Crop & Pest Report

Accessibility


| Share

Updated Soybean Fertility Recommendations (05/07/20)

The NDSU soybean fertility recommendations were updated this winter based on research conducted by NDSU researchers at Minot, Dickinson, Carrington and Fargo during the past decade.

The NDSU soybean fertility recommendations were updated this winter based on research conducted by NDSU researchers at Minot, Dickinson, Carrington and Fargo during the past decade. These recommendations can be accessed at https://www.ag.ndsu.edu/publications/crops/soybean-soil-fertility . The major changes are:

Inoculation - Inoculation any time does not hurt soybean agronomically; however, given the economic conditions it would rarely provide a positive return to a grower who has planted soybean in the same field within the past 4 years. If a field is in soybean for the first time, double inoculation is key to success (peat or liquid combined with a granular inoculant application).

N - There is no need for any N with soybean at any time.

P - The critical value for the Olson soil test has been reduced to 8 ppm. At 8 ppm or higher, no P would be needed. P fertilizer can be applied, but do not expect an economic return. No fertilizer (other than an appropriate iron (Fe) fertilizer with water) should be applied to the seed, or stand reduction and yield reduction would be the probable result. Mid-row banding of P is not effective. Side-banding or broadcast P is the method for applying P to soybean.

K - The rate depends on the smectite/illite ratio of the soil (see map in circular) and the K soil test. Cation balance is not a factor.

Soil pH - No lime is necessary if the surface pH is 5.7 or greater. In long-term no-till fields, sampling by zone and with a 0-2 inch and 2-6 inch depth will better define areas where liming might be needed. In western no-till areas, more soils with pH less than 5 are being found and these should be surface limed.

Iron (Fe) - There are several new formulations of Fe fertilizers being tested, but for now, Fe ortho-ortho-EDDHA is by far the best Fe fertilizer. Its use should be in-furrow at seeding, using rates recommended on the label. Iron deficiency chlorosis in eastern ND can be minimized by:

  1. Selecting a field without excessive carbonates/salts.
  2. Selecting a very tolerant variety based on NDSU test results.
  3. Increase plant population.
  4. Use a companion cover crop (barley or oats) at seeding.
  5. Fe-o-o-EDDHA in furrow.

 Sulfur - Soybean is not as susceptible to S deficiency compared with corn or small grains or canola. It is possible to have S deficiency on upland field positions in deep sandy soils in years with excessive fall/winter/spring precipitation (this year?). The soil test is not diagnostic for S sufficiency or deficiency.

Foliar fertilizer - Use of foliar fertilizer to increase soybean yield in ND has not been effective.

 

Dave Franzen

Extension Soil Specialist

701-799-2565

This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

USDA logo

Creative Commons License
Feel free to use and share this content, but please do so under the conditions of our Creative Commons license and our Rules for Use. Thanks.