Determining optimum management strategies for high yielding corn and soybeans while optimizing profit and minimizing environmental risks are priorities of crop and livestock producers in Minnesota. This long-term research project is an on-going collaboration involving farmers, scientists from the University of Minnesota and the USDA Agricultural Research Service, Extension specialists, and the Minnesota Department of Agriculture.
Long-term research allows questions to be addressed against a wide range of climatic conditions; allows for the inclusion of episodic events such as floods, droughts, and pest and pathogen outbreaks; allows for the detection of important but slow-acting phenomena such as changes in soil physical, chemical and biological properties; and also allows for diverse collaborations to form.
The maximum drainage intensity provided by conventional subsurface drainage systems is not usually needed at all times during the growing season, so there is opportunity to reduce drainage intensity during some periods without compromising the objectives of the drainage system using controlled drainage.
By inserting or removing weir-boards in strategically placed water control structures, the threshold outlet elevation of a drainage system can be raised or lowered to adjust the outlet water level elevation and thereby change drainage intensity. When the threshold outlet elevation is below the outlets for the lateral drains, the system operates in conventional drainage mode. In controlled drainage mode, when the weirs are raised to an elevation above the outlets of the laterals, drainage from the system will not occur until the water level in the outlet rises above the weir-board threshold outlet elevation. Drainage intensity is reduced and water is conserved in the soil profile. During the non-growing season the weir-boards are raised to within six inches of the soil surface to conserve water and nutrients, while during the growing season they are generally positioned about 24 inches below the soil surface to conserve water and nutrients for crop use. When field operations such as planting or harvest are necessary all of the weir-boards are removed to ensure trafficable conditions.
The objectives of this long-term, field-scale experiment include:
Subsurface tile drainage was installed on a 91 acre site (Field B) and a 50 acre site (Field G) near Tracy, MN, Redwood County during fall 2005 and fall 2009, respectively. Field B was divided into two management zones and Field G was divided into four management zones (Table 1). Each zone outlets into a manually operated water level control structure. Water table depth is managed to test the effect of water table management on crop performance, drain flow volume, and nitrogen and phosphorus loss. Field B has been monitored since 2006 for soil and plant nutrient status at 48 georeferenced locations, grain yield by combine yield monitor, and water quality measurements. Field G has been monitored since 2006 for soil and plant nutrient status at 24 georeferenced locations and grain yield by combine yield monitor. Field G has been monitored for water quality measurements since 2009.
View tables (.pdf)
Soil and Water Outreach