10.18710/6TUE9U Hanssen, Kjersti Holt Kjersti Holt Hanssen https://orcid.org/0000-0002-1715-3092 Norwegian Institute of Bioeconomy Research DataverseNO 2026 Agricultural Sciences biochar forestry fertilization forest growth and yield Norwegian Institute of Bioeconomy Research (NIBIO) Norwegian Institute of Bioeconomy Research (NIBIO) Hanssen, Kjersti Holt Kjersti Holt Hanssen Norwegian Institute of Bioeconomy Research (NIBIO) 2026-05-19 2026-05-26 2020-05-01/2024-08-31 2015-10-01/2024-10-30 Survey data 10.18710/6TUE9U/RPGMKF 10.18710/6TUE9U/KZOXFB 10.18710/6TUE9U/76JHBW 3163 4435 19212 text/comma-separated-values text/plain text/comma-separated-values 1.0 Creative Commons CC0 1.0 Universal Public Domain Dedication. These datasets were used in our study of the effects of adding biochar and nitrogen-enriched biochar on the growth of two middle-aged pine forest sites in SE Norway. In replicated field experiments, we applied four treatments consisting of an unfertilized control, and addition of biochar (2.5 t ha-1), nitrogen fertilizer (150 kg N ha-1), or biochar loaded with nitrogen (2.5 t biochar + 150 kg N ha-1). Height and diameter of trees were measured before and five growing seasons after treatment, and increment cores were taken at the end of the study period. The dataset “Annual_rings_10years” contains data for annual rings from each tree five years before treatment (2015-2019) and five years after treatment (2020-2024). Units are 1/100 mm. The dataset “Plot_data” contains the plot wise data on average diameter (cm), height (m), trees per ha, basal area (BA, m2 ha-1) and standing volume (VOL, m3 ha-1) for autumn 2019 (before treatment) and autumn 2024 (five years after treatment). Norway, Akershus county, Norway, Innlandet county, 11.45 12.09 60.02 60.20 The Research Council of Norway 302158