Phenology Analysis of Cotton and Maize in Lake Karla Watershed under the mild climate scenario (RCP 4.5)

In this paper, the effects of climate change on the phenology of cotton and maize are studied applying the Agricultural Policy/Environmental eXtender (APEX) simulation model. Cotton and maize are two dominant irrigated crops in Lake Karla Watershed (Central Greece). The phenology of maize and cotton is examined considering the mild climate scenario (RCP 4.5) with results from 5 climate models for the 2080 – 2100 period. The 5 climate models selected for this study are CNRM, HADLEY, ICHEC, IPSL and MPI. The scenario based on the HADLEY climate model predicts the highest values of average minimum and average maximum temperature while the ICHEC model predicts the lowest average minimum and average maximum temperature. In terms of precipitations, the MPI model predicts the lowest average precipitation while the  highest average precipitation is predicted by the CNRM climate model. The APEX model simulates plant development using the heat units approach and the heat units index (HUI), calculated as ratio between accumulated heat units and the total heat units needed to reach maturity, can be used as indicator of plant phenology. According to this approach, HUI = 1 indicates the physiological maturity. For all climate models the HUI shows that the cotton and maize reach maturity too early in the season as a result of which they also record lower yields, with the HADLEY climate scenario giving the lowest crop yield. According to the results provided by the APEX model for the two crops considered here, cotton will be affected the most by the predicted future climate.