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SUMMARYThe objective of the present study was to compare the performance of seven different, widely applied crop models in predicting heat and drought stress effects. The study was part of a recent suite of model inter-comparisons initiated at European level and constitutes a component that has been lacking in the analysis of sources of uncertainties in crop models used to study the impacts of climate change. There was a specific focus on the sensitivity of models for winter wheat and maize to extreme weather conditions (heat and drought) during the short but critical period of 2 weeks after the start of flowering. Two locations in Austria, representing different agro-climatic zones and soil conditions, were included in the simulations over 2 years, 2003 and 2004, exhibiting contrasting weather conditions. In addition, soil management was modified at both sites by following either ploughing or minimum tillage. Since no comprehensive field experimental data sets were available, a relative comparison of simulated grain yields and soil moisture contents under defined weather scenarios with modified temperatures and precipitation was performed for a 2-week period after flowering. The results may help to reduce the uncertainty of simulated crop yields to extreme weather conditions through better understanding of the models’ behaviour. Although the crop models considered (DSSAT, EPIC, WOFOST, AQUACROP, FASSET, HERMES and CROPSYST) mostly showed similar trends in simulated grain yields for the different weather scenarios, it was obvious that heat and drought stress caused by changes in temperature and/or precipitation for a short period of 2 weeks resulted in different grain yields simulated by different models. The present study also revealed that the models responded differently to changes in soil tillage practices, which affected soil water storage capacity.

Pollutants affect not only the environment in which they originate since they are also transported by air currents to other locations. For this reason, air pollution is a global problem for all countries and the air and water quality need to be monitored carefully. More information on precipitation chemistry is required to determine the source of pollution as well as its effects on the ecosystems. In this study, precipitation chemistry has been analyzed for the first time by using simple bulk collectors located at four different sites in Northwest Turkey for a period of two years. About 650 sequential rainwater samples were collected and analyzed for pH, electrical conductivity, anions such as SO

Determination of Sensitivity of the Winter Wheat Crop to Meteorological Factors by DAISY Model    Nilcan Altınbaş1*, Mahir Aydın1, İrem Özmen1,  Barış Çaldağ1, Levent Şaylan1 1 Istanbul Technical University, Faculty of Aeronautics and Astronautics, Department of Meteorological Engineering, Istanbul, TURKEY [*]akatas@itu.edu.tr [*] Corresponding author: akatas@itu.edu.tr [*] ABSTRACT  Climate change or climate variability has always pose a risk for sustainable agricultural production.  Changes in meteorological factors may have different effects on different phenological stages of plants.  For this reason, not only the quantitative change of meteorological factors but also the temporal variation of these factors’ effects of plant growth and yield should be investigated. In this study, DAISY crop growth simulation model was used to analyze the sensitivity of winter wheat plant to meteorological factors during flowering period.  In this context, the effect of changes in temperature, rainfall and total solar radiation during the flowering period has been examined.  Key words:Climate change, Crop growth, Crop yield  [*] Corresponding author: akatas@itu.edu.tr

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