Shahar Baram - Institute of Soil, Water and Environmental Sciences, Volcani Center, ARO, Rishon Lezion, 7505101, Israel.
Jacob F.Evans - Institute of Soil, Water and Environmental Sciences, Volcani Center, ARO, Rishon Lezion, 7505101, Israel; Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.
Anna Berezkin - Institute of Soil, Water and Environmental Sciences, Volcani Center, ARO, Rishon Lezion, 7505101, Israel.
Meni Ben-Hur - Institute of Soil, Water and Environmental Sciences, Volcani Center, ARO, Rishon Lezion, 7505101, Israel
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 (O2) 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 ∼0.05 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.
