The Impacts of Bio-Based and Synthetic Hydrogels on Soil Hydraulic Properties: A Review

Abstract

Soil hydraulic properties are important for the movement and distribution of water in agricultural soils. The ability of plants to easily extract water from soil can be limited by the texture and structure of the soil, and types of soil amendments applied to the soil. Superabsorbent polymers (hydrogels) have been researched as potential soil amendments that could help improve soil hydraulic properties and make water more available to crops, especially in their critical growing stages. However, a lack of a comprehensive literature review on the impacts of hydrogels on soil hydraulic properties makes it difficult to recommend specific types of hydrogels that positively impact soil hydraulic properties. In addition, findings from previous research suggest contrasting effects of hydrogels on soil hydraulic properties. This review surveys the published literature from 2000 to 2020 and: (i) synthesizes the impacts of bio-based and synthetic hydrogels on soil hydraulic properties (i.e., water retention, soil hydraulic conductivity, soil water infiltration, and evaporation); (ii) critically discusses the link between the source of the bio-based and synthetic hydrogels and their impacts as soil amendments; and (iii) identifies potential research directions. Both synthetic and bio-based hydrogels increased water retention in soil compared to unamended soil with decreasing soil water pressure head. The application of bio-based and synthetic hydrogels both decreased saturated hydraulic conductivity, reduced infiltration, and decreased soil evaporation. Hybrid hydrogels (i.e., a blend of bio-based and synthetic backbone materials) may be needed to prolong the benefit of repeated water absorption in soil for the duration of the crop growing season.

NaAlg-g-AA Hydrogels: Candidates in Sustainable Agriculture Applications

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Novel Green Crosslinked Salecan Hydrogels and Preliminary Investigation of Their Use in 3D Printing

“…Taking into consideration the reduction of the swelling degrees at high reactant concentrations, we assume that the increase of the specific surface area of the hydrogel samples is the determinant factor for the samples, which presented smaller pore sizes and higher swelling degrees [ 48 ]. Large specific surfaces of small pores could allow the retention of more fluid due to the higher contact surface between the material and the fluid [ 49 , 50 ]. Certainly, the fluid uptake can be governed by the chemical structure of the samples, their morphology, meaning the porosity together with the specific surface of the pores, or more likely by an input of each.…”

Transforming Sand into Arable Substrate Using Biobased Microgels to Improve Land Productivity

“…Most of the research on hydrogel soil conditioners has focused on combining various polymers and cross-linking techniques to increase their swelling capacity . However, the negative effect of confining stresses in the soil on swelling is often overlooked in the design of these hydrogels. − Based on Louf et al, the swelling pressure generated by hydrogels needs to overcome the confining stress applied by the surrounding soil in order to attain optimum swelling. These confining stresses often exceed the usual swelling pressure that most commercial hydrogels are able to generate, which leads to hindered swelling.…”