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Limiting Water Range: A Case Study for Compacted Subsoils
Author(s) -
PulidoMoncada Mansonia,
Munkholm Lars J.
Publication year - 2019
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2019.01.0023
Subject(s) - subsoil , soil water , compaction , loam , limiting , soil science , environmental science , porosity , soil compaction , hydrology (agriculture) , geology , geotechnical engineering , mechanical engineering , engineering
There is a need for improved knowledge of the limits to the available water range for root growth in the subsoil. The objective of this study was to recalculate the upper and lower limits of the least limiting water range (LLWR) concept by using respectively the air‐filled porosity (ε a ) at which 0.005 of the relative gas diffusivity ( D s /D o ) is reached and readily available water (RAW). The refined upper limit estimates the variation in ε a related to pore connectivity and the refined lower limit expresses the boundary at which plants suffer physiological water stress. This study was based on soil sampled in compaction trials on two sandy loam soils. Soil samples were taken from plots with no compaction (Control), and compaction with 78 kN (M8) and 58 kN (M6) wheel loads with multiple wheel passes. The soil cores were analyzed for ε a , D s /D o , bulk density (ρ b ) and penetration resistance (PR). Heavy farm machinery impact of M8 and M6 led to subsoil compaction up to depth of 0.5 to 0.7 m for the soils under study. The subsoil structure was affected by compaction across depths with the decrease in ε a (∼33–46%) and D s /D o (∼37–61%) and increase in ρ b (∼4–8%) and PR (∼40–50%, at −100 hPa at 30‐cm depth). The refined LLWR showed a wider water range compared to the original approach. We anticipate that the refined LLWR well reflects the limiting soil physical conditions for root growth for the studied soils, but validation by combined soil physical and plant growth measurements is needed. Core Ideas Heavy traffic‐induced compaction narrows LLWR in the subsoil. Air permeability at critical limit of gas diffusivity take in pore organization. Using readily available water as the lower limit represents a drought stress boundary.