Irrigation with treated wastewater containing nanobubbles to aerate soils and reduce nitrous oxide emissions

The objective of the present study was to examine whether we could improve the aeration of clayey soils that had been degraded by long-term irrigation with treated wastewater (TWW) through drip irrigation with TWW aerated with oxygen (O-2) nanobubbles (ONB). A lysimeter set-up was irrigated using surface and subsurface drip systems, and the effects of those systems on soil oxygen concentration, nitrogen transformations, nitrous oxide (N2O) emissions, and crop yield were investigated. In the surface drip system, irrigation with ONB-aerated TWW increased soil oxygen concentrations from 15.6% to 19.7% (p = 0.0001). In the subsurface drip system, soil oxygen concentrations increased from 18.2% to 19.2% (p = 0.0266). In all treatments, nitrate was the dominant N form in the root zone porewater (soil solution) and leachates. Nitrite concentrations were low in all treatments (<4 mg L-1), yet a clear daily accumulation pattern (from similar to 0.05 to similar to 1.0 mg L-1) was observed in the ONB-aerated treatments. Irrigation with ONB-aerated TWW reduced cumulative N2O emissions by 37% in the surface irrigation system and 14% in the subsurface irrigation system. Our results imply that irrigation with ONB-aerated TWW may be an effective way to improve soil aeration, especially in clayey soils that have been degraded by prolonged irrigation with TWW. Such practices may reduce N2O production and the overall N leakiness of agricultural activity. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

This study aimed to improve soil aeration, nitrogen transformations, nitrous oxide emissions, and crop yield by using drip irrigation with oxygen nanobubbles (ONB) aerated treated wastewater (TWW) in clayey soils. The research found that nitrate was the dominant nitrogen form, with ONB treatment reducing nitrous oxide emissions. Results suggest that ONB-aerated TWW irrigation could effectively enhance soil aeration, reduce N2O emissions, and nitrogen leachiness in agricultural activities.