Effects of increased soil fertility and plant growth-promoting rhizobacteria inoculation on biomass yield, energy value, and physiological response of poplar in short-rotation coppices in a reclaimed tideland: A case study in the Saemangeum area of Korea

This study aims to investigate the physiological response, biomass yield and its bio-energy value to charcoal mineral fertilizer and Bacillus subtilis strain JS, a plant growth-promoting rhizobacteria, under nine different soil-enrichment procedures, and to provide a reference for suitable management strategies for short-rotation coppices on the marginal soils of reclaimed tidelands in Saemangeum area of Korea. The treatments used in this experiment were as follows: 1) 1:100 (volume basis) diluted rhizobacteria inoculation {B1, (B. subtilis: double-distilled water, v/v)}, 2) 1:50 diluted rhizobacteria inoculation (B2), 3) mineral fertilization {F1, (charcoal 200 kg ha⁻¹)}, 4) additional mineral fertilization {F2, (charcoal 300 kg ha⁻¹)}, 5) F1+B1, 6) F2+B1, 7) F1+B2, 8) F2+B2, and 9) control plot with no soil enrichment (C). The plant species used in this study is Populus euramericana. Net photosynthetic assimilation using leaves acclimated for 2 min at 1500 μmol m⁻² s⁻¹ was the highest in F1+B2, followed by B2+F2 and B2. Total biomass yield in F2+B2 was the highest by a significant margin among the nine soil-enrichment procedures, whereas that in the control soil was lowest. Plants in all soil conditions provided similar net calorific values of dry mass, and they all fell within the third grade of wood pellet quality criteria of the National Institute of Forest Science standard specification (Korea), within the premium category in the Pellet Fuels Institute standard specification (US), and within the A1 category in the EN-Plus standard specification (EU). Moreover, it was confirmed that the poplar was suited to produce wood pellets for heating energy.