Biodegradability of bio-based and synthetic hydrogels as sustainable soil amendments: A review

Superabsorbent polymers (SAPs), sometimes known as hydrogels, have been proposed as soil amendments to enhance soil water management. But the performance of SAPs as soil amendments depends on their stability in soil. Bio-based SAPs have been praised as environmentally sustainable due to their apparent fast biodegradation relative to synthetic SAPs. But the fast biodegradation of bio-based SAPs may come at a cost to their long-term performance for repeated absorption and release of water in the soil. The purpose of this review is to (i) concisely summarize the methods and mechanisms involved in the biodegradation of different bio-based and synthetic SAPs, (ii) critically review studies conducted on the biodegradability of bio-based and synthetic SAPs when used as soil amendments, and (iii) discuss the implications of the biodegradability of bio-based and synthetic SAPs on their physical properties and stability in soil and (iv) identify potential research directions. Understanding the biodegradability of synthetic compared to bio-based SAPs and their advantages and disadvantages as soil amendments is important to researchers and farmers when choosing a specific type of SAPs as an agricultural soil amendment.