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Rainfall is one of the important factors for crop planning under rainfed condition. Understanding of rainfall patterns of a region is of utmost importance for successful planning of crops in a profitable farming mode. The rainfall pattern decides the cultivation of crops, their varieties, adoption of cultural operations and harvesting of excess rainwater of any region (Kar, 2002). Generally cropping pattern is suggested considering the rainfall probability at different levels (Mahale and Dhane, 2003). Gupta et al. (1975) suggested that the rainfall at 80% probability could safely be taken as assured rainfall, while 50% probability is the medium limit for taking risk. Dhubri district is situated in the extreme western end of Assam. Monsoon usually starts from the month of June and continue up to early September. Paddy, wheat, other cereals, jute, mustard, pulses, vegetables etc. are the main crops of the district. As dependency of 70% population of the district is on agriculture and rainfall is deciding factor for success of rainfed agriculture, an attempt was made to understand the rainfall climatology by analyzing temporal and spatial rainfall distribution and its probability of occurrence of dry and wet spell and their distribution by analyzing rainfall data. Rainfall probability pattern has been studied by many scientists in India (Singh, et al., 2009; Ravindrababu et al., 2010).
For the present study, daily rainfall data recorded at the meteorological observatory of Rupsi airport, Dhubri (Latitude 26.8, Longitude 89.5 and altitude 131ft) for a period of 24 years were used. Markov chain method was used to analyse dry and wet spell of rainfall for the district. Rainfall of 20mm per week is adequate for all the growth stages of all the crops grown. Thus, if in a given week the rainfall received is less than 20mm that week is dry...