Influence of irrigation time and frequency on greenhouse gas emissions in a solid-set sprinkler-irrigated maize under Mediterranean conditions

Irrigation management may influence soil greenhouse gas emissions (GHG). Solid-set sprinkler irrigation systems allow to modify the irrigation time and frequency. The objective of this study was to quantify the effect of two irrigation times (daytime, D; nighttime, N)and two irrigation frequencies (low, L; high, H)on soil carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O)emissions in a solid-set sprinkler-irrigated maize (Zea mays L.)field located in NE Spain during 2015 and 2016 growing seasons and the fallow period between growing seasons. Compared with D irrigation, N irrigation increased soil water content (0–5 cm)in both growing seasons. Irrigation management did not affect CH4 emissions and the soil acted as a sink of CH4. Cumulative CO2 emissions were affected by the measurement period (growing season vs fallow)with the greatest values in 2015 growing season, being 81 and 32% higher over the fallow period and over the 2016 growing season, respectively, due to the effect of the preceding crop, alfalfa, and a better soil moisture conditions for the microorganism activity. Similarly, cumulative N2O emissions showed the highest values in 2015, reporting values 90 and 51% greater than the fallow period and the 2016 growing season, respectively. Moreover, N irrigation increased cumulative N2O emissions by 29% compared with D irrigation, but irrigation frequency did not affect cumulative N2O emissions. Irrigation time did not affect cumulative N2O emissions scaled per grain yield or per N uptake because N irrigation increased maize yield by 11% compared with D irrigation. Due to the lack of differences in the scaled N2O emissions, N irrigation should be consider as an appropriate strategy to optimize grain yield without compromising soil GHG emissions per unit of grain yield in Mediterranean agroecosystems.