In semi-arid cropping regions where rainfall is variable, stored soil water is important for reducing the impacts of dry periods; however, in-season evaporation limits yield potential. We tested the productivity benefits of protecting wheat and lentil crops from evaporation using inter-row polymer cover, when grown in southern Australia. For wheat, white polyvinyl chloride (PVCw) increased yield by 50% (561 kg/ha) and 11% (408 kg/ha) for decile 2 (2018) and 3 (2019) seasonal rainfall respectively; and for lentil, yield increases were 20% (443 kg/ha) in 2019. A sprayable alginate polymer increased wheat yield by 8% (310 kg/ha). Total water use for wheat in 2018 was reduced (17 mm) for PVCw and water use efficiency (WUE) significantly increased from 7 to 11 kg/ha/mm, whereas in 2019, WU was greater (47 mm) for PVCw, but WUE was equivalent to the control (similar to 15 kg/ha/mm). Colour of the PVC modified the light available to the crop and canopy temperature, where a highly reflective inter-row cover (albedo 0.44) increased wheat yield (similar to 487 kg/ha). For the future, formulations of highly reflective polymers applied in-season within dryland cropping enterprises are likely to provide production advantages, although logistical viability of application and potential environmental implications may define impediments to adoption.