Agricultural autumn drought and crop yield in 2011 in Poland

Over the recent years, drought has been occurring with an ever increasing frequency in Poland. The longer the rainless period lasts, the more acute its impacts are. Agricultural drought manifests itself as a prolonged period of water shortage for agricultural crops during their growth season resulting in yield reduction. Extent of drought was evaluated by the climatic water balance (CWB). Climatic water balance is an indicator that determines the state of humidification of the environment using data measured at meteorological stations. It is defined as the difference between atmospheric precipitation and evapotranspiration (in millimeters) calculated by an empirical formula taking into account: temperature, sunshine, and length of the day. CWB was calculated using meteorological data from 294 weather stations and weather posts across Poland. Spatial data from point measurements were interpolated using the Geographic Information System (GIS) software. Yield forecasts were made for major crops in Poland using agro-meteorological yield models and weather indices (WI). Yield figures were based on data from the Central Statistical Office of Poland (GUS). The autumn of 2011 was the driest in several dozen years in many localities of southeastern Poland. For instance, at the weather station in Pulawy, the lowest level of precipitation had been recorded since 1871. Weather conditions prevailing in the growing season of 2012 were very beneficial for winter cereals and winter rapeseed. As for sugar beet, the weather also favored high yields over most of the growing season, except the final stage of growth. Notwithstanding the extreme drought in the autumn of 2011, the good weather conditions in the remaining part of the growth period caused the yields of winter crops and sugar beet to be high. The very scant autumn precipitation, even though it had negative impact on the germination of cereals, seedling emergence, and seedling growth, did not cause any major losses to yields. Water supplies from September precipitation combined with frequent morning mists, fogs, and dew mitigated the impact of prolonged drought and were sufficient to sustain the yields at an acceptable level.