Thermosensitive biodegradable hydrogels for soil regeneration under changing climate conditions

This study evaluated the performance of a thermosensitive, biodegradable biocomposite hydrogel in improving the regulation of soil water, the availability of nutrients, microbial activity, and biological recovery in degraded agricultural soils under arid climatic conditions. The research was conducted over two consecutive growing seasons (2023-2025) in Zharma District, East Kazakhstan. The hydrogel, synthesised from cellulose-derived components including microcrystalline cellulose, carboxymethylcellulose, and hydroxyethylcellulose, was applied to field plots at an optimal rate of 30 g m⁻² using a randomised complete block design with five replicate plots per treatment. Laboratory characterisation revealed the following properties: high water absorption capacity (167.0 ± 4.1%), water release capacity (72.1 ± 1.8%), biodegradation occurring over a period of 6.07 ± 0.42 months, a mass loss of 71.6 ± 1.8% and a tensile strength of 2.49 ± 0.22 MPa. Compared with untreated controls, field application significantly improved soil physicochemical properties, increasing soil moisture from 79.6% ± 5.3% to 95.1% ± 2.6%, organic matter content from 2.21% ± 0.41% to 3.06% ± 0.53%, nitrate concentration from 34.0% ± 5.2% to 54.8% ± 5.9%, phosphate concentration from 11.4% ± 3.6% to 19.6% ± 3.9% and potassium concentration from 108.5% ± 13.8% to 151.5% ± 12.2% (all p < 0.001). The application of hydrogel also stimulated soil microbial activity, increasing the abundance of ammonifying bacteria, oligotrophs, cellulolytic bacteria, actinomycetes and CO₂ respiration. Furthermore, soils treated with hydrogels showed improved biological recovery, with higher earthworm abundance (41.3 ± 5.2 vs. 29.7 ± 3.9 individuals per m²), biomass (18.3 ± 1.8 vs. 12.5 ± 2.3 g per m²) and a higher Shannon diversity index (2.48 ± 0.21 vs. 1.73 ± 0.19) than controls (p < 0.001). These results suggest that thermosensitive biocomposite hydrogels can improve soil quality, promote biological activity, and aid the sustainable restoration of degraded agricultural ecosystems in regions with limited water resources.