Application of Spruce Bark Biochar Minimizes Nitrogen and Carbon Leaching from an Eastern Newfoundland Podzolic Soil

Biochar has broad applications in agriculture, where its incorporation into soils is recognized as an effective strategy for improving soil quality, enhancing remediation, sequestering carbon, and mitigating climate change. Although the application of nitrogen fertilizers can enhance nitrogen leaching, integrating biochar may improve nutrient retention and reduce associated losses. However, the effects of biochar on nitrogen and carbon leaching in specific soil types remain unclear. This study investigated the impact of spruce bark biochar (SB550) on the leaching of total nitrogen (TN), nitrate (NO₃⁻), ammonium (NH₄⁺), and dissolved organic carbon (DOC) in agricultural soils of eastern Newfoundland. A greenhouse experiment was conducted with Festulolium forage grown in a soil–biochar mixture at five biochar rates (0, 2, 5, 8, and 10% v/v), with and without nitrogen fertilizer (0 and 60 kg N ha⁻¹). The results showed that SB550 biochar significantly reduced nutrient and carbon losses (p < 0.001). At the 10% biochar rate, leaching of NO₃⁻, NH₄⁺, TN, and DOC decreased by 48.6%, 80.4%, 60.0%, and 74.3%, respectively, compared with the control. These findings confirm that the addition of biochar is an effective amendment for minimizing nitrogen and DOC leaching, offering a promising strategy for sustainable nutrient management and environmental protection in this soil type.