*Article* **The Effect of Mineral and Organic Fertilization on Common Osier (***Salix viminalis* **L.) Productivity and Qualitative Parameters of Naturally Acidic** *Retisol*

**Gintaras Šiaudinis 1,\*, Danute Karˇ ˙ causkiene˙ 1, Jurat ¯ e Aleinikovien ˙ e˙ 1,2, Regina Repšiene˙ <sup>1</sup> and Regina Skuodiene˙ <sup>1</sup>**


**Abstract:** One of the potential options for sewage sludge as an alternative organic material is the fertilization of energy crops. To evaluate the effect of granulated sewage sludge and mineral fertilization N60P60K60 on common osier's (*Salix viminalis* L.) biomass productivity and soil parameters, field trials were held in Western Lithuania's naturally acidic *Retisol* (WB 2014; pHKCl 4.35–4.58). After four years of cultivation and dependent on fertilization type, common osier dry matter (DM) yield varied from 49.60 to 77.92 t ha−1. Higher DM yield was related to an increased number of stems/plants. The application of a 90 t ha−<sup>1</sup> sewage sludge rate had a significant and positive impact on common osier productivity, as well as on the increment of soil organic carbon, total N, and mobile P2O5 content in the upper 0–30 cm soil layer. The use of both sewage sludge rates (45 and 90 t ha<sup>−</sup>1) had a similar impact on soil bulk density, water-stable aggregates, and the active soil microbial biomass. Annual mineral fertilization had little effect on the parameters studied. When growing common osier in *Retisol*, 45 t ha−<sup>1</sup> of a single sewage sludge rate was enough to maintain both plant and soil productivity.

**Keywords:** common osier; fertilization; dry matter yield; soil chemical parameters; soil bulk density; water-stable aggregates; soil microbial carbon
