Evaluation of Foliar Manganese Applications in Glyphosate
To determine if the addition of Manganese in with foliar postemerge applications of glyphosate
herbicides in glyphosate tolerant soybeans will provide a yield benefit.
Soil Type: Hoytville silty clay loam, Herbicide:
Hoytville clay BURNDOWN: 12 oz./A Domain + 1 qt./A
Drainage: Tile- nonsystematic (April 26) Touchdown + 1 pt./A 2,4-D
Previous Crop: Corn LVE + 17 lb./100 gal. AMS
Tillage: No-till POST(June 25): 22 oz./A Roundup WeatherMax
Soil Test (2002): pH 6.4, P 48ppm, K 135ppm + 17 lb./100 gal. AMS
Fertilizer: 185 lb./A 0-0-60 surface Variety: Wellman W3228RR
broadcast (October 2002) Planting Rate: 210,000 seeds/A (7.5 inch row
Planting Date: May 23, 2003
Harvest Date: October 1, 2003
This study consisted of three treatments replicated four times in a complete randomized block
design. The treatments were 1 qt./A Postman 5% manganese, 2 qt./A Postman 5% manganese,
and an untreated check. The manganese treatments were added to a postemerge foliar
glyphosate application on June 25 when the soybean plants were at growth stage V2-V3.
Applications were made with a Great Plains ground sprayer in 15 gallons per acre spray volume.
Plot size was 45 feet wide by 1,090 feet long. Harvest populations (September 26) were
estimated by counting the number of plants in the row on each side of a 10 foot section at three
different locations in each plot. The average number of plants counted per 10 feet was converted
to plants per acre. Yields were determined by harvesting one round (28 feet) out of the center of
each plot with a John Deere 6620 combine equipped with a calibrated AgLeader PF3000 yield
monitor. Plot weights were measured with a calibrated weigh wagon and moistures were taken
from the combine yield monitor. All yields were adjusted to a 13% moisture standard.
Table 1. Soybean harvest population, moisture, and yield means for each treatment.
Treatment Harvest Population Moisture Yield
(plants/A) (%) (bu./A)
Untreated Check 158,600 13.1 56.0
1 qt./A Manganese (5%) 157,400 12.9 55.4
2 qt./A Manganese (5%) 158,300 13.0 55.9
LSD (P=0.05) NS NS NS
F-test <1 1.7 1.2
CV (%) 7.6 1.3 1.2
NS= not significant
Results of this one year study indicate no statistical differences in harvest population, moisture,
or yield from the addition of manganese in a foliar application. Although manganese is the most
common micronutrient deficiency found in Ohio soybeans, it generally occurs in fields with
higher pH levels and higher organic matter which can reduce its availability to the plant. It is
also more likely to occur in cooler weather. Consideration should be given to these factors when
determining when and where to use a manganese supplement. Common symptoms of
manganese deficiency are stunted plants, and yellow to whitish leaves with the veins remaining
This test field had not previously shown any symptoms of manganese deficiency. However
some agribusinesses and farmers are adding manganese to postemerge herbicide applications as a
preventative measure. The additional cost for adding the Postman manganese supplements in
this trial was $1.94 for the 1 qt./A rate and $3.88 for the 2 qt./A rate based on in season pricing
with no discounts.
Reductions in weed control have been reported when some manganese products are tank mixed
with certain herbicides. For this reason, it is important to determine if the manganese product
being considered has been tested and is compatible with the particular herbicide to be used, and
that proper mixing instructions for the specific products being used are followed. Previous
testing conducted by Monsanto indicated no antagonism exists between Postman and Roundup
WeatherMax used in this study.
The authors express appreciation to Royster Clark of Delphos for supplying the Postman
(Traylor Chemical Company) used in this study.
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Keith L. Smith, Associate Vice President for Ag. Administration and Director, OSU Extension.
TDD No. 800-589-8292 (Ohio only) or 614-292-1868