Most of Poland’s soils were made of glacial rocks of glacial origin – sands and till clay. This type of rock is poor in calcium carbonate (CaCO3). Calcium carbonate is the primary chemical in soil responsible for neutralizing soil acids. Additionally, Poland lies in the temperate climate zone. Every year, a similar amount of water reaches the surface of the soil to that which undergoes evapotranspiration (evaporation from the surface of soil and plants).
Nevertheless, in a temperate climate, cyclical changes in weather conditions in the form of successive seasons are typical. Most precipitation occurs in the summer, but at this time high temperatures intensify evaporation. Therefore, in the summer there is often a shortage of water in the soil. The situation is usually different from autumn to spring. Although in autumn, winter and spring there is less rain than in summer, low temperatures and low evapotranspiration cause excess water in the soil.
Water, especially on light, sandy soils, moves through the thick pores into the soil profile. This water dissolves the reaction products of carbonate and soil acids – bicarbonates. These two fundamental phenomena are the reason why our soils are constantly acidified naturally. If we take into account the fact of human activity (application of acidifying mineral fertilizers, etc.), the acidification of soils is influenced by anthropogenic factors, significantly lowering their pH. Data for the period 2015-2018 confirm that 56.8% of our soils are acidified. The share of strongly acidic soils is 13.9%, and acidic – 42.9%. Most strongly acidic and acidic soils are found in the following voivodeships: Podlaskie, Łódzkie and Mazowieckie, and the lowest in Kujawsko-Pomorskie – 18%.
Badora, Kozłowska-Strawska, 2011, found that under soil acidification conditions, plants are exposed to aluminum stress. This reduces the yield. Aluminum is toxic to the root system of plants, impairing its functions (water and nutrient uptake). The symptoms of aluminum toxicity are therefore closely related to the symptoms of phosphorus, calcium and magnesium deficiency.