Open AccessReactive Transport of Manure‐Derived Nitrogen in the Vadose Zone: Consideration of Macropore Connectivity to Subsurface Receptors
Author(s) -
Hussain Syed I.,
Frey Steven K.,
Blowes David W.,
Ptacek Carol J.,
Wilson David,
Mayer K. Ulrich,
Su Danyang,
Gottschall Natalie,
Edwards Mark,
Lapen David R.
Publication year - 2019
Publication title -
vadose zone journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.036
H-Index - 81
ISSN - 1539-1663
DOI - 10.2136/vzj2019.01.0002
Subject(s) - macropore , tile drainage , loam , tile , soil water , vadose zone , soil science , environmental science , soil horizon , hydrology (agriculture) , chemistry , geology , materials science , geotechnical engineering , mesoporous material , biochemistry , composite material , catalysis
Core Ideas Manure N transformation was modeled with different soil pore connectivities to tile drains. Macropores facilitated NH 4 + oxidation reaction products deeper in the profile. Nitrate losses to tile were best predicted by models using pores connected to tile drains. Macropores can be important conduits for surface‐derived nutrients to reach subsurface receptors. Accordingly, nutrient reactive transport processes in macroporous soils need to be well understood. In this study, steady‐state two‐dimensional reactive transport simulations with MIN3P‐THCm (version 1.0.519.0) were used to elucidate how soil macropore connectivity to tile drains can influence N transformations following liquid swine manure (LSM) applications to soil. Four different soil scenarios were considered: homogeneous sand, homogeneous clay loam, and clay loam with discrete macropores connected to or disconnected from the bottom boundary used to represent tile drain outflow. In relation to the homogeneous soils, macropores, overall, facilitated chemical diffusion into the adjacent soil matrix along their length and broadly augmented O 2 ingress into the soil profile. These processes combined to critically control the spatial distribution of NH 4 + oxidation reaction products. When used in transient simulation mode with field data observed at experimental tile‐drained plots that received LSM application, the model showed that simulated nitrate mass losses to tile are considerably higher and most realistic under the connected macropore scenario compared with the homogeneous or disconnected macropore scenarios.