Biochar, soil and land-use interactions that reduce nitrate leaching and N2O emissions: A meta-analysis

Authors: BORCHARD, NILS - Bogor Agricultural University; SCHIRRMANN, MICHAEL - Helsinki University; CAYUELA, MARIA - Universidad De Murcia; KAMMANN, CLAUDIA - Hochschule Geisenheim University; WRANGE-MONNIG, NICOLE - University Of Rostock; ESTAVILLO, JOSE - University Of Basque Country; FUERTES-MENDIZABAL, TERESA - University Of Basque Country; Sigua, Gilbert; Spokas, Kurt; IPPOLITO, JAMES - Colorado State University; Novak, Jeffrey

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/4/2018
Publication Date: 10/19/2018
Citation: Borchard, N., Schirrmann, M., Cayuela, M.L., Kammann, C., Wrange-Monnig, N., Estavillo, J., Fuertes-Mendizabal, T., Sigua, G.C., Spokas, K.A., Ippolito, J., Novak, J.M. 2018. Biochar, soil and land-use interactions that reduce nitrate leaching and N2O emissions: A meta-analysis. Science of the Total Environment. 651:2354-2364. https://doi.org/10.1016/j.scitotenc.2018.10.060.
DOI: https://doi.org/10.1016/j.scitotenv.2018.10.060

Interpretive Summary: Agriculture accounts for about 60 percent (%) of global anthropogenic nitrous oxide (N2O) emissions, largely due to organic and mineral nitrogen (N) fertilizer use and the extended use of legumes either as crops (soy, pea, bean or groundnut) or as green cover. Biochar can reduce both N2O emissions and nitrate (NO3)-leaching. However, refining biochar’s use for estimating these types of losses remains elusive. For example, biochar properties such as ash content and labile organic compounds may induce transient effects that alter N-based losses. Thus, the aim of this meta-analysis was to assess interactions between biochar-induced effects on N2O emissions and NO3- retention, regarding duration of experiment as well as soil and land use properties. Data were compiled from 88 peer-reviewed publications resulting in 701 observations up to May 2016 and corresponding response ratios used to perform a random effects meta-analysis, testing biochar's impact on cumulative N2O emissions, soil NO3- concentrations and leaching. This meta-analysis revealed that biochar stimulates an overall N2O emissions reduction of 38% with greater reductions immediately after application. The time dependent impact of biochar application on soil N2O emissions is a crucial factor requiring consideration in order to develop and test resilient and sustainable biochar-based greenhouse gas mitigation strategies. Adding biochar to sandy or coarse textured soils reduced both N2O emissions and NO3- leaching, which reduces soil N losses and presumably improves both N-use efficiency and mitigates climate change. Our results provide a valuable starting point for future biochar-based N loss mitigation studies.

Technical Abstract: Biochar can reduce both nitrous oxide (N2O) emissions and nitrate (NO3-) leaching. However, refining biochar’s use for estimating these types of losses remains elusive. For example, biochar properties such as ash content and labile organic compounds may induce transient effects that alter N-based losses. Thus, the aim of this meta-analysis was to assess interactions between biochar-induced effects on N2O emissions and NO3- retention, regarding duration of experiment as well as soil and land use properties. Data were compiled from 88 peer-reviewed publications resulting in 701 observations up to May 2016 and corresponding response ratios used to perform a random effects meta-analysis, testing biochar's impact on cumulative N2O emissions, soil NO3- concentrations and leaching. The overall N2O emissions reduction was 38 percent (%), but N2O emission reductions tended to be negligible after one year. Overall, soil NO3- concentrations remained unaffected while NO3- leaching was reduced by 13% with biochar; greater leaching reductions (>26%) occurred over longer experimental times (i.e. >30 days). Biochar had the strongest N2O-emission reducing effect in paddy soils (Anthrosols) and sandy soils (Arenosols). The use of biochar reduced both N2O emissions and NO3- leaching in arable farming and horticulture, but it did not affect these losses in grasslands and perennial crops. In conclusion, the time-dependent impact on N2O emissions and NO3- leaching is a crucial factor that needs to be considered in order to develop and test resilient and sustainable biochar-based N loss mitigation strategies. Adding biochar to sandy or coarse textured soils (e.g. Arenosols) reduced both N2O emissions and NO3- leaching, which reduces soil N losses and presumably improves both N use efficiency and mitigates climate change. Our results provide a valuable starting point for future biochar-based N loss mitigation studies.