Investigating the impacts of latitude on virtual water content of major crops in the eastern provinces of Iran

Temperature is a key factor in yield, crop water requirement, and then virtual water of various agricultural products. Therefore, it is necessary to investigate the effect of latitude as one of the most effective factors on the variation of virtual water of agricultural products. In this research, the virtual water content of nine major plants including wheat, barley, alfalfa, sugar beet, corn, watermelon, tomato, onion and potato in four eastern provinces (including 56 cities) of Iran was calculated based on 20-year statistical data. Then, the average virtual water of each plant was calculated in different latitudes from 〖25〗^° to 〖38〗^°N at 1^° intervals using ArcGIS software. The regression between the average virtual water with crop water requirement and yield of the products revealed a positive correlation between virtual water and crop water requirement (r=0.65) and a negative correlation between virtual water and yield (r= 0.74). The average virtual water from the lowest to the highest was 0.19, 0.38, 0.45, 0.46, 0.53, 0.57, 1.59, 1.69, and 1.80 thousand cubic meters per ton for corn, sugar beet, onion, watermelon, tomato, potato, alfalfa, barley, and wheat, respectively. The results showed that the variation pattern of virtual water of the studied products across different latitude was Gaussian. Despite the different maximum values of virtual water, they occurred in the latitude range of 〖30〗^° to 〖33〗^° N and by moving away from the mentioned range to higher or lower latitude, the virtual water content of all products decreases.