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Without question, there is increasing interest among corn growers in various options that might be used to place fertilizer near corn seed at planting. This interest is driven by several factors including: 1) earlier planting, 2) higher fertilizer prices and the desire to be more efficient, 3) use of larger planters where 2x2 attachments do not fit, 4) many fields having medium or higher soil test values, and 5) a desire to have a positive impact on the environment.

There are several options for placing fertilizer near the seed. Most work best with fluid fertilizers. With inexpensive attachments, corn planters can be modified to place fertilizer with, below, or above the seed. These placements substitute for the more traditional 2x2 placement that usually requires the use of a double disc opener.

Obviously, the replacement of the 2x2 placement option raises questions about the effectiveness of other methods of placing fertilizer close to the seed. There is also concern for germination damage when new placement options are considered.

In order to gather some needed information about placement of fertilizer close to the seed, a study was conducted near Winthrop in Sibley County in 2004. For this study, three fluid fertilizers (10-34-0, 4-10-10, 3-18-18) were applied at two rates. The 10-34-0 and 4-10-10 were each applied at 5 and 10 gallons per acre. To equalize the rate of K₂O applied in the 4-10-10, the rates of 3-18-18 were decreased to 3.4 and 6.8 gallons per acre.

A John Deere planter was fitted with a Rebounder attachment to place the fertilizer in three positions close to the seed. These were: 1) in contact with the seed, 2) in a dual band above the seed, and 3) in a single band above the seed. An appropriate control (no fertilizer near the seed) was also used.

A field having very high soil test values for P and K was selected. Adequate N was applied by the cooperating farmer. Corn was planted on April 27.

Corn emergence was measured at about four weeks after emergence by counting the number of plants in 20 feet of row. Grain yields were hand harvested when grain moisture was about 25%.

The effect of treatment on emergence for this soil having a silty clay loam texture is summarized in the following table. The numbers are reported as a percent of the control (no fertilizer applied).

Corn emergence as affected by rate and placement of three fluid fertilizers near the seed.

control emerged population = 33,320 plants/acre

There were small differences among treatments. In several situations, the treatment used enhanced emergence slightly. For several years, enhanced emergence has been one of the reported benefits for using banded fertilizer near the see. The emergence values reported in the previous table confirm this benefit.

There was a slight reduction in emergence when the 10-34-0 was applied at a rate of 10 gallons per acre in contact with the seed. Several growers have used this product at a rate of 8 gallons per acre or less and have not reported any problems with emergence. The results from this study suggest that rates of 10-34-0 as high as 10 gallons per acre should not be used. The high rate of 10-34-0 would supply about 12 lb. N per acre. This rate of N applied in contact with the seed is capable of causing problems with emergence and lower rates of N should be used.

Even though the summer was cool, grain yields were excellent. These yields are summarized in the following table.

Corn yields as affected by rate and placement of three fluid fertilizers near the seed.

yield of control = 213.3 bu./acre

There was some variability in yields. This variability, however, was attributed to yield variability in the field and was not the result of the treatment that was used. With soil test values for P and K being very high (63 ppm and 215 ppm respectively) a yield increase from banded fertilizer was not expected and none was measured. Even though the 10-34-0 placed in contact with the seed at a rate of 10 gallons per acre caused a slight reduction in emerged stand this reduction was not reflected in yield. None of the other treatments used had a statistically significant negative effect on yield.

The results of this study show that there are several options that can be used to place fluid fertilizer in a band near the seed without causing a negative impact on either emergence or yield. One placement did not appear to be superior compared to the others. A placement which allows for some soil between seed and fertilizer would reduce any risks associated with placement of banded fertilizer near the seed.

There are some cautions to be aware of when thinking about placing fertilizer close to the seed. Use of ammonium thiosulfate (12-0-0-26) in contact with the seed should be avoided. This fluid fertilizer contains free ammonia which, when in contact with the seed, can reduce emergence. If this product is used, these should be one inch of soil between seed and fertilizer. Reduced emergence is also the end result for contact of urea with corn seed. So, fertilizer containing nitrogen supplied from urea should not be placed in contact with corn seed.

Boron fertilizers also have a negative on emergence. There are no known situations in Minnesota where this nutrient is needed for corn production. Nevertheless, for those who think that they should use this micronutrient, it should not be applied in contact with corn seeds.