Issue 18
January
1999 		Air seeder placement of wheat seed, fertilizer focus of study

By Tracy Sayler
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Prairie Grains is the official publication of
the Minnesota
Association of
Wheat Growers,
North Dakota Grain Growers Association,
South Dakota Wheat, Inc., and the Minnesota Barley Growers Association.

 Air-seeder technology provides the opportunity of delivering wheat seed and fertilizer to the soil in several seed-fertilizer placement options in a single pass across the field. But two major questions have arisen as growers have adopted this technology: What impact will placement of nitrogen with or near the seed have on production? And are standard phosphorus recommendations adequate for air-seeder seed-fertilizer placement strategies?

These questions are being researched at the University of Minnesota, in a study funded in part by the Minnesota wheat checkoff, administered by the Minnesota Wheat Research and Promotion Council. Albert Sims at the Northwest Experiment Station in Crookston, MN, and George Rehm, UM soil scientist in St. Paul, are conducting the study, in its second year in 1998.

Growers have reported applying up to high amounts of fertilizer with seed using airseeders with no detrimental effects on plant stands. For example, anhydrous ammonia is often placed about two inches on either side of a wide seed band. However, this study suggests seedling emergence will be reduced as higher rates of fertilizer, especially N, are applied with the seed. This study used four N rates (0, 25, 50, 75 lbs N) and five P rates (0, 23, 46, 69, 92 lbs P).

Broad band mixtures (seed and fertilizer mixed with sweeps in a three-inch wide band) resulted in generally the highest overall yields, especially at three of the four N rates applied at planting. Narrow band mixes tended to decrease grain yield with increasing N rates.

Wheat has the capacity to compensate for reduced plant stands with increased tillering. Results of this study indicate that less seedling emergence in a broad band mix was compensated for with increased tillering that produced grain. Not so with the narrow band mix, however.

The study indicated a reduction in seedling emergence with high rates of P mixed with the seed, but this may have been due to the increased N applied with the P fertilizer source (18-46-0).

Soil conditions, soil texture and soil moisture can determine seed-fertilizer placement effects on germination, seedling injury, and grain yields, the researchers say. Fine textured soils in moist conditions generally result in less detrimental effects from high fertilizer rates in contact with the seed than coarse textured soils in dry conditions. This fact may help guide seed-fertilizer placement decisions at planting.

For more details on this research project and others funded by the Minnesota wheat checkoff, request the booklet "1998 Wheat Research Review" from the MWRPC, phone 1-800-242-6118.
Copyright Prairie
Grains Magazine
January 1999