Assessment of a Single Application of Sewage Sludge on the Biomass Yield of Silphium Perfoliatum and Changes in Naturally Acid Soil Properties

In order to estimate the effect of granulated sewage sludge on the productivity of the cup plant (Silphium perfoliatum L.), soil physical and microbial properties, a field experiment was carried out in Western Lithuania, on a naturally acid moraine loam Bathygleyic Dystric Glossic Retisol with a pH of 4.3-4.9. The dry matter yield of the cup plant consistently increased over the experimental years from 2.83 t ha(-1) (in 2013) to 12.86 t ha(-1) (in 2016). Each year, the optimum sewage sludge rate for dry matter yield of cup plant was 45 t ha(-1). The use of both sewage sludge rates 45 and 90 t ha(-1) had a similar and positive impact on soil chemical composition, water-stable aggregate formation, topsoil bulk density, soil penetration resistance and moisture content. Each experimental year, the application of sewage sludge at a rate of 90 t ha(-1) had the strongest impact on the increase in soil microbial biomass carbon at the 0-30 cm depth. Experimental results suggest that when growing cup plant as an energy crop on a moraine loam Retisol, it is expedient to use granulated sewage sludge at a rate of 45 t ha(-1).