Effect of Field Margin Management and Slope on Sediment Trapping during the Monsoon Season in South Korea.

An important role of field margins in agroecosystems is to reduce or prevent soil erosion. The aim of this study was to quantify the effect of two contrasting field margin management options, i.e. "managed" and "natural", on the potential of field margins to trap sediment, in margins with either shallow or steep slopes.

Fifteen Astroturf mats (34 cm by 25 cm) were installed at twelve sites in Haean catchment, South Korea, arranged in three levels before, within, and after the field margin, with five mats at each level. All sites had radish crops on the upslope field. The total of 180 mats were installed in May 2013 and monitored regularly after each rain event until the end of the monsoon season.

Preliminary results confirm the expected positive relation between rainfall amount and sediment deposition. There was a little difference in the amount of trapped sediment before field margins in the four cases (18.54 ± 0.29 g/cm² in natural/flat, 18.52 ± 0.55 g/cm² in natural/steep, 18.70 ± 0.72 g/cm² in managed/flat, 17.40 ± 0.40 g/cm² in managed/steep).

In natural field margins, most of the sediment was trapped within the field margin (20.15 ± 1.31 g/cm² and 24.05 ± 0.81 g/cm² for flat and steep slopes, respectively); after the field margin, only 11.75 ± 1.00 g/cm² and 12.76 ± 0.88 g/cm² were trapped. In contrast, in managed field margins, most of the sediment was only trapped after the field margin (20.50 ± 1.81 g/cm² and 22.31 ± 1.08 g/cm² for flat and steep slopes, respectively). Within managed field margins, more sediment was trapped in shallow (19.46 ± 1.15 g/cm²) than in steep slopes (11.44 ± 0.90 g/cm²).

In a next step we will incorporate soil and vegetation data into the analysis for a broader picture on the effect of management and slope on sediment trapping in field margins.