Temporal changes in soil hydraulic conductivity in saturated and unsaturated fields

Nishiwaki, J.; Horton, R.

Paddy and Water Environment 18(4): 677-686

2020


ISSN/ISBN: 1611-2490
DOI: 10.1007/s10333-020-00810-x
Accession: 071042741

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Abstract
Soil hydraulic conductivity (K) is an important soil property that exhibits relatively large uncertainty. The temporal variability of K is often ignored when calculating water movement in soil. Various factors such as tillage, rain, temperature, wetting/drying, soil surface crusting, solution concentration, and biological activity can influence field K. We investigated soil K in a central Iowa field as a function of time and tillage by using tension infiltrometer measurements with pressure head tension settings of 0 cm and -3 cm. No clear relationship was found between bulk density (rho(b)) and K. Path analysis was conducted to assess the contribution ratios and causal relationships between factors affecting K. The K values were influenced by physical impacts such as tillage, precipitation, and surface crusting with contributions of 24%, -32%, and 49%, respectively, and with error of 60%. Soil surface crusting had a particularly large impact on saturated K. The maximum volume fraction influenced K. Earthworm activity that impacted the soil pore structure was also noticed in the field. Owing to this biological mechanism, no relationship was observed between rho(b) and K. It is important to recognize the multiple combined effects of soil physical processes and biological activities when documenting K in field soils.