Skip to main navigation menu Skip to main content Skip to site footer
Plant Science Today (PST)

Research Articles

Early Access

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
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.

References

  1. 1. Jordán A, Zavala LM. Soil structure and hydrological processes in Mediterranean agroecosystems: A review. Geoderma. 2024;431:116380. https://doi.org/10.1016/j.geoderma.2023.116380
  2. 2. Six J, Bossuyt H, Degryze S, Denef K. A history of research on the link between (micro) aggregates, soil biota and soil organic matter dynamics. Soil Tillage Res. 2004;79(1-2):7–31. https://doi.org/10.1016/j.still.2004.03.008
  3. 3. Bronick CJ, Lal R. Soil structure and management: A review. Geoderma. 2005;124(1-2):3–22. https://doi.org/10.1016/j.geoderma.2004.03.005
  4. 4. Pagliai M, Vignozzi N, Pellegrini S. Soil structure and the effect of management practices. Soil Tillage Res. 2004;79(2):131–43. https://doi.org/10.1016/j.still.2004.07.002
  5. 5. Kemper WD, Rosenau RC. Aggregate stability and size distribution. In: Klute A, editor. Methods of soil analysis: Part 1—Physical and mineralogical methods. 2nd ed. Madison (WI): ASA and SSSA; 1986. p. 425–42.
  6. 6. Reynolds WD, Elrick DE, Youngs EG. Constant head soil core (tank) method. In: Dane JH, Topp GC, editors. Methods of soil analysis: Part 4—Physical methods. Madison (WI): SSSA; 2002. p. 804–8.
  7. 7. Walkley A, Black IA. An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method. Soil Sci. 1934;37(1):29–38. https://doi.org/10.1097/00010694-193401000-00003
  8. 8. Gee GW, Or D. Particle-size analysis. In: Dane JH, Topp GC, editors. Methods of soil analysis: Part 4—Physical methods. Madison (WI): SSSA; 2002. p. 255–93.
  9. 9. Lipiec J, Hatano R. Quantification of compaction effects on soil physical properties and crop growth. Geoderma. 2003;116(1-2):107–36. https://doi.org/10.1016/S0016-7061(03)00097-1
  10. 10. Blanco-Canqui H, Ruis SJ. No-tillage and soil physical environment. Geoderma. 2020;366:114204. https://doi.org/10.1016/j.geoderma.2019.114200
  11. 11. Abdollahi L, Munkholm LJ. Tillage and soil structure: A review. Soil Sci Soc Am J. 2022;86(1):1–18. https://doi.org/10.1002/saj2.20400
  12. 12. Basche AD, DeLonge MS. Comparing infiltration rates in soils managed with conventional and alternative farming methods: A meta-analysis. PLoS One. 2019;14(9):e0222379. https://doi.org/10.1371/journal.pone.0222379
  13. 13. Głąb T, Żabiński A, Sadowska U, Gondek K. Effects of conservation tillage on soil hydraulic properties. Soil Tillage Res. 2020;204:104714. https://doi.org/10.1016/j.still.2020.104714
  14. 14. Rosseel Y. lavaan: An R package for structural equation modeling. J Stat Softw. 2012;48(2):1–36. https://doi.org/10.18637/jss.v048.i02

Downloads

Download data is not yet available.