The current state of knowledge about the soil requirements of plants allows the identification of sensitive species (alfalfa, sugar beet, barley, wheat, peas, rape) and less sensitive (grasses, rye, oats, potatoes) to soil acidification (Fig. 6). The cultivation of specific plants in crop rotation therefore determines the date of soil liming on the one hand (the farmer should care to bring the soil pH to the optimal state in the year of cultivation of the plant most sensitive to acidification), and on the other – it allows to predict the results of all agrotechnical treatments, including fertilization.
Fig. 6 Regulation of soil pH in subs. Dołęga H., Zarzecka K. 2014 The degree of soil acidification directly affects the size of agricultural production, the quality of crops by shaping the functioning of the soil environment, and influences the chemical, biological and physical properties of the soil. Regulation of the soil reaction promotes the formation of a lumpy soil structure, which serves, inter alia, better aeration of the soil, increasing its porosity, improving water retention and circulation, and the accumulation of organic matter. In terms of fertilization, the pH of the soil influences the use of nutrients by plants, applied in fertilizers (Fig. 7).
Figure 7 Efficiency of nutrient use by plants on soils with different pH. Source: Hołubowicz-Kliza. 2012 The data presented in Figure 7 show that the efficiency of nitrogen, phosphorus and potassium use by plants increases with increasing soil pH. Regardless of the soil pH, the use of nitrogen and potassium by plants is usually greater than that of phosphorus. It should be noted that the utilization of N, P, K by plants cultivated in strongly acidic soils does not exceed 30% of the level achieved in the optimal pH conditions. Under acidic soil conditions (pH5-5.5), about 50-80% of nitrogen and potassium and 30-45% of phosphorus are used in production, in relation to the level of use of these components, with optimal soil pH. On the other hand, on slightly acidic soils, nitrogen utilization by plants reaches nearly 90%, and phosphorus – only less than 50% of that amount used by plants under optimal conditions for plant growth. Only the use of potassium by plants is similar on slightly acidic and neutral soils. It follows that even optimal fertilization with nitrogen, phosphorus and potassium will not bring the expected results under soil acidification conditions.
Figure 8 Influence of soil acidification on the rape root system (Photo by W. Szczepaniaka 2011) The effects of the above-discussed soil litter effect are shown in Figure 8. Acidification of the soil changes not only the biomass of the above-ground parts, but even the root biomass and plant habit to a greater extent. Underdevelopment and root dysfunction determine the insufficient supply of plants with water and nutrients. Disruption of the growth and functioning of the root system, the organ of water and mineral intake, causes a number of negative metabolic processes that determine the effective use of macronutrients, secondary components and micronutrients by plants (Matyka et al. 2014).
Figure 9 Influence of soil acidification on the biomass of above-ground and underground parts of cereal plants.