Carboxylated nanocellulose superabsorbent polymers (SAP) can be used to increase soil water retention in agriculture. The benefits investigated are influenced by the superabsorbent structure, composition and application rate.
In this study, TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl)-oxidised nanocellulose superabsorbents were prepared using three different drying techniques: freeze-dried, and oven-dried at low and high temperatures. The swelling capacity in soil water extracts was measured and compared to deionised water. Soil was amended with different application rates of these superabsorbents to evaluate the effects on water retention, microbial community and their biodegradation.
The absorption performance of nanocellulose superabsorbents is affected by the concentration and type of salts in the soil water extracts. Oven-dried at 50°C SAP presents the highest ionic sensitivity attributed to its large number of accessible carboxylate groups. The water retention of the soil treatments increases with increasing application rate. Soil treated with the freeze-dried superabsorbent shows the highest water retention, whereas those amended with the 50°C oven-dried SAP remain moist the longest. The biodegradation rate of these materials depends on the application rate and nutrient availability. Carboxylated nanocellulose superabsorbents emerge as high-performance biodegradable materials for agricultural use, able to replace the current non-biodegradable petrochemical-based superabsorbents.