Nitrogen availability and ammonia volatilization in biochar-based fertilizers

ABSTRACT

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.

KEYWORDS:

• Ammonia
• biochar-based fertilizer
• increased efficiency
• N loss
• slow release fertilizer

Acknowledgements

This study was supported by the São Paulo Research Foundation (FAPESP) under grant no. 2017/02886-7 and the Postdoctoral fellowship for the first author under grant no. 2015/21633-7.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Fundação de Amparo à Pesquisa do Estado de São Paulo [2015/21633-7, 2017/02886-7].