Agroclimatic zonation for evaluating autumn sugar beet sowing feasibility in Khorasan Razavi and Khorasan-e-Jonobi Provinces

Autumn sugar beet sowing has priority to its spring sowing in terms of economic productivity and water use efficiency. In Khorasan Razavi and Khorasan-e-Jonobi provinces, sugar beet is only sown in spring. Therefore, it is necessary to evaluate the feasibility of autumn sugar beet sowing in these regions. Using geographical information systems is the best and inexpensive way to identify suitable areas for the crop sowing. Therefore, climatic information such as temperature and rainfall were collected. Then, cumulative thermal units, biomass productivity index, vernalization time, freez risk, rainfall occurrence and day length were estimated for each station. The computed values of climatic parameters were all converted to point data in ArcGIS environment. Results showed that in most of the Khorasan Razavi regions and central regions of Khorasan-e-Jonobi, there is a risk of bolting. In southwestern Khorasan-e-Jonobi, the total hours needed for sugar beet vernalization is less than the required time. However, less than 50 mm rainfall in this area is another limitation for sugar beet autumn sowing. Also, in areas with more than 190 mm rainfall, there is a risk of freezing, lack of optimal growing degree days (GDD), and vernalization. Based on final zoning map, 4.90% of the lands in these provinces were most favorable, 16.74% as favorable, 47.98% as medium, and 30.38% were not favorable for autumn sugar beet sowing.