Estimation of water requirement and plant coefficient of adaptive tree species for afforestation and green space in arid region (Case study: Robat Karim)

Water use planning for irrigation in arid and semi-arid regions is incredibly imperative. The objective of irrigation operations in these areas is to make favorable humidity conditions for plants. The current study probes the water requirement and plant coefficient of adaptive tree species treated for afforestation and urban green space in the arid region of Robat Karim town. To determine the water requirement of biennial species of Ash, Tehran pine, Tree of heaven, Berry, Black maple, and Black locust, in the period from 1 May to 20 November 2018 for 7 months, in Robat Karim city, soil moisture monitoring daily and on the definite hour was monitored by Soil Moisture Meter tool in the greenhouse. According to the results, among the six studied species, the highest rate of evapotranspiration was related to the Berry (146 mm) in the first decade of July, the Ash (142 mm) in the first decade of July, and the Black maple is in the first decade of July (128.2), respectively. The lowest evapotranspiration rates include the Tehran pine (10.1 mm), the Tree of heaven (11/24 mm), and the black locust (16 mm), respectively, all three belong to the third decade of November. Similarly, the variations trend in plant coefficients was minimal in the initial stage. In the two stages of growth and development and the middle stage, plant coefficient increased along with full foliation and development of stems and aerial parts. The highest plant coefficient for the studied species occurs on average in October, which is about the end of the middle stage. Then, in the final stage, with decreasing photosynthetic activity, aging, and leaf fall (November), the amount of plant coefficient decreases. The quantity of cumulative water requirement of the studied species also shows that the order of cumulative water requirement of the studied