Application of the Self-calibrated Palmer Drought Severity Index for Estimation of Drought Impact on Maize Grain Yield in Pannonian Part of Croatia

Ten-day self-calibrating Palmer Drought Severity Index (scPDSI) has been computed, based on observed 10-day mean air temperature, relative humidity and precipitation totals, as a parameter of drought impact on grain yield of 32 marketleading maize hybrids in 2017 and 2018 over 8 experimental locations in Pannonian part of Croatia. In addition, time series of the same climate variables for the closest “official” weather stations of Croatian Meteorological and Hydrological Service (DHMZ) for the period 1981-2018 have been used for scPDSI calibration and calculation. According to 10-day scPDSI, 2018 showed to be a „regular year“ while 2017 had a „moderate drought“ causing a maize grain yield reduction of 13%, compared to 2018. In spite some differences in climate aridity of central and eastern Croatia, a significant correlation between summer months’10-day scPDSI and maize grain yield has been determined. The highest average correlation coefficients across all maize hybrids for three summer months were determined for the last decade (10-day period) of July and consecutive three decades in August. The dependence of grain yield on scPDSI value is not the same for all hybrids indicating various tolerances of different hybrids to drought stress. The grain yield reduction was primarily affected by insufficient grain filling (smaller 1000-kernel weight) and to some extent by reduction of number of grains. For practical use, within the set of given 32 tested hybrids, the level of determined drought tolerance of a hybrid has to be considered along with its relative grain yield performance.