Multispecies riparian buffers trap sediment and nutrients during rainfall simulations

A study was conducted to evaluate the ability of a multispecies riparian bu ffer (MRB) to remove sediment, nitrogen, and phosphorus from cropland runof f. Simuiated rainfall was applied to 4.1- by 22.1-m bare cropland source ar eas paired with either no buffer, a 7.1-m-wide switchgrass (Panicum virgatu m L. cv, Cave-n-Rock) buffer, or a 16.3-m-wide switchgrass-woody plant buff er. Each treatment plot combination had three replicates. The switchgrass b uffer trapped 70% of the incoming sediment, while the switchgrass-woody buf fer trapped more than 92%, In general, these buffers retained 93% of sand a nd silt particles and 52% of clay particles. During a 2-h rainfall simulati on at 25 mm h(-1), the switchgrass buffer removed 64 61, 72, and 44% of the incoming total N, NO3-N, total P, and PO4-P, respectively. The switch gras s-woody buffer removed 80, 92, 93, and 85% of the incoming total N, NO3-N, total P, and PO4-P, respectively. During a I-h rainfall simulation at 69 mm h(-1), the switchgrass buffer removed 50, 41, 46, and 28% of the incoming total N, NO3-N, total P, and PO4-P. respectively, The switchgrass-woody pla nt buffer removed 73, 68, 81, and 35% of the incoming total N, NO3-N, total P, and PO4-P, respectively. The switchgrass buffer was effective in trappi ng coarse sediment and sediment-bound nutrients. But the additional buffer width with high infiltration capacity provided by the deep-rooted woody pla nt zone was effective in trapping the clay and soluble nutrients.