Vol. 22, No. 4 PRADHAN et al. 509 Journal of Agrometeorology 22 (4) : 509-517 (December 2020) Rainfall is crucial in agricultural planning for rainfed region which completely depends on rainfall and its distribution in any annual calendar. Variability in rainfall includes onset, distribution and cessation during the year which decides the agricultural operations. On other hands, quantum of rainfall might be same but its distribution varies according to rainfall events and crops undergo insufficient growth. The change in rainfall can’t be assessed easily due process of cloud formation and raining is unpredictable, but long-term rainfall analysis could be scaled up the planning of agriculture in rainfed region. Rainfall is the single most important factor in crop planning in rain-fed ecologies. Around 60% of the Indian agriculture is rain dependent, diverse, complex, under- invested, risky, distress prone and vulnerable; with diverse climate. India has a high spatial and temporal variability in rainfall and temperature (Rao et al ., 2010).Dry spells in rainfed agriculture are the general features in India. The perception of drought varies from one region to another depending upon normal climatic conditions, available water resources and agricultural practices (Pandey and Bhandari, Crop planning based on rainfall variability for Bastar region of Chhattisgarh, India ADIKANT PRADHAN 1* , T. CHANDRAKAR 1 , S.K. NAG 2 , A. DIXIT 3 and S.C. MUKHERJEE 2 1 AICRPDA, 2 S.G. CARS, IGKV, Jagdalpur, Chattisgarh 494 001, 3 ICAR-National Institute of Biotic Stress Management, Raipur, Chattisgarh 492 012, * Corresponding author:adi19agro@gmail.com ABSTRACT Analysis of long-term rainfall data (1986-2018) of Bastar region revealed decreasing trend in total quantum of annual rainfall with varying frequency and distribution. The quantity of winter and summer rains decreased drastically during 2008-18 as compared to earlier two decades (1986-96 and 1997- 2007). SW monsoon rain of 2008-18 was more than past two decades, whereas NE monsoon rain changed much in quantity except during 1997-2007. During 1986-96, the pre-monsoon shower was received in April, but later two decades the shower was received in May, which supports for summer ploughing and dry aerobic seeding. The cropping period almost synchronized between 22-43 standard meteorological week (SMW) reaching 93.11 mm per week as maximum rainfall. As the probability of 20 mm rainfall decreased from 75 to 50%, the crop yield got reduced by 30%. The mid-land rice with a probability of 13.47 to 16.07 mm rain per week supported growth phase during 17-21SMW. Whereas, upland rice maturing in 90-100 days could avoid dry spells, if the rice is managed by conservation furrows at the time of sowing. The summer ploughing is preferred with more than 40 mm rain in single day during March to April for mitigating dry spells. On the other hand, preparatory tillage and sowing were performed together in support of ripening niger and horsegram under probability of 75, 50 and 25% rain through crop planning. Maize and small millets reduced yield significantly when rainfall reached 75% deficit, whereas 25% deficit rain did not affect the yields. Key words: Rainfall, trend analysis, crop planning, seasonal rainfall, crop management and rainfed ecosystem. 2007). Intra-seasonal variability of rain has been further compounded due to increase in frequency and intensity of the rainfall and weather events under climate change scenario. Rainfall, being considered as the prime input for agriculture has its own erratic behaviour in terms of amount and distribution for better crop planning. Rainfall variability with time and space influences the agricultural productivity and sustainability of a region, as opined by Rockstrom and Falkenmark (2000). Rainfall analysis for crop planning was carried out in different regions of the country as reported by Agarwal (2000). The information on annual, decadal and seasonal rainfall of a region is useful for field preparation, seeding, irrigation, fertilizer application and overall in field crop planning. The pre-monsoon rains can be utilized for summer ploughing or seedbed preparation as well as raising rice seedlings in lowland during 20 to 22 nd (20-30, May) SMW (Rai and Singh, 2009). Climate change is very likely to have a major impact on hydrological cycle and consequently on available water resources, flood and drought frequencies, natural ecosystems, society and the economy (Ramos, 2001).