Subsurface Drain Flow Characteristics During a 15-Year Period in Minnesota

摘要

Two tile drainage research facilities were installed on a Webster clay loam at the University of Minnesota's Southern Research and Outreach Center in southern Minnesota in the mid-1970s. One facility consists of 8 individual tile-drained plots (facility A) with a simulated tile spacing of 27.4 m and the other (facility B) contains 36 individual tile-drained plots with a simulated 15.2 m spacing. Drain flow and nitrate concentration measurements were taken on these plots planted to continuous corn (Zea mays L.) (facility A) and corn and soybean (Glycine max) annually (facility B) from 1987 through 2001. Sixty eight to 71% of the annual drain flow and 71 to 73% of the annual nitrate loss occurred during the 3-month (April-June) period. Drain flow wasgreatly affected by major precipitation events. Greater than 50% of the annual nitrate loss occuired in 10 to 18% of the days drainage occurred. The drainage hydrograph showed flashier characteristics for the 15.2 m spacing compared to the 27.4 m spacing. Results from these two facilities during this 15-yr period have significant implications on: (1) design and approach to drainage research, (2) design and performance of landscape storage structures, including controlled drainage and constructed wetlands, to mitigate nitrate levels in subsurface drainage water (3) fertilizer and manure N management, and (4) the role of subsurface drainage on loss of nitrate to surface waters including the Mississippi River and Gulf of Mexico.