Alleviating Heat Stress and Water Scarcity in Cultivation with Biodegradable Radiative Cooling Mulch

Abstract Agriculture faces pressing challenges of heat stress and water scarcity due to climate change. While mulching is a common solution, traditional mulching materials lack sub-ambient cooling capabilities and biodegradability, resulting in elevated soil temperature, increased moisture evaporation, exacerbated global agricultural heat-water crisis, and soil microplastics pollution. Herein, we have developed a biodegradable and biocompatible ethyl-cellulose radiative cooling mulch with a solar reflectance and thermal emissivity of 97% and 0.93, respectively, to provide zero-energy cooling for soil surfaces. Field tests have demonstrated that the radiative cooling mulch significantly reduces soil moisture evaporation by 60% through cooling soil surfaces, while also improves plant growth by 30% through reducing crop leaf temperature and increasing sunlight exposure for photosynthesis in hot days. Moreover, global heat-water nexus simulations show that the mulch increases soil moisture preservation by over 80% and alleviates agricultural water scarcity by over 60% in arid regions during hot seasons. The work offers an eco-friendly and feasible pathway to foster sustainable agriculture by alleviating heat stress and water scarcity in the context of global warming.