Volume XXII |

Influence of climate conditions on maize yield in Oltenia (1990-2021)

Abstract: Maize, the most important cereal crop at global level, is a climate-sensitive plant. Consequently, the changes of the key meteorological parameters, namely temperature and precipitation amount, determine low yields, especially in rain-fed regions. The dependency of maize yield on climate conditions was assessed based on monthly values of the considered meteorological parameters (data from 14 meteorological stations for the period 1990-2021). The mean values of the analysed interval generally reveal proper conditions for the development of maize. However, starting with June until September, mean temperatures are 1 to 2°C above the optimum thermal threshold, as mentioned in the specialized literature. The growth degree days index (GDD) emphasizes Oltenia as a region with a very good thermal potential for maize, all mean values exceeding 1600°C, but the southwestern sector of the plain area has already exceeded 2000°C, underlining the increase in heat stress. The water deficit generates dry conditions, especially in Mehedinți, Dolj, and Olt, mainly in the interval July-August, which also corresponds to the maximum water requirements of maize. Drought prone areas were determined based on Selyaninov’s hydrothermal coefficient (HTC), which indicates slightly dry conditions in the growing season in the plain area, while northwards, in the piedmont and Subcarpathians, the climate is slightly humid, respectively moderately humid, drought risk decreasing gradually in this direction. At monthly level, August is the most problematic period as, except the northeastern part (Polovragi and Râmnicu Vâlcea), the entire region displays dry, moderately dry, and slightly dry conditions. The lowest maize yields correspond to the years 1993, 2000, 2002, 2007, and 2012. If in the first three years, the drastic yield reduction was mostly determined by a severe water deficit registered during the entire life cycle of the plant, in the last two years, the main restrictive factor was represented by temperature, mean monthly values exceeding 27°C and mean maximum values 35°C, especially in the plain area. Taking into account the projected increase in temperature and water deficit, the impact of climate conditions on maize crops may also be gradually higher in Oltenia and certain adaptation measures should be taken.