Objective This study aims to evaluate the effectiveness of a composite practice consisting of a hillside ditch and a daylily (Hemerocallis citrina) vegetative hedgerow in controlling soil erosion and nitrogen and phosphorus losses on sloping cropland in the red soil region of southern China.

Methods Field experiments were conducted on red soil sloping cropland at the Jiangxi Soil and Water Conservation Ecological Science and Technology Park. Treatment plots with the composite practice and untreated control plots were established under a summer peanut (Arachis hypogaea)–winter rapeseed (Brassica napus) rotation system. Runoff and sediment yield characteristics, as well as nitrogen and phosphorus losses, were systematically investigated under different rainfall amounts, rainfall intensities, and fertilization stages.

Results Compared with the control plots, the treatment plots showed significant mitigation effects. 1) Under moderate and heavy rainfall conditions, the average surface runoff depth was reduced by 28.82% and 39.57%, respectively, and the average soil loss was reduced by 46.76% and 73.39%, respectively. 2) Under rainfall intensities of < 1 mm/h, 1–5 mm/h, and > 5 mm/h, the average surface runoff depth decreased by 46.49%, 41.92%, and 11.99%, respectively, while the average soil loss decreased by 30.74%, 69.36%, and 59.47%, respectively. 3) As rainfall amount increased from moderate to heavy, the reduction rate of dissolved nitrogen loss in the treatment plots showed a downward trend, decreasing from 31.01%–39.07% to 21.98%–36.87%, whereas that of dissolved total phosphorus loss increased from 14.73% to 46.57%. As rainfall intensity increased from < 1 mm/h to > 5 mm/h, the reduction rate of dissolved nitrogen loss decreased from 45.02%–57.72% to 8.03%–39.97%, whereas that for soluble phosphorus loss increased from 4.25% to 26.66%. 4) Within 30 days after fertilization, the treatment plots reduced nitrogen and phosphorus losses by 7.42%–32.08%. After 30 days, the reduction rate further increased, reaching a maximum of more than 39%.

Conclusions The composite practice of hillside ditch and daylily vegetative hedgerow effectively reduces runoff and sediment yield, and nitrogen and phosphorus losses on red soil sloping cropland in southern China. These findings provide a scientific basis for the wider promotion and application of this conservation practice.