Natural and forced soil aeration during agricultural managed aquifer recharge

Yonatan Ganot,Helen E. Dahlke

doi:10.1002/vzj2.20128

Abstract

AbstractOne 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 O2 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 O2 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% O2 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 O2 demand during Ag‐MAR if flooding duration is controlled according to O2 depletion rates. In large Ag‐MAR projects, forced aeration might be useful to improve local zones of O2 deficiency, which are expected to occur due to topographic irregularities and spatial variability of drainage properties.

Highlights

In recent decades, ubiquitous use of groundwater in California and other parts of the world have led to chronic groundwater overdraft and water quality issues
Maintaining even flooding within the flooded treatments was a difficult task at all sites, it was practically impossible at the Nickels Soil Laboratory (NSL) site due to a combined effect of poor soil drainage and plot slope
Soil aeration is an important parameter in agricultural managed aquifer recharge (Ag-MAR), as prolonged flooding may result in yield loss due to soil O2 deficiency

Summary

Introduction

Ubiquitous use of groundwater in California and other parts of the world have led to chronic groundwater overdraft and water quality issues. As most agricultural fields have lower infiltration capacities compared with dedicated recharge basins, Ag-MAR is designed to capture high-volume excess surface water by flooding large areas of farmland at relatively low recharge rates of less than one meter per Ag-MAR event (Kocis & Dahlke, 2017; Kourakos et al, 2019). Flooding for Ag-MAR is preferably done on fallow fields or during crop dormancy periods, when agricultural fields have the potential to serve as percolation basins for groundwater recharge. O’Geen et al (2015) recommended potential areas in California for Ag-MAR using an index (Soil Agricultural Groundwater Banking Index [SAGBI]) that combines five soil characteristics: deep percolation, root zone residence time, chemical properties, topography, and surface conditions. An ideal Ag-MAR site will comprise an effective deep percolation (beyond the root zone), adequate crop tolerance for flooding, low soil salinity, leveled soil surface, and lack of compaction and erosion. O’Geen et al (2015) identified an area of 22,500 km of agricultural land (31% of the studied area), mostly in the Central Valley, as having excellent to moderately good potential for Ag-MAR

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