April 11, 2002

Consider Placing Fertilizer with Seed to Save Time, Boost Crop

With a few precautions, putting down fertilizer with seed can be a spring time saver and boost crop performance, according to a North Dakota State University soil specialist.

"Any fertilizer placed with the seed normally produces some small toxic effects to the seed," says Dave Franzen of the NDSU Extension Service. "But yield boosts due to proximity and convenience for the grower often offset any problems from reduced stands."

There are two basic methods of applying fertilizer with seed, Franzen explains. The first method is to place the fertilizer and seed in separate bands through the use of special seed-boot attachments. The second method is actually placing fertilizer and seed together.

"When you separate fertilizer from the seed in bands, nearly any rate of fertilizer can be applied with little risk of seed germination injury," he says. The exception is when anhydrous ammonia is used. Anhydrous must be placed with at least 3 inches of lateral separation from the seed. With other materials, usually an inch of soil and fertilizer separation in any direction (preferably 2 inches) is enough.

In rows that are wider than 15 inches, applications of urea nitrogen at rates greater than 50 pounds per acre will prevent young roots from entering the fertilizer-rich "hot zone" where they can take advantage of phosphate fertilizer applied in the band. "That cancels out the starter effect of the banded phosphate fertilizer, although that fertilizer is very useful later in the growing season when the crop also has large demands for nutrients," Franzen explains.

Placing seed and fertilizer together is often done using both dry and liquid fertilizers, Franzen says. It cannot be done using anhydrous ammonia, nor is the practice recommended with ammonium thiosulfate. "They are too harmful to seed germination to be applied in the same band as the seed," he says.

However, Franzen reminds that the rate that can be used of seed-placed fertilizers may need to be restricted based on row-spacing, crop, soil texture, and the type of fertilizer materials used. "Also keep in mind that within a given year, environmental conditions, especially soil moisture, play a role in modifying the safety of seed-placed fertilizer," he says. The more moisture in a soil, the more fertilizer can be applied with the seed with little or no adverse effects. Likewise, the more clay in a soil, the more fertilizer can be applied."

Safe rates for applying fertilizer with seed have been established for small grains and are published in two NDSU Extension Circulars- EB-62, "Fertilizer Application with Small Grains at Planting" and SF-712, "Fertilizing Hard Red Spring Wheat, Durum, Winter Wheat, and Rye." EB-62 contains several tables giving a wide range of options for row-spacing, soil texture and soil moisture, while in SF-712 tables are condensed and not as extensive. For canola, circular SF-1122, "Fertilizing Mustard and Canola," contains tables based on Canadian studies for that crop.

The circulars can be obtained from county offices of the NDSU Extension Service or on the Internet at www.ext.nodak.edu/extpubs/soilfert.htm .

Franzen notes that most other crops have restrictions on rates of seed-placed fertilizer. For corn and sunflowers in rows, rates of nitrogen and potash (K2O) should not exceed 10 pounds per acre. For soybeans, no fertilizer for rows exceeding 15 inches, but at narrow rows, up to 10 pounds of nitrogen and potash (K2O) per acre can be used, although broadcast applications may often achieve greater yields.

For flax, dry beans and field peas, no fertilizer should be applied with the seed. Dry bean stands will be adversely affected, and yields of flax and field peas would not be increased with application. Consult the appropriate fertility circular for the crop of interest to learn specifics on seed-placement.

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Source: Dave Franzen, 701-231-8884, dfranzen@ndsuext.nodak.edu
Editor: Tom Jirik, (701) 231-9629, tjirik@ndsuext.nodak.edu