Fertilizers replenish stocks of nutrients in the soil in an accessible form and supply them with plants. At the same time, they have a great influence on the properties of the soil and thereby affect the yield also indirectly. Increasing the yield of plants and the mass of roots, fertilizers enhance the positive effect of plants on the soil, contribute to the increase in its humus, improve its chemical, water-air and biological properties. Organic fertilizers (manure, composts, green manure) have a great direct positive effect on all these soil properties.
Acid mineral fertilizers, if they are systematically applied without organic fertilizers (and on acidic soils without lime), can have a negative effect on the properties of the soil (Table 123). Prolonged use of them on acidic, unrecognized soils leads to a decrease in soil saturation with bases, increases the content of toxic aluminum compounds and toxic microorganisms, degrades the water-physical properties of the soil, increases the bulk weight (density), reduces soil porosity, aeration and water permeability. As a result of the deterioration of the soil properties, the yield increase from fertilizers is reduced, the “negative effect” of acid fertilizers on the crop is manifested.