Water Table Level as Influenced by Rainfall, Crop Requirements, and Tiling Method during the past Three Years

In 1979, a portion of the research farm was pattern tiled including the large tillage plots. This was used as an opportunity to compare tile installation methods: a conventional trenching machine (used widely prior to late 70s), and a trenchless “tile plow” machine. The tile plow inserted plastic tile using a mole approach, which is the current primary tiling method. This research showed that plow and trenching tiling methods were not significantly different and both provided adequate drainage. It also showed that water table measurements were influenced more by timing of water needs of the crop being grown and intensity of the rainfall event than tiling method. This report focuses on continued research completed on these trial plots from 2009 to 2011 measuring water table level.

Water Infiltration following Land Rolling of Soybeans

Land rolling of soybean fields has become a popular practice in north central and northwest Iowa during the past five years. Although this technique was first utilized to push rocks into the ground to avoid combine damage and aid in harvesting lodged crops in Canada, producers in Iowa quickly learned that pushing corn root-balls flat at the time of planting and pushing small rocks into the ground can increase harvest efficiency. Typically fields are rolled shortly after planting. One disturbing trend that was noticed, however, was that rolled fields tended to have more water standing between the rows after moderate or heavy rain events. This would imply that water infiltration was slower in fields that had been rolled compared with fields that had not been rolled. Infiltration measurements were taken on a few plots in 2010 at the ISU Northern Research Farm. It seemed that water infiltration was less on the rolled plots. However, we wanted more measurements before publishing any results. In 2011 infiltration measurements were taken on the research farm and on neighboring farms where soybeans had been rolled. The goal was to determine if water infiltration had been reduced by land rolling.

Impact of Liquid Swine Manure Application and Cover Crops on Ground Water Quality

The primary objective of this project was to determine the impact of appropriate rates of swine manure applications to corn and soybeans based on nitrogen and phosphorus requirements of crops, soil phosphorus accumulation, and the potential of nitrate and phosphorus leaching to groundwater. Another purpose of this long-term experimental study was to develop and recommend appropriate manure and nutrient management practices to producers to minimize the water contamination potential and enhance the use of swine manure as inorganic fertilizer. A third component of this study was to determine the potential effects of rye as a cover crop to reduce nitrate loss to shallow ground water.