Growth and yield responses of soybean in Madhya Pradesh, India to climate variability and change

This study is aimed at assessing the impact of thermal and moisture stresses associated with observed intraseasonal and interannual variability in key climatic elements on the nature and extent of losses in growth and yield of soybean crop in central India through the use of CROPGRO model. The crops are found to be more sensitive to higher cumulative heat units during cropping season. The yields respond substantially to temporal variations in rainfall (associated with observed swings in the continuity of monsoon). Prolonged dry spells at critical life stages of the soybean crop are found to adversely affect crop development and growth and hence the yields at selected sites. We have also examined the plausible effects of future climate change on soybean yields in the selected region based on simulations carried out for doubled atmospheric CO(2) level and with modified weather variables using the available seasonal projections for the future. Our findings on the response of elevated CO(2) concentrations in the atmosphere suggest higher yields (50% increase) for soybean crop for a doubling of CO(2). However, a 3 degrees C rise in surface air temperature almost cancels out the positive effects of elevated CO(2) on the yield. Soybean crops at selected site are more vulnerable to increases in maximum temperature than in minimum temperature. The combined effect of doubled CO(2) and anticipated thermal stress (likely by middle of the next century) on soybean crop is about 36% increase in yield at the selected sites. A decline in daily rainfall amount by 10% restricts this yield gain to about 32%. Deficient rainfall with uneven distribution during the monsoon season could be a critical factor for the soybean productivity even under the positive effects of elevated CO(2) in the future. (C) 1999 Elsevier Science B.V. All rights reserved.