistical differences in any of the indicators.
Conclusions
Taking into account the latest statistics on the area under cotton cultivation in Fars province (19,269 hectares), the volume of water consumed in all the cotton fields of the province is estimated at 191 million cubic meters per year. The results showed that the average indicators of yield, irrigation water and productivity of cotton irrigation water in 18 selected farms of the province that were irrigated by surface method were 4450 kg/ha, 9899 m³/ha and 0.5 kg/m³, respectively. Based on the results of this research, it is recommended that the optimal planting and harvesting dates are observed by the operators on June 20 and November 1, respectively. On the other hand, by accepting the amount of regulated deficit irrigation (20-25%) during the growth period, the optimal irrigation water amount regardless of the leaching coefficient for the cotton plant in these areas with the surface irrigation method should be considered between 9000 and 10000 cubic meters per hectare. It is also emphasized that before planting, farmers should take the soil sample and test it and perform optimal fertilization management according to the recommendations of experts.

Keywords

• Cotton yield
• Irrigation water
• Irrigation management
• Water requirement

Main Subjects

• Water Resources and Consumption