Effect of biochar on soil fertility, nitrate losses, dissolved organic carbon, forage crop production and greenhouse gas (GHG) emissions

The growing need to improve soil fertility and enhance crop production has led to increase in the nitrogenous (N) fertilizer use, which could result in detrimental effects due to the possible increase in greenhouse gas (GHG) emissions and nitrate leaching losses. Therefore, there is a pressing need to address the negative environmental effects of nitrogen fertilizer use through better management practices. Biochar applications to the agricultural soils have been recognized as a unique strategy for improving soil fertility, mitigating GHG emission, enhancing carbon sequestration, and plant nutrient use efficiencies by increasing nutrients uptake while reducing the leachate losses. Considering multidimensional benefits of biochar, the current study investigated the effects of different biochar application rates on podzolic soil fertility, GHGs mitigation potential, soil nitrogen dynamics, crop productivity and forage quality in eastern Newfoundland podzolic soils. The first experiment was conducted to assess the nitrate adsorption potential of four different biochar feedstocks including, spruce-bark biochar at 550⁰C (SB550), hardwood biochar at 500⁰C (HW500), fir/spruce biochar at 427⁰C (FS427), and softwood biochar at 500⁰C (SW500). The results showed that SB550 has the highest nitrate adsorption capacity (184 mg g⁻¹) among others. The second experiment was conducted in a greenhouse with five rates of SB550 and two N application levels to (i) investigate the capability of biochar application for improving the soil fertility, forage production, forage quality, and nutrient uptake, (ii) assess their effects on soil total nitrogen (TN), nitrate (NO₃⁻), ammonium (NH₄⁺) dynamics and dissolved organic carbon (DOC). Results indicated that biochar application significantly improved soil pH, Soil Organic Matter (SOM), Cation Exchange Capacity (CEC), and available nutrients in the soil. Moreover, SB550 biochar has significantly reduced NO₃⁻, NH₄⁺, TN, and DOC in the leachate compared to the control treatment. The third experiment was conducted under field conditions. Four rates of HW500 biochar applications, with three levels of nitrogen fertilizer applications (Urea 46-0-0) that were applied at the rates of 0, 65 and 130 N kg/ha to the Festulolium forage crop field. Biochar application has significantly reduced GHG emissions and increased the Festulolium productions. Thus, biochar application has shown to be a promising technique for sustainable agricultural management practices in the eastern Newfoundland Podzolic soil