Details of gelatin-based hydrogels.

Polymers	Synthesis method & cross-linker used	Swelling degree (SD)/water absorption	Agricultural applications	References
Gelatin, acrylic acid, kaolin powder	Graft polymerization (methylenebisacrylamide-cross linker)	85–90 g g−1 at pH = 8	Enhance the water retention capacity of soil (pH-responsive behavior)	57
		55 g g−1 in NaCl solution (maximum)
Gelatin	Chemical cross-linking (glutaraldehyde-cross linker)	218% in distilled water (maximum)	Controlled release of fertilizer enhances the water absorption capacity of soil	58
Gelatin and agar	Chemical cross-linking	636.1% in deionized water (maximum)	Excellent water holding capacity	59
Gelatin, sodium alginate	Ionic gelation method (calcium chloride-cross linker)	13.95 g g−1 in deionized water (maximum)	Controlled release of urea and other nutrients	60
Gelatin	Chemical cross-linking (glutaraldehyde-cross linker)	228–251% in deionized water	Controlled release of urea and other nutrients and fertilizer, water retention, enhanced plant growth	61
Gelatin, di-aldehyde xanthan gum	Chemical cross-linking	—	Allow controlled release of fertilizers, improves water holding capacity of soil	62
Gelatin, polylactic acid and chitosan	Chemical cross-linking	4448% at 30 °C in deionized water	Excellent water retention ability allow the slow release of nitrogen and other useful nutrients	63