The effect of acidified slurry on crop uptake and leaching of nutrients from a loamy topsoil

Acidification is one of the recommended treatments to reduce NH3 emissions from animal slurry. Economically, the sulphuric acid is the most feasible agent to lower slurry pH. This study explains the impact of acidified slurry on soil and crop in a leaching trial. Pot experiments with ryegrass and cereal crops were used with 15 and 45 m3 ha−1 acidified slurry application. The effect of acidified slurry on ryegrass and maize yield was positive, increasing the yield by 40% and 20%, respectively, compared to unacidified slurry. There was a significant effect of acidified slurry on soil pH when large amount of acidified slurry (45 m3 ha−1) was used. Soil pH decreased by 0.1 units. The smaller amount of acidified slurry (15 m3 ha−1) had non-significant effect. Thus, for environmental protection purposes, it is necessary to ensure that the nutrient amounts applied with slurry, in particular easily soluble nitrogen and sulphur, correspond to the needs of the plants. Particular attention must be paid to Ca-poor soils. Sulphate ions are physically negatively absorbed in the soil, facilitating their availability in and leaching from the soil. With sulphate anions, an equivalent amount of Ca and Mg cations is always leached from the soil.