Long-term conservation agriculture impact on soil hydrology

Soil core sampling.

In this project, I worked with my Ph.D. advisor, Professor Teamrat Ghezzehei and Professor Jeff Mitchell to determine the effect of 18 years of the conservation agriculture (reduced disturbance tillage and cover cropping) on soil structural and hydraulic properties. The study site was located at the University of California West Side Research and Extension Center in Five Points, California. The soils’ water conductivity and retention properties were measured in laboratory using KSAT and HYPROP functions. Soils’ water storage and retention were further evaluated using numerical simulations in HYDRUS.

Cover crop and no-cover crop plots

Some of our key findings were that changes in pore size distribution and conductivity associated with reduced tillage and cover cropping improved soil structure and increased infiltration rate and soil water retention at unsaturation. Both reduced tillage and cover cropping reduced soil water content at field capacity (-33 kPa suction) and plant available water content as determined in the laboratory. However, numerical simulations of irrigated tomatoes across the irrigated season showed that reduced tillage and cover cropping potentially increased soil profile water storage and water availability. This result highlights the weakness of using static laboratory-measured properties to evaluate soil hydrology.

pore-size-distribution

This project is partly published in chapter three of my dissertation and is currently in preparation for publication in a peer-reviewed journal.

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Samuel N Araya
Postdoctoral Research Fellow

My research interests include soil science, machine learning and spatial analysis.