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Climate, duration, and N placement determine N2O emissions in reduced tillage systems: a meta-analysis

van Kessel, Chris, Venterea, Rodney, Six, Johan, Adviento-Borbe, Maria Arlene, Linquist, Bruce, van Groenigen, Kees Jan
Global change biology 2013 v.19 no.1 pp. 33
arid zones, conventional tillage, fertilizer application, gas emissions, humid zones, long term experiments, meta-analysis, nitrogen fertilizers, nitrous oxide, no-tillage, reduced tillage, soil texture
No-tillage and reduced tillage (NT/RT) management practices are being promoted in agroecosystems to reduce erosion, sequester additional soil C and reduce production costs. The impact of NT/RT on N2O emissions, however, has been variable with both increases and decreases in emissions reported. Herein, we quantitatively synthesize studies on the short- and long-term impact of NT/RT on N2O emissions in humid and dry climatic zones with emissions expressed on both an area- and crop yield-scaled basis. A meta-analysis was conducted on 239 direct comparisons between conventional tillage (CT) and NT/RT. In contrast to earlier studies, averaged across all comparisons, NT/RT did not alter N2O emissions compared with CT. However, NT/RT significantly reduced N2O emissions in experiments >10 years, especially in dry climates. No significant correlation was found between soil texture and the effect of NT/RT on N2O emissions. When fertilizer-N was placed at ≥5 cm depth, NT/RT significantly reduced area-scaled N2O emissions, in particular under humid climatic conditions. Compared to CT under dry climatic conditions, yield-scaled N2O increased significantly (57%) when NT/RT was implemented