Global warming due to greenhouse gas emissions is currently receiving considerable attention worldwide. Agricultural systems contribute up to 20 % of this global warming. However, agriculture can reduce its own emissions while increasing carbon sequestration through use of recommended management practices, such as consernvation tillage (CT). The objective of this paper is to review the role of long-term CT in mitigating greenhouse gas emissions during corn production in rainfed tropical agro-ecosystems. The types of conservation tillage were no-tillage (NT) and minimum tillage (MT). In a long-term plot study, CO2 emission from CT throughout the corn season was consistently lower than that from intensive tillage (IT). The cumulative CO2 emissions of NT, MT, and IT in corn crops were 1.0, 1.5, and 2.0 Mg CO2-C ha-1season-1, respectively. Soil carbon storage at 0-20 cm depth after 23 years of NT cropping was 36.4 Mg C ha-1, or 43 % and 20 % higher than the soil carbon strorage of IT and MT, respectively. Thus, NT had sequestered some 4.4 Mg C ha-1of carbon amounting to carbon sequestration rate of 0.2 Mg C ha-1 year-1. IT, on the other hand, had depleted soil carbon by as much as 6.6 Mg C ha-1, yielding a carbon depletion rate of 0.3 Mg C ha-1 year-1. Assessment of the farmer's corn fields confirmed these findings. CO2 emission from CT corn farming was similar to that of rubber agroforest and lower than IT corn farming. Based on carbon balance analysis, it can be concluded that corn crops in tropical rainfed agro-ecosystems were not in fact net emitters, and that NT was a better net sinker than other tillage methods. © 2014 The Editor(s) (if applicable) and the Author(s). All rights reserved.
