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 stresse s associated with observed intraseasonal and interannual variability in key climatic elements on the nature and extent of losses in growth and yield o f 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 crop ping season. The yields respond substantially to temporal variations in rai nfall (associated with observed swings in the continuity of monsoon). Prolo nged dry spells at critical life stages of the soybean crop are found to ad versely affect crop development and growth and hence the yields at selected sites. We have also examined the plausible effects of future climate chang e on soybean yields in the selected region based on simulations carried out for doubled atmospheric CO2 level and with modified weather variables usin g the available seasonal projections for the future. Our findings on the re sponse of elevated CO2 concentrations in the atmosphere suggest higher yiel ds (50% increase) for soybean crop for a doubling of CO2. However, a 3 degr ees C rise in surface air temperature almost cancels out the positive effec ts of elevated CO2 on the yield. Soybean crops at selected site are more vu lnerable to increases in maximum temperature than in minimum temperature. T he combined effect of doubled CO2 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 produc tivity even under the positive effects of elevated CO2 in the future. (C) 1 999 Elsevier Science B.V. All rights reserved.