How efficient is film fully-mulched ridge–furrow cropping to conserve rainfall in soil at a rainfed site?

• FMFR effects were assessed with and without maize planting.
• Mulch conserved 100 mm more rainfall in soil in one season than no mulch.
• Increased transpiration induced the varied mulch effects on soil–water storage.
• Increased transpiration contributed to the increased yield and WUE under mulch.

The present reported study was designed to assess the interactive effects between film fully-mulched ridge–furrow (FMRF) cropping and the presence of a crop on soil moisture. Four treatments were evaluated in 2011 and 2012 at a rainfed semi-arid site: (1) no mulch + no crop planting, (2) mulch + no crop planting, (3) no mulch + crop planting, and (4) mulch + crop planting. Narrow and wide ridges were alternated in all treatments and maize (Zea mays L.) was seeded in furrows only for the crop planting treatments. In 2011, soil water storage in the 0–100 cm layer was higher at all measurements after sowing under mulched compared to unmulched treatment with no maize planting, whereas it increased at measurements in the first two and a half months only under mulched compared to unmulched treatment with maize planting. This indicated that the effect of mulch on soil–water storage was associated with increased transpiration. Mulch under no maize planting increased water storage to the field holding capacity by the end of one growing season, conserving 100 mm more water in the 0–170 cm layer than no mulch. This highlighted that FMRF was very efficient at conserving rainwater in soil. In 2012, soil moisture dynamics under the four treatments were different from those in 2011 because of residue effects and higher precipitation. Compared to no mulch, mulch increased grain yield and water use efficiency by 70–72% and 57–77%, respectively, over the two experiment years. The results suggest that increased transpiration under mulch contributes to increased grain yield and water use efficiency compared with no mulch.