Natural and forced soil aeration during agricultural managed aquifer recharge

One of the suggested approaches to mitigate the chronic groundwater depletion in California is agricultural managed aquifer recharge (Ag-MAR), in which farmland is flooded using excess surface water in order to recharge the underlying aquifer. Successful implementation of Ag-MAR projects requires careful estimation of the soil aeration status, as prolonged saturated conditions in the rhizosphere can damage crops due to O-2 deficiency. We studied the soil aeration status under almond [Prunus dulcis (Mill.) D.A. Webb] trees and cover crops during Ag-MAR at three sites differing in drainage properties. Water application included several cycles (2-7) and flooding durations (27-63 h) that varied according to the soil infiltration capacity at each site. We used O-2 and redox potential as soil aeration quantifiers to test the impact of forced aeration by air-injection compared with natural soil aeration. Results suggest an average increase of up to 2% O-2 at one site, whereas mixed impact was observed at the two other sites. Additionally, no impact on crop yield was observed for one growing season. Results further suggest that natural aeration can support crop O-2 demand during Ag-MAR if flooding duration is controlled according to O-2 depletion rates. In large Ag-MAR projects, forced aeration might be useful to improve local zones of O-2 deficiency, which are expected to occur due to topographic irregularities and spatial variability of drainage properties.

Automated summary

The study investigated the soil aeration status during agricultural managed aquifer recharge (Ag-MAR) in California, revealing that controlled flooding duration and water application cycles can improve soil aeration and support crop growth. Additionally, forced aeration may be useful in large Ag-MAR projects to address localized oxygen deficiency zones caused by topographic irregularities and drainage property variability.