Fig. 3: The water-saving capacity of SPWH technologies in greenhouses.
a Water holding capacity of different SPWHs47,48,49,51,53,54. SAH super-absorbent hydrogel, OK-PAA4 okara-poly (acrylic acid) superabsorbent hydrogels, SH-20RHA superabsorbent hydrogel composite based on the biopolymer starch, and 20 wt% rice husk ash. C-P3-MMT2 carrageenan/psyllium sodium/montmorillonite clay hydrogels, WS3-CA4% wheat straw modified hydrogel crosslinked with 4% citric acid, Gel-1-SN single-network hydrogel. b Soiling water increasing capacity of different SPWHs47,48,49,51,53,54. c SPWHs needed for different crops for their entire growth period without irrigation. Taking SAH as an example of SPWHs. The irrigation needs of corps are taken from refs. 8,9. d Schematic illustration of self-watering SPWHs. Passive water irrigation: At night, SPWHs absorb atmospheric moisture and release it as liquid water into the soil, passively irrigating plants. Solar-powered humidification: During the day, sunlight drives water evaporation from SPWHs, increasing humidity and helping retain soil moisture. e Schematic illustration of adding nutrition in SPWHs before bleeding. No more irrigation is needed during the entire crop growth period.
