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3 years ago in Hydrology , Physics , Soil Science By Meghana R

Why does water-holding capacity increase as soil structure develops in coarse-textured soils?

My field trials with organic amendments in sandy soils show improved water retention, which we attribute to better structure. But I want to articulate the precise physical reason for my grant report. How does creating aggregates in a sandy matrix actually change the pore geometry to retain more water against drainage?

 

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By Renu Answered 1 year ago

Think of a bare sand as a collection of similar-sized large particles with large pores between them. Water drains quickly by gravity through these macropores. When you improve structure through organic matter addition and biological activity you bind particles into aggregates. This creates a new, dual pore system: macropores between aggregates for drainage and aeration, and micropores within aggregates. These micropores are small enough to hold water tightly via capillary forces, resisting drainage. I've measured this shift in the lab; the improved soil effectively has a greater volume of these small, water-retaining pores

 

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