Closed‐Loop Radiative Cooling Mulch Upcycled From Agricultural Residues for Efficient Soil Heat–Water Stress Mitigation

Global warming is intensifying coupled heat-water stress in agriculture, necessitating scalable strategies for cooling and moisture retention. Passive radiative cooling (PRC) presents a promising avenue, yet current PRC films predominantly rely on expensive non-agricultural feedstocks and involve energy- or solvent-intensive manufacturing processes, while limited end-of-life environmental compatibility hampers alignment with agricultural systems. Herein, we present a sustainable radiative cooling mulch (SRCM) derived from waste maize leaves, engineered to establish an "agricultural residue-material-soil" closed loop. Through spontaneous hydrogen-bond-mediated self-assembly requiring no external energy, we engineered a hierarchically porous, self-reinforced fibrous network that combines application-grade mechanical robustness (tensile strength up to 17.8 MPa) with a high solar reflectance of 93.3% and a mid-infrared emissivity of 92.6%. In outdoor tests, relative to bare soil, SRCM lowers soil temperature by up to 18°C and suppresses evaporative water loss by up to 85.8%, markedly improving early-stage bok choy growth with 5.3-fold higher germination and 220% greater biomass. Furthermore, SRCM demonstrates excellent recyclability via aqueous reprocessing and exhibits complete biodegradability and biosafety at the end of its life cycle. This work offers a scalable, closed-loop strategy at the heat-water-food-energy nexus, advancing sustainable circular agriculture.