Monitoring of Agricultural Hydrodynamics and Investigation of Geophysical Relationships in African Alfisols using Electrical Resistivity Tomography

Russell Swift,Murray Lark,Elijah Phiri,Paul Wilkinson,Arnaud Watlet,Frédéric Nguyen,Phil Meldrum,Joseph Chimungu,Harry Harrison,Tongai Mtangadura,Innocent Sandram,Jimmy Boyd,Jonathan Chambers

doi:10.5194/egusphere-egu22-8137

Abstract

&lt;p&gt;A full understanding of the moisture regimes in agricultural soils is critical when considering a climatic future that is potentially both drier and hotter. The study of near-surface hydrodynamics necessitates a high temporal frequency of measurements to allow the capture of fast-moving processes. In addition to this, heterogeneities in soils, coupled with spatially variable moisture contents, mean that point sensors alone can miss valuable information when studying soil hydrodynamics.&lt;/p&gt;&lt;p&gt;The sensitivity of Electrical Resistivity Tomography (ERT) to soil water content means that it is ideally suited to studying soil hydrodynamics. As a non-invasive technique, it is able to effectively capture spatial heterogeneities, while repeating ERT measurements at short time intervals enables the monitoring of rapid soil moisture changes.&lt;/p&gt;&lt;p&gt;In order to study Conservation Agriculture (CA) - an agricultural technique shown to have increased water and heat stress resilience - we collect frequent ERT measurements (&amp;#8804; daily) over a long period of time (&gt; 2 years) using PRIME - a low-cost, low-power, ERT monitoring instrument developed by the British Geological Survey. Our equipment is permanently installed at three agricultural observatories in southern Africa (Malawi, Zimbabwe, and Zambia), and is complemented by many co-located point sensors monitoring soil temperature, water content, and matric potential.&lt;/p&gt;&lt;p&gt;We compare the hydrodynamics - derived from ERT data - found under CA, with those under conventional agricultural tillage methods, to better understand the root of CA&amp;#8217;s resilience to hot and dry weather conditions. We use laboratory measurements together with the high number of co-located point sensor measurements to build pedological / geophysical relationships for each site, comparing those derived from laboratory scale samples to those derived from in-field measurements.&lt;/p&gt;

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