The optimization of ridge-furrow construction, plant density and fertilizer application are three promising ways to increase rainwater use efficiency, crop yield and water use efficiency. A long-term field experiment was carried out in semi-arid area of northwestern China from 2015 to 2017, using potatoes planted in mini-ditch on ridges with plastic mulching, to explore the effects of fertilizer application and plant density on soil temperature, water consumption at different growth stages, yield and water use efficiency. Two plant densities (low density of 49,500 plants ha -1, and high density of 64,500 plants ha -1) and three fertilization methods (traditional fertilizer application, PM; reduced chemical fertilizer dressing, PMN; and organic fertilizer substitution, PMO) were set up as treatments, using randomized block design with three replications. The high density did not affect soil temperature, SPAD values and yield significantly, but lowered water consumption in pre-flowering stage, above-ground biomass per plant, and water use efficiency. However, LAI and water consumption were improved in post-flowering stage. Compared with low density treatments, LAI in high density increased by 3.64%-15.01%, and water consumption in tuber bulking period increased by 6.50%-48.52%. Both PMN and PMO increased soil temperature in pre-flowering stage, potato foliar SPAD and LAI from squaring to tuber bulking stage, compared with PM. For example, LAI increased by 10.42%-44.26% at flowering stage. PMN and PMO decreased water consumption during pre-flowering period, but increased it during post-flowering period, resulting in a 6.95%-49.85% increment in aboveground biomass at bulking stage. On average, PMN increased potato tuber yield and WUE under low density by 9.96%-20.87% and 13.64%-17.61%, 5.46%-20.81% and 13.25%-45.24%, respectively, compared with PM and PMO. Consequently, the increment of plant density did not affect potato tuber yield and WUE. However, PMN and PMO promoted potato water utilization in post-flowering period and increased LAI, resulting in significant increment of potato tuber yield and WUE, showing an efficient way for fertilization management of potato in semiarid loess plateau of northwestern China.
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