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Plant Science Today (PST)

Research Articles

Vol. 13 No. 3 (2026)

Mean weight diameter as an integrative soil health indicator of hydraulic conductivity and wheat yield under conservation agriculture in drylands

DOI
https://doi.org/10.14719/pst.13863
Submitted
27 January 2026
Published
02-07-2026 — Updated on 09-07-2026
Versions

Abstract

The stability of soil aggregates governs macropore connectivity, which regulates saturated hydraulic conductivity (Ks), root penetration and water use efficiency in semi-arid soils. The mechanistic role of mean weight diameter (MWD) as a structural indicator linking soil aggregation to hydraulic conductivity and crop performance across contrasting soil textures and management durations remains unquantified. This study evaluated long-term conservation agriculture (CA) systems on two contrasting soil types in northern Iraq: an 11 year system on a clay loam and a 5 year system on a silty loam. Conservation agriculture increased MWD by 21–61 %, Ks by 85–116 % and wheat grain yield by 15–25 % relative to conventional tillage. Across soils, MWD explained 89 % of the variance in Ks (R² = 0.89, p < 0.001) and 84 % of the variance in grain yield (R² = 0.84, p < 0.001). Path analysis supported evidence for yield gains being physically mediated by MWD-driven enhancements in Ks and deeper root penetration (49–68 %), with soil texture moderating the strength of the MWD–yield relationship. These findings establish MWD as a measurable structural state variable governing soil hydraulic function and root–soil interactions, providing a mechanistic basis for its inclusion in soil health assessment frameworks for water-limited cropping systems.

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