  Excessive evaporative loss of water from the topsoil in arid-land agriculture
is compensated via irrigation, which exploits massive freshwater resources. The
cumulative effects of decades of unsustainable freshwater consumption in many
arid regions are now threatening food-water security. While plastic mulches can
reduce evaporation from the topsoil, their cost and non-biodegradability limit
their utility. In response, we report on superhydrophobic sand (SHS), a
bio-inspired enhancement of common sand with a nanoscale wax coating. When SHS
was applied as a 5 mm-thick mulch over the soil, evaporation dramatically
reduced and crop yields increased. Multi-year field trials of SHS application
with tomato (Solanum lycopersicum), barley (Hordeum vulgare), and wheat
(Triticum aestivum) under normal irrigation enhanced yields by 17%-73%. Under
brackish water irrigation (5500 ppm NaCl), SHS mulching produced 53%-208%
higher fruit yield and grain gains for tomato and barley. Thus, SHS could
benefit agriculture and city-greening in arid regions.
