2024, Vol. 7, Special Issue 1

author(s)
Pazhanivelan Sellaperumal, Ragunath Kaliaperumal, Kumaraperumal Ramalingam, S Satheesh and NS Sudarmanian

abstract
Climate change has emerged as a critical issue in recent decades, significantly impacting agricultural production and productivity. Despite some debate about its existence, numerous scientific studies have focused on quantifying climate change effects, particularly shifts in rainfall and temperature patterns, and their influence on crop growth. Indicators such as rainfall distribution, temperature deviations, and cropping pattern changes from historical norms have been widely used in these assessments. The Length of Growing Period (LGP) defined as the number of days available for crop production based on rainfall and Potential Evapo-Transpiration (PET) serves as a useful metric for evaluating climate change impacts, especially in rainfed agriculture. Data derived from open-source satellite products like MODIS, TRMM, and GLDAS were used to compute LGP deviations, season onset, and classification of growing periods. Findings revealed a marked decline in LGP across Tamil Nadu from 2001 to 2017. In 2001, over 76% of the area fell under the 100-150 day LGP category, which dropped to just 35% by 2017. Annual classification into single and double cropping seasons showed a significant presence of double-season areas from 2001 to 2010. However, the emergence of ‘No prominent season’ zones became evident from 2011 onwards. While some regions saw no significant shift in season onset, other areas experienced a forward shift of more than two weeks, especially in eastern parts. Conversely, parts of northwestern Tamil Nadu experienced a backward shift exceeding two weeks. The period from 2001 to 2010 showed a general increase in LGP, followed by a decline in later years. These changes highlight the growing unpredictability of rainfed agriculture and underscore the urgent need to reorient crop calendars and growing periods in affected areas to mitigate yield losses and adapt to changing climatic conditions.