Impact of Climate Change on Indian agroecosystems: Long-Term Trends from Site-Scale Data (1970–2020)

Climate change is expected to affect crop phenology and productivity. There are no long term studies on this topic in India primarily due to lack of observational data. We developed  a database of 5-decade long (1970-2020) site-scale observations of rice and wheat crop parameters by digitizing archived masters and doctoral thesis from agricultural universities in India. The observed Leaf Area Index (LAI) during the growing season shows that the major growing season for rice is June to October and for wheat it is November to April. Rice and wheat have a statistically significant increasing trend in yield (38 kg/ha/yr for rice and 34 kg/ha/yr for wheat) over the study period (p<.05). However, there is no considerable difference or trend observed in the growing season length of the crops during this period. Interestingly, a statistically significant increasing trend in harvest dates of wheat crop is observed from the dataset, harvest dates extended by ~14 days over the 50-year period (p<.1). Further, a case study was conducted on the rice crop, the largest crop by harvested area in India, to attribute the increasing trends in yield and other crop parameters to mean growing season temperature and increasing CO₂ levels. This case study comprised multiple site-scale data from two major agro-climatic zones: the Central India (CI) region and the Indo-Gangetic Plain (IGP) region during the wet season. The findings show increasing trends for plant height, grain yield, and straw yield in both the CI and IGP regions. In the IGP region, there is a negative correlation between mean temperature and crop variables, while a positive correlation is observed with CO₂ concentration. On the contrary, in the CI region, the mean temperature is positively correlated with plant height and straw yield but negatively correlated with grain yield. However, with increased CO₂ levels, all variables show a strong, significant positive correlation. These changes in crops may also be attributed to the development of hybrid crop varieties resulting from advancements in agricultural technology, which have impacted crop production and other plant variables. The growth of rice increased in elevated CO₂ levels but decreased under high temperature conditions. These changes in crop behavior underscore the need for adaptive strategies to mitigate the adverse effects of climate change on agriculture in India. This study is the first work that offers site-scale observational data for two major Indian agroecosystems and further investigates the two major agro-climatic zones. This data will be invaluable for future agricultural research and model development.