Abstract: 【Objective】To investigate the effects of reduced basal application of controlled-release fertilizers on watermelon growth and fertilizer use efficiency,providing a reference for the selection,formulation,and water-fertilizer management of watermelon-specific controlled-release fertilizers.【Methods】Using the watermelon variety Qianli No. 4 as the test material,four treatments were established：conventional quick-release fertilizer（T1）,urea-formaldehyde+resin-coated potassium sulfate（T2）,sulfur-coated urea+resin-coated potassium sulfate（T3）,and resin-coated urea+resin-coated potassium sulfate（T4）,with a no-fertilizer control（CK）. The effects of these treatments on dry matter accumulation,nitrogen uptake,potassium uptake,yield,fertilizer use efficiency of watermelon,and soil nutrient contents and enzyme activities were analyzed.【Results】Reduced basal application of controlled-release fertilizers significantly enhanced watermelon dry matter accumulation. At the fruit expanding stage,T4 treatment resulted in a dry matter accumulation of 276.8 g/plant,representing increases of 24.7% and 75.0% compared to T1 treatment and CK,respectively. Nitrogen and potassium uptake under T4 treatment at the same stage were 6.0 and 6.9 g/plant,respectively,showing increases of 40.8% and 54.7% compared to T1 treatment. Yield under T4 treatment was 27.2% higher than T1 treatment,and nitrogen and potassium use efficiencies were improved by 265.9% and 139.2%,respectively. Regarding soil quality,no significant differences in available phosphorus content were observed among fertilizer treatments（P>0.05）. However,T4 treatment significantly increased soil organic matter,available nitrogen,and available potassium contents by 27.1%,30.8%,and 46.9%,respectively,compared to T1 treatment（P<0.05）. Soil sucrase and catalase activities showed no significant differences among the four fertilizer treatments（P>0.05） but were significantly higher than CK（P<0.05）. Soil urease activity in T2 treatment and CK was lower than in other treatments.【Conclusion】Reduced basal application of controlled-release fertilizers have positive effects on watermelon growth,yield,fertilizer use efficiency,and soil quality. The combination of resin-coated urea+resin-coated potassium sulfate（T4） demonstrate superior fertilizer efficacy and soil improvement effects.

Key words: Watermelon, Controlled-release fertilizer, Reduced basal application, Growth, Yield, Fertilizer use efficiency, Soil quality