Nitrogen turnover and N2O/N-2 ratio of three contrasting tropical soils amended with biochar

Author(s):Show less -

Fungo, Bernard ^{[1, 2, 3]} ; Chen, Zhe ^[4] ; Butterbach-Bahl, Klaus ^{[4, 5]} ; Lehmannn, Johannes ^[6] ; Saiz, Gustavo ^{[4, 7]} ; Braojos, Victor ^[4] ; Kolar, Allison ^[4] ; Rittl, Tatjana F. ^{[4, 8]} ; Tenywa, Moses ^[9] ; Kalbitz, Karsten ^{[2, 10]} ; Neufeldt, Henry ^{[3, 11]} ; Dannenmann, Michael ^[4]

Affiliation:Show less -

^[1] NARO, POB 1752, Kampala - Uganda

^[2] Univ Amsterdam, IBED, Fac Sci, Sci Pk 904, Amsterdam - Netherlands

^[3] World Agroforestry Ctr ICRAF, POB 30677, United Nations Ave, Nairobi 00100 - Kenya

^[4] KIT, Atmospher Environm Res IMK IFU, Inst Meteorol & Climate Res, Kreuzeckbahnstr 19, D-82467 Garmisch Partenkirchen - Germany

^[5] ILRI, POB 30709, Nairobi 00100 - Kenya

^[6] Cornell Univ, Dept Crop & Soil Sci, Bradfield Hall, Ithaca, NY 14853 - USA

^[7] Univ Catolica Concepcion UCSC, Dept Quim Ambiental, Concepcion - Chile

^[8] Univ Sao Paulo, Dept Soil Sci, Ave Padua Dias, POB 9, Piracicaba - Brazil

^[9] Makerere Univ, CAES, POB 7062, Kampala - Uganda

^[10] Tech Univ Dresden, Inst Soil Sci & Site Ecol, Soil Resources & Land Use, PiennerStr 19, D-01737 Tharandt - Germany

^[11] UNEP DTU Partnership, Copenhagen - Denmark

• Document type: Journal article
• Source: Geoderma; v. 348, p. 12-20, AUG 15 2019.
• Web of Science Citations: 0

Abstract

Biochar has been reported to reduce emission of nitrous oxide (N2O) from soils, but the mechanisms responsible remain fragmentary. For example, it is unclear how biochar effects on N2O emissions are mediated through biochar effects on soil gross N turnover rates. Hence, we conducted an incubation study with three contrasting agricultural soils from Kenya (an Acrisol cultivated for 10-years (Acrisol10); an Acrisol cultivated for over 100-years (Acrisol100); a Ferralsol cultivated for over 100 years (Ferralsol)). The soils were amended with biochar at either 2% or 4% w/w. The N-15 pool dilution technique was used to quantify gross N mineralization and nitrification and microbial consumption of extractable N over a 20-day incubation period at 25 degrees C and 70% water holding capacity of the soil, accompanied by N2O emissions measurements. Direct measurements of N-2 emissions were conducted using the helium gas flow soil core method. N2O emissions varied across soils with higher emissions in Acrisols than in Ferralsols. Addition of 2% biochar reduced N2O emissions in all soils by 53 to 78% with no significant further reduction induced by addition at 4%. Biochar effects on soil nitrate concentrations were highly variable across soils, ranging from a reduction, no effect and an increase. Biochar addition stimulated gross N mineralization in Acrisol-10 and Acrisol-100 soils at both addition rates with no effect observed for the Ferralsol. In contrast, gross nitrification was stimulated in only one soil but only at a 4% application rate. Also, biochar effects on increased NH4+ immobilization and NO3- consumption strongly varied across the three investigated soils. The variable and bidirectional biochar effects on gross N turnover in conjunction with the unambiguous and consistent reduction of N2O emissions suggested that the inhibiting effect of biochar on soil N2O emission seemed to be decoupled from gross microbial N turnover processes. With biochar application, N-2 emissions were about an order of magnitude higher for Acrisol-10 soils compared to Acrisol-100 and Ferralsol-100 soils. Our N2O and N-2 flux data thus support an explanation of direct promotion of gross N2O reduction by biochar rather than effects on soil extractable N dynamics. Effects of biochar on soil extractable N and gross N turnover, however, might be highly variable across different soils as found here for three typical agricultural soils of Kenya. (AU)

• FAPESP's process: 17/00921-0 - Long-term effects of biochar application on soil carbon sequestration and greenhouse gases emissions under different environmental and experimental conditions
• Grantee: Tatiana Francischinelli Rittl
• Support Opportunities: Scholarships abroad - Research Internship - Post-doctor