Impact of climate change on paddy crop failure under different water regimes in Sri Lanka

This study highlighted the severity of paddy harvest failure under various water regimes by elaborating on spatiotemporal variations, and estimating the influence of climatic variation on such crop failure in Sri Lanka. A panel data set obtained from 18 districts from 1981 to 2019 was analysed. The Unharvest Index (UI) (i.e., an index that was developed to measure the intensity of crop failure) was estimated according to seasonal water regimes for each district. The panel data regression method was used for analysis. On average, 5 per cent of areas planted for paddy was unharvested annually, fluctuating with the coefficient of variation at 60 per cent with remarkable spatial variation. Harvest failure was more prominent in rainfed production as compared to irrigated cultivation; in dry and intermediate zones as opposed to wet zones; and in the Maha season (October to March) rather than the Yala season (April to September). Climate variability during the crop season significantly altered UI, especially during the early growth phase (Growth Phase I) as compared to the later growth phase (Growth Phase II). Temperature variability increased UI in rainfed production; an increase in the number of days above optimum temperature in Growth Phase I affected UI in minor irrigation; higher rainfall during Growth Phase I reduced UI in rainfed production; and higher rainfall variation reduced UI under all water regimes. Our findings suggest the importance of formulating localized climate-smart adaptation policies and specific crop insurance programs for rainfed paddy production.