Quantified Benefits of Cultivating Day-Lily (Hemerocallis citrina) Hedgerows over Multiple Years on Sloped Red-Soil Farmland, Southern China

Planting hedgerows is an effective measure for increasing soil and water conservation on sloped farmland, although the comprehensive and dynamic changes in benefits across the life span of the hedgerow are not fully understood. To expand our understanding in this area, day-lily (Hemerocallis citrina) was selected to research the effect of hedgerows built on sloped red-soil farmland in southern China. In situ observations of runoff and soil loss from 2012 to 2018 were recorded in triplicate for two treatments: (1) conventional downslope-ridge tillage (CT) and (2) hedgerow intercropping with downslope-ridge tillage (HT). Micro-topography, soil nutrient content, and crop yield changes in the study plots were recorded. Hedgerows began intercepting runoff and soil loss simultaneously from the second year after they were planted, reducing annual surface runoff (35–66%) and annual erosive sediment (32–87%). As hedgerows became established, they provided increasing positive effects on soil and water conservation. However, those beneficial effects were gradually obscured by changes in micro-topography. The presence of the hedgerow had no obvious influence on soil total nutrient contents under this experimental condition. On average, planting the hedgerow reduced peanut yield by 21% but reduced rapeseed yield only by 2%. Compared with CT treatment, the average economic output of HT treatment after reaching the hedge’s initial production was 1.52 times greater, showing a quadratic trend and reaching a maximum about 4 years after construction by regression. These findings indicate that hedgerow management could be optimized according to the desired beneficial soil and water conservation or crop yield characteristics in different developmental phases.