Agronomy 2013, 3(2), 275-293; doi:10.3390/agronomy3020275
A Review of Biochar and Soil Nitrogen Dynamics
1 Department of Soil and Physical Sciences, Faculty of Agriculture and Life Sciences, Lincoln University, Lincoln 7647, New Zealand2 Bio-Protection Research Centre, PO Box 84, Lincoln University, Lincoln 7647, Christchurch, New Zealand3 Department of Plant Ecology, Heinrich-Buff-Ring 26-32 (IFZ), University Gießen, Germany4 School of Biology and Environmental Science, University College Dublin, Belfield, Dublin 4, Ireland
* Author to whom correspondence should be addressed.
Received: 1 February 2013; in revised form: 8 April 2013 / Accepted: 8 April 2013 / Published: 16 April 2013
(This article belongs to the Special Issue Biochar as Option for Sustainable Resource Management)
Abstract: Interest in biochar stems from its potential agronomic benefits and carbon sequestration ability. Biochar application alters soil nitrogen (N) dynamics. This review establishes emerging trends and gaps in biochar-N research. Biochar adsorption of NO3−, up to 0.6 mg g−1 biochar, occurs at pyrolysis temperatures >600 °C with amounts adsorbed dependent on feedstock and NO3− concentration. Biochar NH4+ adsorption depends on feedstock, but no pyrolysis temperature trend is apparent. Long-term practical effectiveness of inorganic-N adsorption, as a NO3− leaching mitigation option, requires further study. Biochar adsorption of ammonia (NH3) decreases NH3 and NO3− losses during composting and after manure applications, and offers a mechanism for developing slow release fertilisers. Reductions in NH3 loss vary with N source and biochar characteristics. Manure derived biochars have a role as N fertilizers. Increasing pyrolysis temperatures, during biochar manufacture from manures and biosolids, results in biochars with decreasing hydrolysable organic N and increasing aromatic and heterocyclic structures. The short- and long-term implications of biochar on N immobilisation and mineralization are specific to individual soil-biochar combinations and further systematic studies are required to predict agronomic and N cycling responses. Most nitrous oxide (N2O) studies measuring nitrous oxide (N2O) were short-term in nature and found emission reductions, but long-term studies are lacking, as is mechanistic understanding of reductions. Stable N isotopes have a role in elucidating biochar-N-soil dynamics. There remains a dearth of information regarding effects of biochar and soil biota on N cycling. Biochar has potential within agroecosystems to be an N input, and a mitigation agent for environmentally detrimental N losses. Future research needs to systematically understand biochar-N interactions over the long term.
Keywords: biochar; immobilization; mineralization; nitrate leaching; nitrogen; nitrous oxide; ammonia volatilisation
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