The effect of supplemental irrigation on watermelon (Citrullus lanatus) production in gravel and sand mulched fields in the Loess Plateau of northwest China

Trials were conducted to examine the effects and economic feasibility of supplemental drip irrigation on watermelon (Citrullus lanatus) production in fields with and without surface mulch consisting of a mixture of gravel and sand in the Loess Plateau of northwest China in 2001 and 2002.The trial involved four levels of drip irrigation: 0, 23, 45 and 68 mm of water to both mulched and non-mulched fields (control). Both treatments were randomized with four replications. There was a significant difference in rainfall amounts between the two experimental years. Rainfall during the watermelon growth period was 126 mm in 2001 and 223 mm in 2002. In 2001, 45 mm of irrigation increased yields by about 36% and 68 mm increased yields by about 46%. Drip-irrigation, with 68 mm had the highest water use efficiency (WUE), 24.7 kg m−3, which was 29.3% more than the non-irrigated treatments. In the wet year, 2002, supplemental irrigation decreased WUE for the mulched fields but did not significantly increase yields. However it did increase yields in the non-mulched fields: 23, 45, and 68 mm of irrigation increased yields by 21, 26 and 38%, respectively.