Subsurface Drip Irrigation Reduced Nitrous Oxide Emissions in a Pomegranate Orchard

Abstract

Soil fertilization is one of the major sources for nitrous oxide (N2O) emissions and soil moisture is among the most important factors affecting its production. Thus, one of the important mitigation strategies in semiarid or arid regions is through irrigation and/or fertigation management. The objective of this research was to evaluate the effects of different drip irrigation methods and N application levels on N2O emissions. Nitrous oxide emission flux and N2O concentration in soil profile were measured in a pomegranate field for two growing seasons under two irrigation systems [subsurface drip irrigation (SDI) at ~0.5 m depth and traditional surface drip irrigation (DI)], and three N application rates (50%, 100%, and 150% of current practice rate). Both years’ data showed that N2O emissions has a high and positive correlation with N fertilization events and application levels. Nitrous oxide emissions from DI at 100% and 150% N levels were over an order of magnitude higher compared to those from SDI based on the data of the first year. Data from the second year confirmed the first year’s findings of high emissions from DI. A positive linear correlation between the N2O emission flux and N2O concentration in soil-gas phase was identified that supported emission data. This research demonstrated that although N fertilization is a major cause for N2O emissions, subsurface drip irrigation/fertigation can lead to a significant emission reduction in addition to other benefits, such as increased water and nutrient use efficiencies, and reduced weed pressure.