Conversion and acidifying effect of elemental sulphur in an alkaline loess soil

Abstract

Since approximately half of the soils in the loess region of central and southern Saxony-Anhalt are alkaline, it should be studied whether pH can be reduced by fertilization with elemental sulphur. Pot experiments with oats (fertilization equivalent to 0, 80, 200 and 500 kg S0 ha−1) and without plants (1 – 60 S0 t ha−1) were carried out. In soil, sulphur was rapidly converted into sulphuric acid independently of the vegetation. However, a pH reduction from pH 7.4 to 7.1 and 6.9 respectively within 16 weeks was only achieved with fertilization rates of 4 – 6 t S0 ha−1. Quantities of 10 t and more led to substantial soil acidification. The buffering by carbonate dissolution ran slower than the sulphuric acid formation (reduction from 4.0 to 3.5% CaCO3 with 6 t S0 ha−1 after 76 weeks). Hence, a re-increase of soil pH is possible. Fertilization rates of up to 500 kg S0 ha−1 did not impair plant growth in soil with high mineral S content.