Influence of drip and furrow irrigation systems on nitrogen oxide emissions from a horticultural crop

Irrigation management has an important influence on emissions of nitrous oxide (N2O) and nitric oxide (NO) from irrigated agricultural soils. In order to develop strategies to reduce the emission of these gases, a field experiment was carried out to compare the influence of different irrigation systems: furrow (FI) and drip-irrigation (DI), on N2O and NO emissions from a soil during the melon crop season. Two fertilizer treatments were evaluated for each irrigation regime: ammonium sulphate (AS) as a mineral N fertilizer, at a rate of 175 kg N ha-1; and a control without any N fertilizer (Control). On plots where the AS treatment was applied, drip irrigation reduced total N2O and NO emissions (by 70% and 33% respectively) with respect to values for furrow irrigation. This was probably due to the lower amount of water applied and the different soil wetting pattern associated with DI. Dry areas of the drip-irrigated plots emitted a similar amount of N2O to the wet areas (0.45 kg N2O-N ha-1) in the Control and greater quantities in the AS treatment (0.92 kg N2O-N ha-1 for dry and 0.70 kg N2O-N ha-1 for wet areas). We suggest that the N oxide pulses observed throughout the irrigation period on DI plots could have been the result of frequent increases in the soil wetting volume after the addition of water. Denitrification losses (from depths of 0-10 cm) were estimated at 11.44 kg N2O- N ha-1 for the AS treatment under FI and at 4.96 kg N2O-N ha-1 for DI. Under DI, nitrification was an important source of N2O, whereas denitrification was the most important source under FI. The addition of NH4+ and the use of DI enhanced the N2O/N2 ratio of gases produced through denitrification. The quantity of dissolved organic C (DOC) in the soil generally decreased with addition of NH4+. This work showed that, in comparison with furrow irrigation, drip irrigation is a method that can be used to save water and mitigate emissions of the atmospheric pollutants NO and N2O.