Greenhouse gas emissions and crop yield in no-tillage systems: A meta- analysis

No-tillage (NT) has been touted as one of several climate-smart agriculture (CSA) management practices that improve food security and enhance agroecosystem resilience to climate change. However, the sustainable effectiveness of NT greatly depends on trade-offs between NT-induced changes in crop yield and greenhouse gas (GHG, i.e. CH4, CO2, and N2O) emissions. Such trade-offs are regulated by climate fluctuations and heterogeneous soil conditions and have not been well addressed. Supporting CSA management decisions requires advancing our understanding of how NT affects crop yield and GHG emissions in different agroecological regions. In this study, a meta-analysis was conducted using 740 paired measurements from 90 peer-reviewed articles to assess the effects of NT on crop yield, GHG emissions, and the global warming potential (GWP) of major cereal cropping systems. Compared to conventional tillage (CT), NT reduced in GHG emissions and increased crop yield in dry, but not humid, climates, and reduced in the GWP at sites with acidic soils. Across different cropping systems, NT enhanced barley yield by 49%, particularly in dry climates, and it decreased the GWP of rice fields through a 22% reduction in both CO2 and CH4 emissions. Our synthesis suggests that NT is an effective CSA management practice because of its potential for climate change mitigation and crop yield improvement. However, the net effect of NT (relative to CT) was influenced by several environmental and agronomic factors (climatic conditions, tillage duration, soil texture, pH, crop species). Therefore, agroecological setting must be taken into consideration when conducting a comparative evaluation of different tillage practices.