**Adam Kleofas Berbe´c \* and Mariusz Matyka**

Department of Systems and Economics of Crop Production, Institute of Soil Science and Plant Cultivation-State Research Institute, Czartoryskich 8, 24-100 Puławy, Poland; mmatyka@iung.pulawy.pl

**\*** Correspondence: aberbec@iung.pulawy.pl; Tel.: +48-81-4786-824

Received: 7 October 2020; Accepted: 25 November 2020; Published: 26 November 2020

**Abstract:** Agricultural land is mostly devoted to food production. Production of biomass is limited, as it competes for land with basic food production. To reduce land loss for growing food, biomass can be grown on marginal lands that are not usable for food production. The density of plantings have to be optimized to maximize yield potential. The presented study compares yield parameters end energy potential of six species of biomass plants (poplar, Siberian elm, black alder, white birch, boxelder maple, silver maple) cultivated in 18 planting densities from 3448 to 51,282 plants per hectare as short rotation coppice (SRC). Biomass yield parameters depended on both cultivated species and planting density. Green mass, dry mass, and shoot diameter was dropping with the increasing planting density for most tested species. Calculated yield of dry mass was dropping with increasing planting density for black alder, increasing for Siberian elm and boxelder maple. White birch and silver maple yields were optimal at moderate planting densities (25,000–30,000). White birch and boxelder maple had the highest average higher heating value (HHV). The optimal density of plantings should be chosen to best suit both the needs of cultivated species and to optimize the most important parameters of produced biomass.

**Keywords:** energy crops; planting density; calorific value; SRC
