Variability of drought occurrence during the maize (Zea mays L.) growing season in Central-Eastern Poland

Abstract

This study aimed to analyse the variability of precipitation deficits and excesses during the maize (Zea mays
L.) growing season in Central-Eastern Poland from 1971 to 2020. Meteorological data were obtained from IMGW-PIB
stations located in Siedlce, Włodawa, Legionowo, Pułtusk, Szepietowo, and Białowieża. The water balance was
calculated based on crop evapotranspiration (ETc), determined using a modified Hargreaves equation and crop
coefficients (kc). Results indicate that spring precipitation excesses predominated during the first two decades, whereas
from the 1990s onwards, water deficits became increasingly pronounced, particularly in June and July – critical months
for maize yield formation. At many stations, average deficits during this period exceeded 50 mm, with localised values
dropping below 75 mm. Principal component analysis (PCA) explained nearly 67% of total variance and revealed
a clear shift in hydroclimatic conditions. Early decades (1971–1990) were characterised by relatively stable conditions,
while the period after 1990 showed increasing variability, including more frequent alternation of deficit and excess
events. The most recent decades (2001–2020) were marked by strong intra-decadal variability and intensified
fluctuations in the water balance. Spatial differentiation was also noted: precipitation excesses were more frequent in
the north-eastern part of the region, whereas central locations were mainly affected by deficits. These trends are
consistent with broader climatic patterns in Central Europe, showing increasing drought frequency alongside more
intense precipitation events. The results highlight growing instability in water availability and confirm the need for
adaptive water management strategies, particularly during the most sensitive growth stages of maize.