Assessment of net water requirement index for different horticultural and field crops in Iran

Assessing the water requirements of horticultural and field crops is a prerequisite for optimizing water use with limited access to water and increasing crop productivity. The aim of this study was to determine the net water requirement (NWR) of 86 agricultural and horticultural crops (29 field crops and 57 horticultural crops) in Iran. The field measurements included the amount of irrigation water and crop evapotranspiration for at least one growing season in the production poles of each crop. These crops account for more than 85 percent of the cultivated area and irrigated production in Iran in different provinces. For all horticultural and field crops, the NWR was extracted from the water requirement system for three time periods of 10 years, 5 years and crop year 2022-2023. After examining the extracted data, the 10 years period was selected because the 10 years (2013-2023) showed more stable conditions. In this study, crops were divided into two groups: high– water- demand and low- water- demand crops and each group was divided into two categories: horticultural and field crops. The total NWR of all high- and low- water crops in the country is 54,444.51 mm, of which 72.42% of total irrigation water volume was used for high-water crops and 22.58% of the total irrigation water volume is used for low-water crops. The total NWR of high-water crops (horticulture and field crops) was 42148.42 mm, of which 70% was used for horticultural crops and 30% for field crops. The highest NWR index for high-water-demand horticultural crops were: papaya (1195.8mm), banana (1182.4 mm), chico (1191.1 mm), date (1108.4 mm) and guava (1090.7 mm) and the highest NWR index of water intensive field crops are sugarcane (1822.78mm), alfalfa (1457.17), potato (976.14), sugarbeet (926.79 mm) and tomato (803.1 mm), respectively. The results showed the genuine basis to eliminate crops with high water consumption and low economic returns such as papaya, sugarcane, alfalfa and spring sugar beet from the cropping patterns of arid and semi-arid regions and replace them with crops such as autumn sugarbeet and indigenous crops such as wheat and millet or annual crop rotations, thereby reducing both water consumption and imparting high economic benefits.