Predicting isometropia- rainfall in dry wheat implantation and cultivation in Gonbad Kavoos province

Gonbad Kavoos province is considered as one of the poles of wheat production. This product is mainly planted in a dry way and before plantation the farmers wait for the first proper rainfall so that water supply could be provided for germination and the next steps. Therefore، to arrange a farming calendar، it is required to be aware of the probable dates of such rainfalls. Also during cultivation it is vital to know the no-raining days since it causes land humidity and pest. So، the purpose of this research is to provide a timetable to be used as a farming calendar by farmers for planting and cultivation. To prepare this table rainfall statistics more than 5 mm and less than 1 mm were obtained from related organizations to start planting and cultivation periods from 9 stations located in the area in 15 years. Then the date of rainy days during planting and cultivation was identified and turned into Julius day. The achieved numbers were practiced with different statistical distributions and the best one was selected. After that، the probable date of the considered raining was calculated in the first month of fall and the last month of spring. To estimate its accuracy 5 % of practiced days were randomly selected. The amount of rainfall was extracted from the stations located in the area. Also، synoptic information was taken from the site three days earlier from c. d. c. site and the maps of its various levels were drawn by Grads. Moreover، the source of systems، the cause of rain، the route and their humid sources and also the condition of rainfall factors were analyzed in the area. The results indicated that we could correctly estimate the time، amount، source and the route of raining systems in the beginning and at the end of planting season by the help of probability law and then arrange a farming calendar