Possible future climate for rice growing regions of India: Visualising 2050 and pest-related impact thereof.

Abstract

Changes in climatic variables may affect phenological phases of crops and affect plant growth and development, these changes also lead to emergence of new pests and diseases. Therefore, there is need to relate the trends of climatic parameters with rice productivity vis-á-vis the pest dynamics in the crop at different sites apart from projecting a future scenario for the crop in the country. For this long-term seasonal, monthly and weekly trends in climatic data, viz. temperature (maximum and minimum), relative humidity (morning and afternoon), rainfall and bright sunshine hours on seasonal (kharif or rainy season, rabi or post-rainy season and summer), monthly (January to December) and weekly (1-52 standard meteorological week or SMW) time scales for the period 1970–2010 at 14 different agroclimatic centers situated in rice growing regions of India were investigated. Mann–Kendall and Sen’s slope estimator, non-parametric test were used for studying the magnitute as well as statistical significance of trend in climatic data. Trend analyses of the climatic variables in rice growing regions of different locations (Palampur, Chiplima, Jagdalpur, Kaul, Cuttack, Kanpur, Hyderabad, Bengaluru, Samastipur, Pantnagar, Parbhani, Varanasi, Pune and Coimbatore) in India were studied. Positive trend for maximum temperature [for kharif season varied from 0.006°C/yr (Pune) to 0.045°C/yr (Chiplima)] were observed at five locations, negative trends [maximum for Jagdalpur (0.047°C/yr) and minimum for Bengaluru (0.011°C / yr)] were observed at eight locations while one location showed no change in maximum temperature. Minimum temperature showed increasing trend at most of the locations in kharif seasons. Relative humidity in the morning and afternoon also showed increasing trend at most of the locations in kharif. Increase in rainfall for kharif season varied from 8.990 mm/yr (Chiplima) to 0.008 mm/yr (Parbhani); the decrease was highest for Jagdalpur (5.329 mm/yr) followed by Coimbatore (4.485 mm/yr) and least for Varanasi (0.213 mm/yr). Positive and negative trends for total rainfall were observed at seven locations each. In kharif season (23-39 SMW), weekly maximum temperature showed a rising trend except at Cuttack, Kaul, Bengaluru, Pantnagar, Parbhani and Coimbatore while minimum temperature showed the increasing trend except at Palampur, Kanpur and Parbhani. Rainfall pattern showed a falling trend except at Cuttack, Hyderabad, Chiplima, Pune and Coimbatore. Monthly analysis of maximum temperature indicates that the trends are increasing in months of February, March, April, July, August and November while the trends are decreasing in months of January, May, June, September, October and December at most of the locations. Mimimum temperature showed an increasing trend in all months except January. Rainfall showed negative trends in monthly total rainfall during June-September. In June, seven locations showed negative trends which varied from 0.246 mm/yr (Kanpur) to 3.703 mm/yr (Jagdalpur); in July, 10 locations indicated negative trends that varied from 0.231 mm/yr (Samastipur) to 2.144 mm/yr (Chiplima); in August and September eight locations had negative trends. Coimbatore showed negative trends in monthly rainfall from May to December, the decrease was highest for November (4.854 mm/yr) and least in June (0.246 mm/yr). Based on these trends in climatic variables, monthly projected mean and seasonal change till 2050 were also obtained. The changes in climatic variable can be utilised for identification of the hotspot zones of important pest of rice based on the physiological aspect of pest. These changes may lead to possible rise in blast disease of rice at Kaul, Hyderabad and Pune. There looks a possible trend in reduction of the yellow stem borer insect-pest on rice crop in Central and Peninsular India with rise in the Northern latitudes of the country. There is need to relate the trends of climatic parameters with rice productivity vis-á-vis the pest dynamics in the crop at different sites apart from projecting a future scenario for the crop in the country. Key words: Climate variability, Mann–Kendall test,