Crop Planning on the basis of Rainfall

The historical rainfall data for the period of 37 years (1981-2017) of Junagadh district in Gujarat were analyzed for selection of most appropriate probability distribution of rainfall.Gumbel max. distribution and Generalized extreme value distribution were found promising for most of the data sets. The best-fit distribution has been employed for obtaining the assured quantum of rainfall pertaining to 23-42 (SMW) at various probability levels. The minimum assured rainfall of 20 mm and more are expected from SMW 27 onwards at 70% probability. This indicated that the sowing of kharif crops has to be done during the 27 SMW for maximum utilization of rain water. Weekly rainfall was analyzed using Markov chain model and initial and conditional probabilities were estimated for 10 mm and 20 mm rainfall amount. The initial probability of getting 10 mm rainfall during 24th to 38th SMW is more than 50% except 25th and 26th SMW. Onset and withdrawal of monsoon in most of the year is observed in 23 SMW and 47 SMW respectively.Crop water requirement of groundnut (bunch and spreading), cotton and wheat are 338.63 mm, 414.08 mm, 818.42 mm and 581.28 mm respectively.