Greenhouse Gas Emissions in Continuous Corn As Affected By Soil Tillage and Irrigation Systems.

Soil tillage and irrigation methods may have a significant impact on greenhouse gas (GHG) emissions from agricultural soils. A two-year field experiment (2015-2016) was conducted at the EEAD-CSIC experimental farm in Zaragoza, NE Spain, to assess the effects of three tillage practices (i.e. no-tillage with crop residue retention, NTr; no-tillage without crop residue, NT; and conventional intensive tillage, CT) and two irrigation systems (i.e. sprinkler irrigation, S; and flood irrigation, F) on soil GHG emissions in a continuous corn field. Carbon dioxide (CO₂), nitrous oxide (N₂O) and methane (CH₄) were measured weekly from April to mid-August, every two weeks between mid-August and October and every three weeks from October to April, using static chambers.

Seasonal cumulative CO₂-C emissions were higher in S compared with F during the two years of observation. These differences could be related to the above-ground crop biomass that was higher in S compared with F during both years. In addition, cumulative CO₂-C emissions were significantly affected by tillage during the 2016 growing season, with the greatest value for the CT-S treatment. The F irrigation system had larger losses of N₂O-N than the S system because of the greater soil water content measured in the F system throughout the entire growing season. However, no significant differences in cumulative N₂O-N emissions were observed between tillage treatments over the entire measurement period. The CH₄ emissions showed a similar behavior throughout the experiment, with no significant differences between treatments. Finally, the ratio between global warming potential (GWP) and grain yield was significantly different among irrigation systems, being higher in F for the years 2015 and 2016. This research highlights the relevance of agricultural management, especially the irrigation system, on GHG emissions under Mediterranean conditions.