Methods

Each well consisted of a casing and a pressure transducer. Casings were made of 1.5 diameter PVC pipe. Each casing consisted of a screened interval, approximately 0.61 m in length, and continuous casing from the top of the screened interval to the land surface. Wells were installed via hand augering to greater than 1.5 meters below the water table at the time of installation. Where augering was impeded by subsurface rocks and gravel, steel drive point wells were used. Pea gravel was used to backfill the hole to the top of the screened interval, after which soil removed during the well installation process was re-packed to approximately the same density as prior to installation. A 5 cm layer of bentonite was installed at the land surface to prevent preferential flow down the borehole. After installation, wells were pumped to reduce the risk of fine sediment clogging the well screen, and then Onset HOBO U20 water level loggers were installed in each well. Of the 14 total wells, 9 wells were installed during the 2012 growing season (WIBU-1,2,3,5,7,8,9,10,11) and an additional 5 wells installed during the 2013 growing season (WIBU-4,12,13,14,15). Wells within the field were installed following planting and uninstalled prior to harvest for each growing season; the individual installation and start/end dates are evident in the data. Locations of individual wells are available in the Point Locations dataset. Note that some wells move between years due to uninstallation prior to harvest.

Methods

A gridded set of points distributed at appr. 30 m resolution over the Wibu field site were established during the 2014 growing season. At each of these points, a disturbed soil sample from a depth of 5 cm was collected and used to measure the soil organic content. At a randomly selected subset of these points, an additional undisturbed soil core was collected from a depth of 5-7.5 cm and used to measure porosity, bulk density, and organic content (measured by burning for 24 hrs at 440°C). Undisturbed soil cores were then split into 3 subsamples and a Beckman-Coulter LS-230 laser particle size analyzer was used to measure a continuous particle size distribution. The subsample with the median d50 particle size was used to calculate a variety of soil texture metrics, described in the data table below. These soil texture parameters were used as input to the Rosetta pedotransfer function (Schaap et al., 2001) to estimate soil water retention properties. At each of these points, the 2013 interpolated groundwater metrics and the yield data described in the Yield dataset were extracted using ArcMAP 10.2 software. A full description of this methodology is contained in Zipper et al. (in review).