The impact of climate variability and change on crop yield in Bulgaria

During the recent decade, the problem of climate variability and change, due to natural processes as well as factors of anthropogenetic origin, has come to the forefront, of scientific problems. The objective of this study was to investigate climate variability in Bulgaria during the 20th century and to determine the overall impact on agriculture. There was no significant change in the mean annual air temperature. In general, there was a decrease in total precipitation amount during the warm-half of the year, starting at the end of the 1970s. Statistical multiple regression models, describing the relationship between crop yield, precipitation, and air temperature were also developed. Several transient climate change scenarios, using global climate model (GCM) outputs, were created. The Decision Support System for Agrotechnology Transfer (DSSAT) Version 3.5 was used to assess the influence of projected climate change on grain yield of maize and winter wheat in Bulgaria. Under a current level of CO2 (330 ppm), the GCM scenarios projected a decrease in yield of winter wheat and especially maize, caused by a shorter crop growing season due to higher temperatures and a precipitation deficit. When the direct effects of CO2 were included in the study, all GCM scenarios resulted in an increase in winter wheat yield. Adaptation measures to mitigate the potential impact of climate change on maize crop production in Bulgaria included possible changes in sowing date and hybrid selection. (C) 2000 Elsevier Science B.V. All rights reserved.