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

ABSTRACT 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.