BMPs for northwestern MN (wheat)

Key points

Best management practices for nitrogen vary region by region. This is because Minnesota has a wide diversity of soils and climatic conditions. As a result, region-specific recommendations have been developed based on the combination of these factors and years of University research.

The northwestern region of Minnesota typically has the least rainfall and evaporation. The soils are predominantly lacustrine, which means they were formed from lake deposits. These soils have clay, clay loam and silty clay loam textures and are poorly drained.

The west-central and southwestern region also has a typically drier climate. With the exception of the far southwestern corner, the soils are predominantly formed from glacial till. These soils generally have clay loam to silty clay loam textures and poor internal drainage.

The typically drier climate of these regions reduces the risk of nitrogen losses. As a result, there are more options available for managing nitrogen.

Recommended nitrogen management practices

Some practices are recommended throughout the state:

• Take credit for nitrogen supplied by previous legume crops, sugarbeet tops and manure.
• Include all sources of fertilizer N:
  • Starter
  • Weed and feed programs
  • Phosphorus sources such as MAP and DAP.

Recommendations specific for wheat in these regions (northwest, west central, and southwest) for fine and medium-textured soils:

Select the optimum N rate for wheat using one of these methods:

• Base the N rate on yield goal, previous crop and soil organic matter (when the soil nitrate test is not used).
• Base the N rate on yield goal and soil nitrate test. Do not use this method when wheat follows a legume.

Recommended N application methods

• Fall application of anhydrous ammonia (AA) when soil temperatures have stabilized below 50 degrees F at a 6-inch soil depth.
• Fall application of urea when soil temperatures have stabilized below 50 degrees F at a 6-inch soil depth.
• Urea should be incorporated to a depth of 3 inches.
• Spring preplant nitrogen application.
• Split applications of nitrogen during growing season.

Acceptable practices with risk

Some nitrogen management practices carry greater risk. These may be either economic or environmental. Economic risk can occur when added inputs don't result in additional yield. Environmental risks are primarily related to potential nitrogen loss to ground or surface waters.

Acceptable practices with risk include:

• Late fall application of ESN.
• Fall application of anhydrous ammonia with a nitrification inhibitor.
• Fall application of urea with either a urease or nitrification inhibitor.
• Spring preplant application of ESN.
• Limit foliar application to 40 pounds N per acre of a liquid source at boot stage or later.

Nitrogen practices that are NOT recommended

Some management practices are not recommended because the economic and environmental risks are too great.

Practices that are NOT recommended:

• Fall application of UAN (28-0-0) or any fertilizer containing nitrate-nitrogen.
• Fall or spring application of urea without incorporation.
• Shallow (2 inches or less) application of anhydrous ammonia (82-0-0) in either fall or spring.
• Application of any N fertilizers on frozen soils. This includes MAP and DAP.