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Considerations for Starter Fertilizer in Corn

Source: Dave Nicolai, University of Minnesota Crops Extension Educator

The use of starter fertilizer placement on the seed (known as in-furrow placement) is commonplace in many areas of Minnesota. There are a few things to consider when utilizing starter fertilizer banded on the corn seed. Dr. Dan Kaiser, University of Minnesota Extension Soil Specialist, outlined in a crop news article“Should You Consider In-furrow Starter for Corn” located at Highlights of the article includes the following:

Keep Fertilizer Rates Low. Fertilizer placed in the seed row can have a positive benefit on corn growth early in the growing season and potentially on corn grain yield. High rates of salt and nitrogen products which liberate ammonia (NH30) can have negative effects reducing plant growth and the number of emerged plants. Care should be taken to keep rates low to reduce the risk for damage but maintain a potential for positive benefits from seed placed fertilizer application.

Account for Nutrients in the Starter. The amount of total nutrients applied in the starter should be accounted for in an overall fertility program. While the amount of total nutrients may be low, reducing the amount of a particular nutrient broadcast applied by the rate applied in the starter makes economic sense. Knowing what is being applied by all fertilizer sources in a fertility program helps to keep costs as low as possible and prevent over application of nutrients.

Keep an Eye on Soil Test Values. Many corn producers may be using starter to enhance their broadcast fertility program. In some instances where money may be tight, seed placed fertilizer may be relied on to supply all needed plant nutrients. A low input program will result in a gradual decline in soil test values over the long-term. If soils begin to test low, some broadcast fertilizer may be warranted to increase grain yield and profitability within a given field or field area. Previous knowledge of soil tests will also allow for the reduction of seed placed fertilizer rates in areas where there may be no benefit.

Safe Rates of Seed placed Starter Fertilizer. Excessive concentrations of fertilizer salts near a germinating seed or seedling root causes injury. The injury is caused when the concentration of ions in the soil is greater than the concentration of ions within the plant cells. The high osmotic pressure created by the fertilizer salts causes water to move out of the plant cells and into the soil. As water moves out of the plant cells, the tissue dessicates and becomes blackened; hence the term fertilizer burn. The result is the eventual death of the plant tissue.

In-furrow (pop up or seed row) placed fertilizers are typically applied at low rates but their very close proximity to the seed means that they are more likely to cause injury than 2×2 banded applications because there is little opportunity for the root to grow out of the zone of concentrated fertilizer salts before it dies.

In general to avoid stand loss from fertilizer injury, no more than 10 lb/a of N + K2O should be applied in-furrow regardless of soil texture. The most suitable fertilizers for in-furrow applications will have: 1) low salt index, 2) high water solubility, and 3) no compounds that liberate NH3.


David Nicolai
Extension Educator, Crops & Institute for Ag Prof Coord
(651) 480-7706
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