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Increasing N use efficiency is an important strategy to intensify sustainable agriculture, optimize nutrient use, and reduce N loss to the environment via different routes. Owing to its physicochemical properties, biochar can be used as an additive to produce biochar-based fertilizers (BFs) with increased efficiency. We investigated N availability and ammonia loss from 17 BFs (3%–38% N). N availability and release from BFs were evaluated by water extraction experiments and soil column leaching. BFs (5%–10% N) had an average of 64% solubilized N after five extractions, whereas urea had 98% solubilized N. However, BFs produced with urea released N more slowly in soil, with the release rate 60% less than that of urea. Ammonia volatilization was evaluated using a 22-d experiment, where N was applied to soil surface (pH = 4.4). We compared urea, BF granulated with urea, and BF produced by coating urea granules with acidified or unacidified biochar. Compared to urea, biochar-based fertilizers granulated with urea and urea granules coated with acidified biochar significantly reduced (t-test at 5%) ammonia volatilization by 14%. The results demonstrated the potential of BFs as enhanced efficiency fertilizers. Therefore, BFs might be a good option to mitigate N loss. [ABSTRACT FROM AUTHOR]

• BC-based fertilizers with 51% of BC had 21% higher maize yield than urea. • Grain N was 16% higher with BC-based fertilizers than with mineral sources. • BC-based fertilizers replacing urea result in more favorable carbon balances. • BN 51/10 use promoted soil C sequestration and helped mitigate net greenhouse gases. The sustainable development of agriculture depends on increasing N use efficiency (NUE) and consequently reducing N losses from different sources, such as NH 3 volatilization, NO 3 − leaching, and N 2 O emissions. While the chemical and physical properties of biochar (BC) in fertilizers have been evaluated to increase NUE, a lack of information exists regarding the effects of BC amendments in tropical soils. We performed a one-year field experiment with tropical soil to evaluate the effects of BC-based N fertilizers (BN) on maize yield and on greenhouse gas (GHG) emissions. The treatments consisted of five fertilizers: ammonium nitrate (AN), urea (U), BN 51/10 (51% BC, 10% N), BN 40/17 (40% BC, 17% N), BN 29/20 (29% BC, 20% N), and a control (without N fertilizer). The N fertilizers (80 kg N ha−1) were broadcast 20 days after sowing. Yield, grain N uptake, NUE, ammonia volatilization, and GHG emissions were measured. The results demonstrated the potential of BNs to enhance the efficiency of the fertilizers. BN 51/10 and BN 40/17 had an average maize yield that was 26% higher than that of U, and BN 51/10 resulted in a NUE that was 12% higher than what was observed for U. Both the effects on yield and NUE were attributed to lower N release rates of the BN-amended fertilizers compared to that of the conventional soluble N sources. The BC-based fertilizers presented better environmental performance, and BN 51/10 showed the lowest emission intensity when C sequestration by BC was not considered, with a value that was 14% lower than that of the U treatment. When considering C sequestration by BC, the emission intensity of the C equivalents demonstrated that all BNs presented C sequestration that differed from that of the mineral N sources. BC-based nitrogen fertilizers may have promising applications for sustainable agricultural development by mitigating N losses and increasing C stocks. [ABSTRACT FROM AUTHOR]