STUDYING THE IMPACT OF EARLY AUTUMN AND LATE SPRING FROSTS ON AGRICULTURAL CROPS YIELD IN IRAN

Abstract

To study early autumn and late spring frosts and its relation to the yield of agriculture crops in Semnan province we used statistics the least daily minimum temperature of 6 stations in the months of October and November and April during the period (1993-2014) as well as information on yield of agricultural crops from horticulture department of agriculture Organization. Using Pearson correlation coefficient between yield and frequency of early autumn and late spring frosts were studied and finally induced to study the frosts trends for each station. Early frosts of autumn in the province date from 20 October to 23 November and latest frosts ranged from 3 to 23 April and Biarjomand station experience earliest autumn and latest spring frosts. The Relationship between crop yields with frost Occurrence frequency shows that by increasing the number of days of early autumn frosts reduced wheat yield. This condition is for crops such as peas, walnuts and grapes, too. Amongst, the greatest impact is on the potato crop, which is closely related to the pattern of cultivation and harvest. On the other hand, it was found that late spring frosts in the province have the greatest impact on horticultural crops such as cherries, peaches, walnuts and grapes. As a result, early and late frosts changes in Semnan and Miami has increased, which in coming years will be also affected by this situation. Also, early frosts of autumn at harvest time and late spring frosts during flowering have many effects on crop yield.