| Summary: | We evaluated the productivity and profitability of four highly productive poplars including <i>Populus deltoides × P. deltoides</i> (DD ‘140’ and ‘356’), <i>P. deltoides × P. maximowiczii</i> (DM ‘230’), and <i>P. trichocarpa × P. deltoides</i> (TD ‘185’) under two densities (2500 and 5000 trees ha<sup>−1</sup>), and three fertilization treatments (0, 113, 225 kg nitrogen ha<sup>−1</sup>) at three sandy coastal sites varying in soil quality. Green stem biomass (GSB) was estimated from the sixth-year stem diameter. Leaf-rust (<i>Melampsora castagne</i>) and beetle damage (by <i>Chrysomela scripta</i> Fabricius), the leaf area index (LAI) and foliar nitrogen, were measured in year two. At all sites, DD and DM had higher survival (>93%) than TD (62–83%). DD produced greater GSB (92.5–219.1 Mg ha<sup>−1</sup>) than DM (54–60.2 Mg ha<sup>−1</sup>) and TD (16.5–48.9 Mg ha<sup>−1</sup>), and this was greater under the higher density (85.9–148.6 Mg ha<sup>−1</sup> vs. 55.9–124.9 Mg ha<sup>−1</sup>). Fertilization significantly increased GSB on fertile soil but not marginal soils; a higher rate did not significantly enhance GSB. Leaf rust was higher for fertile soil (82%) than marginal soils (20–22%), and TD ‘185’ (51% vs. others 34%). <i>C. scripta</i> damage was higher for the higher density (+42%) than lower density, and TD ‘185’ (50% vs. others >38%). LAI was higher on fertile soil (1.85 m<sup>2</sup> m<sup>−2</sup>) than marginal soils (1.35–1.64 m<sup>2</sup> m<sup>−2</sup>), and under the lower density (1.67 m<sup>2</sup> m<sup>−2</sup> vs. 1.56 m<sup>2</sup> m<sup>−2</sup>). The high GSB producer DD ‘356’ had the lowest LAI (1.39 m<sup>2</sup> m<sup>−2</sup> vs. 1.80 m<sup>2</sup> m<sup>−2</sup>). Foliar nitrogen varied among genomic groups (DD ‘140’ 1.95%; TD ‘185’ 1.80%). Our plots were unprofitable at a 27 USD Mg<sup>−1</sup> delivered price; the biggest profitability barriers were the high costs of higher density establishment and weed control. The best-case treatment combinations of DD (‘140’, ‘356’) would be cost-effective if the price increased by 50% (USD 37.54 Mg<sup>−1</sup>) or rotations were 12 years (fertile-soil) and longer (marginal soils). The requirement for cost-effectiveness of poplars includes stringent and site-specific weed control which are more important than fertilizer applications.
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