Originally published in Ag News Wire
With only 28 percent of corn acres planted prior to May 9 in Minnesota, growers face the difficult decision of when to begin planting soybeans in order to maintain adequate yields. Soil conditions are of primary importance when considering delayed planting.
Soil conditions and soil temperature
Soil conditions at and after planting usually make a difference in how successfully the crop is established. Soil compaction and smearing is a concern when pulling implements and the planter through, or driving on, wet soil.
To limit soil compaction, keep axle loads under 10 tons and properly maintain air pressure in the tires. Not only does this help the soil, but it will help your tractor run more efficiently and with less slippage. On wet soils, use the lightest tractor that can get the job done.
Soybean has delicate seed, so it benefits when planted about 1 1/2 inches deep, modestly firmed into the seed furrow, covered by relatively loose soil, and into soils with temperatures of 60 to 70 degrees. As of May 9 , soil temperatures at the 2-inch depth averaged 61 and 56 degrees, respectively, at University of Minnesota Research and Outreach centers in Lamberton and Waseca.
The lack of oxygen in saturated soils and the formation of a soil crust of even modest strength can almost eliminate soybean emergence. Therefore, it is important to pay attention to the five-day forecast prior to planting. Planting in cool and wet conditions may lead to poor germination and seedling diseases such as pythium. These problems are magnified by extended cold and rainy periods after planting.
University of Minnesota Extension research indicates that, under ideal conditions, soybeans in southern Minnesota should be planted at about 140,000 live seeds per acre (see Table 1). Soybeans grown in central and northwestern Minnesota require harvest stands of approximately 125,000 to 150,000 plants per acre to maximize yields. This is likely due to shorter-statured soybeans with fewer total nodes that are often produced in these regions. Increased seeding rates are required in central and northwestern Minnesota.
Table 1. Soybean seeding rate recommendations by maturity group.
|Maturity group||Seeding rate|
|Maturity group II soybeans||140,000 live seeds per acre|
|Maturity group I soybeans||150,000 live seeds per acre|
|Maturity group 0 soybeans||160,000 live seeds per acre|
|Maturity group 00 soybeans||170,000 live seeds per acre|
Planting date and soybean yield
Since early-May plantings usually result in maximum yields, lower yields should be expected for later plantings (see Table 2). Planting soybeans in Minnesota on May 10 results in only a 2-percent yield loss; on May 15 in a 3-percent yield loss, and on May 20 in a 6-percent yield loss (or 94 percent of normal yield).
Table 2.Projected yield loss and potential by planting date.
|Planting date||Yield loss (%)||Yield potential (%)|
For more educational information and tools, visit www.soybeans.umn.edu, a cooperative effort among the University of Minnesota, University of Minnesota Extension, and the Minnesota Soybean Research and Promotion Council.