Nature-Inspired Superhydrophobic Sand Mulches Increase Agricultural Productivity and Water-Use Efficiency in Arid Regions

Excessive evaporative loss of water from the topsoil in arid-land agriculture is compensated via irrigation that exploits massive freshwater resources. The cumulative effects of decades of unsustainable freshwater withdrawals in many arid regions are now threatening food-water security. While plastic mulches can reduce evaporation from the topsoil, their cost and nonbiodegradability limit their utility. In response, we report on biodegradable superhydrophobic sand (SHS), a bioinspired enhancement of common sand with a nanoscale wax coating. When SHS was applied as a 5-10 mm-thick mulch over the soil, evaporation was reduced by 56-78% and soil moisture increased by 25-45%, which benefited the development of crops. Multiyear field trials with tomato (Solanum lycopersicum), barley (Hordeum vulgare), and wheat (Triticum aestivum) under normal irrigation demonstrated that SHS mulch application enhanced yields by 17-73%. Under brackish water irrigation (5500 ppm NaCl), SHS mulching produced 53-208% higher fruit and grain yields for tomato and barley crops, respectively. SHS application did not affect the soil-root-rhizosphere microbial communities as evidenced by 16S rRNA gene analysis. The rhizospheric environments were dominated by an assemblage of diverse bacterial communities, such as Gammaproteobacteria, Alphaproteobacteria, and Bacteroidetes, followed by Firmicutes, Gemmatimonadetes, and Actinobacteria, which could be responsible for the degradation of paraffin wax on the SHS. Thus, SHS technology should benefit irrigated agriculture and city-greening efforts in arid regions under the constraint of high water-use efficiency.