Retention of agricultural surface runoff in a cold-climate vegetative buffer zone – effect of vegetation and season / Vegetasjonssoner i jordbrukslandskapet som rensetiltak for overflateavrenning – Effekt av ulik vegetasjon og årstider
This paper presents an investigation of three vegetative buffer zones (BZ) (10 x 5 m) treating agricultural surface runoff. The experimental full scale BZs were located at Mørdre in south-east Norway. The average retention capacity in BZs (entire experimental period) with only grass and with trees and grass was respectively 33 and 46 % for suspended solids, 34 and 48 % for organic carbon, 23 and 34 % for total P, 28 and 38 % for PO4 3-P, 16 and 31 % for total N, –11 and –2 % for NO3-N and 7 and 28 % for NH4-N. With a few exceptions, there was no difference in retention efficiency (%) between the summer and the winter season. Similarly, there was in general no difference with regard to retention efficiency between the two BZs covered with trees and grass and the BZ covered with grass only. The infiltration capacity in the BZs with trees and grass was not significantly different from the BZ with grass only. Nevertheless, due to better infiltration capacity and increased retention efficiency in the root zone, BZs with trees is recommended. For sedimentation to occur, a dense grass cover is crucial as well, thus sparsely planted trees are recommended.