Impact of Hydrogel on Physical Properties of Coarse-structured Horticultural Substrates

Abstract

<jats:p>Addition of a polyacrylamide hydrogel to pine bark and pine bark + sand substrates had no effect on total porosity, regardless of incorporation rate. Container capacity was increased with increasing rate of hydrogel in both substrates. Air space in pine bark was slightly increased at the lowest rate but was reduced with higher incorporation rates. Air space in pine bark + sand was reduced with all hydrogel additions. The dry weigh', of hydrogel cubes recovered from both substrates was similar to amounts predicted. This result indicates that blending hydrogel granules into the substrates was uniform and did not contribute to variability in hydrogel studies. After allowing dry hydrogel granules to expand freely in distilled water for 24 hours, hydrogel granules expanded 317 and 372 times their dry weights at the lowest and highest rates, respectively. Reduction of expansion (in water) at higher rates may have been due to physical restriction of expansion. Conversely, recovered hydrogel cubes from substrates watered to drainage (-10% excess) for 6 weeks absorbed 25 to 55 times their dry weight while in the container. Subsequent rehydration of extracted gels in distilled water was greater for hydrogel cubes from the pine bark + sand medium (104 to 130) than in pine bark alone (51 to 88). Because of anomalies in hydraulic conductivity and pressure plate contact, three techniques were used to study unavailable water content in gels expanded in distilled water. Hydrogel cubes placed in direct contact with the pressure plate released ≈95% of their water at pressures ≤ 1.5 MPa. Effectiveness of ployacrylamide gels in coarse-structured substrates is influenced by physical restrictions to expansion in the substrate and hydraulic conductivity between the hydrogel cubes and the surrounding substrate.</jats:p>

Intrinsic and model polymer hydrogel-induced soil structural stability of a silty sand soil as affected by soil moisture dynamics

“…This might be attributed to the re-swelling of former dehydrated PAA structures by taking up water from the soil pore system and thus decreasing the relatively lower stabilization effects by its intrinsic structural properties and the soil pore water. It has been shown that hydrogels can re-absorb water to a certain degree, even under strongly restricted conditions such as confining particle and suction pressures (Fonteno and Bilderback, 1993;Sannino, 2008;Xu et al, 2006). All in all, although the soil pore water in the treated soil might have contributed to the structural stability as a result of an increased capillarity between the cemented soil particles, the effects of particle cementation and gluing by dehydrated and reswollen PAA structures seemed the predominant reason for the remaining and even re-increased stability after remoistening and additional incubation time of seven days, respectively.…”

Guar gum based biodegradable, antibacterial and electrically conductive hydrogels

“…Hydrogels have been successfully used as soil amendments in agriculture and horticulture industry in order to improve the water-holding capacity and/or nutrient retention of sandy soil [15,16] as comparable to clay or loam [17]. Superabsorbent hydrogels have the potential to influence soil permeability [18], density, structure, texture [19], evaporation [20] and infiltration rates of water through the soils [21].…”

Biohydrogel induced soil–water interactions: how to untangle the gel effect? A review

“…Another method is the application of a matric potential by direct pressure reduction using a water column (Johnson and Veltkamp, 1985). The reproducibility of the results depends on the contact between hydrogel and the suction plate which is not self-evident (Fonteno and Bilderback, 1993). In this context, syneresis effects are an additional problem encountered for low matric potentials.…”