Fertilizer use is a key management practice
for growers who seek to get maximum profit from their soybean
acres. While major attention is devoted to fertilizer use for
the corn, the soybean crop is frequently overlooked. The information
in the following table shows that phosphate fertilization,
for example, can be profitable if soil test values for phosphorus
are in the low or very low category.
Return on dollars invested in P fertilization of soybeans in
Minnesota
| P2O5 Applied |
Yield |
Yield Increase |
Gross* Return |
Net** Return |
$Return ÷ $Invested |
| lb/acre |
bu/acre |
bu/acre |
$/acre |
$/acre |
$ |
| 0 |
44.0 |
--- |
--- |
--- |
--- |
| 23 |
46.7 |
2.7 |
10.80 |
5.05 |
1.88 |
| 46 |
54.2 |
10.2 |
40.80 |
29.30 |
3.55 |
| 69 |
55.7 |
11.7 |
46.80 |
29.55 |
2.71 |
| 92 |
55.9 |
11.9 |
47.60 |
24.60 |
2.07 |
*assumes a value of $4.00/bu
**assumes a price of $0.25/lb P2O5
The results from this study show that the rate of phosphate
that produces the highest yield is not necessarily the same as
the rate that produces optimum return for dollar invested in
phosphate fertilizer. Nevertheless, phosphate fertilization is
profitable if the soil test for phosphorus is low as it was in
this situation.
The University of Minnesota recommendations for phosphate use
for soybeans have been revised from those used in the past. These
recommendations are summarized in the following table.
Phosphorus fertilizer for soybean production in Minnesota
| Expected Yield |
Phosphorus (P) Soil Tests, PPM |
| Bray |
0-5 |
6-10 |
11-15 |
16-20 |
21+ |
| Olsen |
0-3 |
4-7 |
8-11 |
12-15 |
16+ |
| bu/acre |
- - - - - - - P2O5 to apply
(lb/acre) - - - - - - - |
| Less than 30 |
|
50 |
30 |
0 |
0 |
0 |
| 30-39 |
|
60 |
40 |
0 |
0 |
0 |
| 40-49 |
|
70 |
50 |
0 |
0 |
0 |
| 50-59 |
|
80 |
60 |
0 |
0 |
0 |
| 60+ |
|
90 |
70 |
0 |
0 |
0 |
The information in this table shows that
it's important to know the soil test value for phosphorus. Research
has shown that response to phosphate fertilization should not
be expected if the soil test for P is higher than 10 ppm (measured
by the Bray procedure) or 7 ppm (measured by the Olsen procedure).
As with phosphate use, the soybean crop will also respond to
the application of potash.A grower should not expect a response
to potash fertilization if the soil test for potassium is higher
than 120 ppm.Potash fertilizer suggestions are listed in the
following table.
Potash fertilizer suggestions for soybean production in Minnesota
| |
Potassium (K) Soil Test, PPM |
| Expected Yield |
0-40 |
41-80 |
81-120 |
121-160 |
161+ |
| bu/acre |
- - - - - - - K2O to apply (lb/acre) - - -
- - - - |
| Less than 30 |
55 |
30 |
15 |
0 |
0 |
| 30-39 |
65 |
40 |
20 |
0 |
0 |
| 40-49 |
80 |
50 |
20 |
0 |
0 |
| 50-59 |
100 |
60 |
30 |
0 |
0 |
| 60+ |
110 |
70 |
30 |
0 |
0 |
Placement of phosphate and potash fertilizers
is an important consideration for soybean production. Several
studies in the northern and western Corn Belt have shown broadcast
applications being superior to banded use.
Plans for fertilizing the soybean crops should focus on a spring
application. With this timing, fertilizer is applied near the
time of use or uptake. There is less time for contact between
the fertilizer and the soil producing more efficient use of the
applied fertilizer.
Fertilizer management for the soybean crop should not be complicated. With
the focus on appropriate use of phosphate and potash fertilizer,
developing a fertilizer program for soybean production is easy
and can be very profitable. |
