Synthesis of xylan and lignin based hydrogels and their use as growth media for rice ( Oryza sativa )

Abstract

Different hydrogels were synthesized using lignin and xylan (extracted from rice straw) as the raw material, PVA as matrix template, citric acid, and succinic acid as crosslinkers and were structurally characterized by FT-IR and SEM analysis. Citric acid cross-linked hydrogels caused loose bonding between polymers and resulted in formation of large pores whereas succinic acid cross-linked hydrogels were observed to have less porosity and tight bonding network. The swelling ratio and reswelling capacity of hydrogels revealed that lignin hydrogels outperformed all other hydrogels. All the synthesized hydrogels were tested for their use as soil culture media ingredient for the germination of rice seedlings. All the hydrogels performed well in stress conditions as compared to normal conditions. Xylan/lignin hydrogel and lignin hydrogels performed best under stress conditions. These hydrogels could be used effectively as an ingredient of soil culture media owing to their tendency to absorb and retain water properly.

An Overview of Polymeric Hydrogel Applications for Sustainable Agriculture

“…Indeed, the first reported use of polyacrylamide for plant growth stabilization of road embankments was in France, where arid, barren soil was converted into established vegetation [103,104]. According to Barakat et al [105], some polymers can be used to overcome problems with traditional irrigation techniques, where hydrogel polymers can serve as a reservoir in the central part of the root zone and prevent water loss through percolation [106,107].…”

“…Hydrogels cross-linked with citric acid exhibited wide pores and loose polymer bonds, whereas hydrogels cross-linked with succinic acid displayed decreased porosity and a tight bond network. With a swelling rate ranging from 0.21 to 0.40 and a resurgent capacity, the lignin hydrogels performed better than any other hydrogel [98,107].…”

“…For example, the new hydrogel made of biopolymers based on acidic whey and cellulose derivatives and polyvinyl alcohol (PVA) was processed by Fabian et al [107] to create an environmentally friendly soil additive that increases the capacity of the soil for retaining water. According to the PVA content and cross-linking density, the significant swelling characteristics of the hydrogels were revealed by the results.…”

“…Hydrogels cross-linked with citric acid exhibited wide pores and loose polymer bonds, whereas hydrogels cross-linked with succinic acid displayed decreased porosity and a tight bond network. With a swelling rate ranging from 0.21 to 0.40 and a resurgent capacity, the lignin hydrogels performed better than any other hydrogel[98,107].Recently, Zhan et al (2024) created conductive hydrogel as a solenoid valve controller for smart irrigation to accomplish on-demand irrigation and more intuitive soil moisture monitoring. Na 2 SO 3 -APS (ammonium persulfate) was utilized as an initiator to create the smart poly(acrylic acid-co-N-methylolacrylamide)/poly(3,4-ethylenedioxythiophene): polystyrene sulfonate hydrogel with double network under mild conditions.…”