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Title: WATER TABLE LEVEL AS INFLUENCED BY TILING METHOD

Author
item Colvin, Thomas
item Cook, Jeffery - Jeff
item PECINOVSKY, KEN - IA STATE UNIVERSITY

Submitted to: Iowa State University Northeast Research and Demonstration Farm 2003 Report
Publication Type: Popular Publication
Publication Acceptance Date: 1/29/2003
Publication Date: 2/15/2003
Citation: Colvin, T.S., Cook, J.D., Pecinovsky, K. Water table level as influenced by tiling method. Iowa State University Northeast Research and Demonstration Farm 2002 Report. Available: http://www.ag.iastate.edu/farms/02reports/ne/watertablelevel.pdf.

Interpretive Summary:

Technical Abstract: Sections of the research farm were tiled in the fall of 1979. The primary reason for the tiling was to provide a good soil environment for large tillage trial plots that had been previously established. This was also used as an opportunity to install a comparison of tile installation with a conventional (at that time) trenching machine and a relatively new system of installing the tile with a "tile plow" machine. The tile plow inserted plastic tile using a mole approach, which opened the soil and inserted the tile without leaving an open trench, which later required backfilling. The heaving of the soil by the tile plow did require packing and some soil manipulation to allow cropping. The primary reason for using this type of installation was cost. At the time of this installation, the cost of tiling could be reduced substantially (in some cases over 50%) by using the plow method rather than the trench. Four-inch plastic subsurface drain tile was professionally installed in blocks of three by contractor machines so that the water table depth could be measured at intervals from the middle tile with similar installation methods on each side. Ground water table depth observation wells were installed and records of the depths to water table have been maintained through 2002. It is generally believed that when the water table is at least 12 in. below the surface, it does not generally interfere with machine traffic or plant growth. Using that as criterion, there are very few times in the five years when the water table depth is less than 12 in. from the surface. Notable times with shallow water tables are three times for 1999 (early April, late May, and early June) and one time in early May for 2001. Generally speaking, the plow method tends to have somewhat higher water tables than the trench, but it appears that any extra cost for the trench may not be justified by the performance difference. There were times in both 1998 and 2000 when the methods differed markedly from each other with each method showing a shallower water table in one year. This is probably due to crop rotation differences above the lines.