Minnesota
crop producers working for the extra yield have frequently
considered the use of foliar application of fertilizer for
both crops. Is this practice important? Does it pay? These
are two of the frequently asked questions.
The concept
of foliar fertilization has been researched for several years.
Several projects focused on this management practice during
the mid-1970’s. More recently, there has been an intensive
evaluation of in-season application of fertilizer – N
for soybean production. Results of some of the research trials
conducted in Minnesota are summarized in the tables that
follow.
Application
of fluid fertilizer containing N, P2O5, K2O, and S was evaluated
for corn production at the Southern Research and Outreach
Center at Waseca. This mixture was applied 1, 2, or 3 times
from mid-August through early September. Nutrients applied
with each time of application were 25.3, 12.5, 6.3, and 1.0
lb of N, P2O5, K2O and S respectively. The results are listed
in Table 1. All treatments received full N at 150 lb./acre
as 82-0-0. In addition, there was a broadcast application
of 60 lb. P2O5 and 100 lb. K2O per acre.
Table
1. Corn yield as affected by foliar application of N, P2O5,
K2O and S.
Time
of Application
of Fluid Fertilizer |
Yield |
| |
(bu/a) |
| none |
131.2 |
| 8/13 |
135.9 |
| 8/13,
8/20 |
125.4 |
| 8/13,
8/20, 9/1 |
133.9 |
The application
times were selected so that the fluid fertilizer would be
applied during grain fill. The results of this study showed
that foliar application of fertilizer had no positive effect
on corn yield.
Following
a report of a positive response of foliar application for
a soybean crop, trials were conducted at three locations
to evaluate the potential use of this management practice
for soybean production in Minnesota. The fertilizer was applied
during pod fill. The results are summarized in Table 2. There
were two varieties at each location. Results were consistent
with both varieties. Values in Table 2 are averages for the
two varieties.
Table
2. Influence of foliar application of fertilizer on soybean
yield.
| Nutrient
Applied |
Location |
| N |
P2O5 |
K2O |
S |
Waseca |
Becker |
Rosemount |
| lb/acre |
bu/acre |
| 0 |
0 |
0 |
0 |
57 |
53 |
59 |
| 40 |
4 |
12 |
3 |
56 |
54 |
57 |
| 80 |
8 |
24 |
6 |
59 |
50 |
59 |
| 80 |
8 |
24 |
6+micros |
54 |
45 |
56
|
These results
show that foliar fertilization is not a management practice
that will increase soybean yield. Other universities throughout
the Corn Belt conducted similar studies. The results were
similar. Foliar fertilization had no effect on soybean yield.
There is
a risk to foliar fertilization. The N could cause burning
of the foliage and reduce yield. The yields summarized in
Table 3 illustrate this risk. The N was applied as liquid
urea to supply 75 lb. N per acre.
Table
3. The effect of application of fertilizer N (urea) on
soybean yield.
| Treatment |
Yield |
| |
(bu/a) |
| control
(no N) |
45.1 |
| liquid
urea (early bloom) |
42.4 |
| liquid
urea (late bloom) |
37.6 |
In this
study, the yield reduction from the late application of urea
was caused by foliage burn.
Studies
with in-season application of fertilizer N have been more
extensive. In these trials conducted throughout Minnesota
at 15 sites, there was a positive response to N at one site.
While the
foliar application of fertilizer may seem like a logical
management practice, this method of fertilizer application
has not increased yield of corn and soybean in Minnesota.
This practice is not recommended.
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