and WUE was greatly
influenced by the ratio of ridge and furrow when RFRHS was combined with gravel–sand mulch. Watermelon
yield was highest for the 1:1 ratio, and WUE was highest for the 5:3 and 1:1 ratios of ridge:furrow,
and these were significantly greater than that of flat gravel–sand mulch, without or with irrigation. The
use of ridge with plastic film mulch increased the beneficial effect of RFRHS on yield. The watermelon
yield and WUE for non-plastic-mulched ridge were even lower than that of flat gravel–sand mulch. In
summary, the findings suggest that RFRHS with gravel–sand mulched furrow plus plastic film mulch,
and 1:1 ratio of ridge:furrow, would facilitate the use of limited rainfall most efficiently in improving
watermelon yield, by reducing ET and increasing WUE in this semiarid region.