Hydrogel application for improving soil pore network in agroecosystems. Preliminary results on three different soils

Superabsorbent hydrogels are three-dimensional macromolecular compounds that can absorb and retain large amounts of water. One benefit of amending soils with hydrogels includes better soil structure (i.e., pore network), which can lead to an increase in the retention of water and nutrients, and thus improve crop yield. The objectives of this study were to 1) evaluate the effect of superabsorbent hydrogels on the specific porosity and pore size distribution of three soils and 2) estimate soil swelling from HG application. Two hydrogels (polyacrylate “CI” and cellulose-based “H30”) were used in a randomized complete block design with three soil types (sand (S), sandy loam (SL), and clay (C)), three treatments (CI, H30, and CTRL (control)), with three replicates each. Specific porosity and pore size distribution were measured with three techniques (gas adsorption, mercury intrusion porosimetry, and x-ray computed microtomography) measuring a pore diameter range from 0.4 nm to 2163 µm. Our results showed that while not always significant, HG amended soils had an overall increased porosity >12% regarding macroporosity (i.e., pores >828 µm) compared to the CTRL treatment. Both HGs caused soil volume change from −37% (shrinkage) to 6% (swelling); however, H30 caused significantly lower rates compared to CI, possibly due to soil-like substances incorporated into the H30 structure. Because of this, further studies investigating the interaction between different moisture contents and H30 should be conducted to determine if H30 helps to maintain soil structure.