Fertilizer application considerations this spring for 2019
Sandra L.
Wick, Crop Production Agent
Wow, this winter will certainly be one for the history
books! Many producers could not apply
nitrogen (N) fertilizer in the fall due to the persistent saturated soil
conditions, with wet conditions continuing for many soils this spring. As
planting time rapidly approaches, producers may have questions related to the
potential effect of ammonia (NH3) especially for corn seedlings, as well as
soil considerations for anhydrous ammonia applications under suboptimal
conditions. Thanks to Dr. Dorivar Ruiz
Diaz for providing N fertilization information in the latest “KSU Agronomy
Newsletter”, Friday, April 5, 2019 edition.
Starter fertilizer is typically considered as the
placement of a small rate of fertilizer, usually nitrogen (N) and phosphorus
(P), near the seed at planting time. The idea is this fertilizer "jump
starts" growth in the spring, and it is not unusual for a producer to see
an early-season growth response to starter fertilizer application, according to
Dr. Dorivar Ruiz Diaz, K-State Research and Extension soil fertility
specialist. But some producers might
also consider using this opportunity to apply higher rates of fertilizer that
can supply most of the N and P needs for the corn crop. Wet soil conditions in
many areas of Kansas during the fall and winter months continue to limit N
applications for corn. Under these conditions, Ruiz Diaz points out that N
application at planting time can provide a good alternative for some producers.
Producers should be very cautious about applying
starter fertilizer that includes high rates of N (and/or K). It is best to have
some soil separation between the starter fertilizer and the seed. The safest
placement methods for starter fertilizer are either as a deep-band application
2 to 3 inches to the side and 2 to 3 inches below the seed (2x2), or as a
surface-band application to the side of the seed row at planting time (2x0),
especially in conventional tillage or where farmers are using row cleaners or
trash movers in no-till (Figure
1).
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| Figure 1. Graphics by Dr. Dorivar Ruiz Diaz |
What are the risks with “pop-up” placement? Ruiz Diaz
reminds producers if starter fertilizer is applied with the corn seed (“pop-up”
in-furrow), there is an increased risk of seed injury when applying more than 6
to 8 pounds per acre of N and K combined in direct seed contact on a 30-inch
What is a “salt”?
“Salts” are ionic
compounds that result from the neutralization reaction of an acid and base.
Most fertilizers are soluble salts (e.g. KCl from K+ and Cl-). Salt injury can
occur when fertilizer addition increases the osmotic pressure in the soil
solution (due to an increase in salt concentration) around the germinating seed
and roots which can cause plasmolysis (i.e. water moves out of the plant cell,
cell membranes shrink, and the cell collapses). Symptoms of salt damage are
short, discolored roots and a reduced corn population.
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Figure 2. Nitrogen
fertilizer can result in injury from salts, but also from ammonia toxicity when
using urea-containing fertilizers. Urea converts to ammonia, which is very
toxic to seedlings and can significantly reduce final stands Symptoms of
ammonia toxicity from urea-containing fertilizers placed too close to the seed.
Photos by Dr. Dorivar Ruiz Diaz, K-State Research and Extension.
|
What about N rates with 2 X 2 placement or
“surface dribble”? Ruiz Diaz
stresses that starter fertilizer placement, such as 2x2 or surface dribble,
provides enough soil between the fertilizer and the seed and are considered
safe alternatives for higher rates of N application. Recent studies in Kansas suggests that the full rate of N can be
applied safely using these placement options. One concern from some
producers is related to the additional time demands for the application of high
rates of fertilizer during planting. However, this can be an excellent time for
N application, minimizing potential N “tie-up”, and providing available N to
the corn, particularly under no-till systems with heavy residue.
In summary, producers can apply most of the N needs for corn at planting
as long as the fertilizer placement provides enough soil separation between the fertilizer and the seed. The
best options are the 2x2 placement or surface-dribble with similar results in
terms of crop response. Nitrogen applications with the starter fertilizer can
provide an excellent alternative for producers who might not have the
opportunity for anhydrous ammonia applications this spring or are planning to
apply additional N as side-dress.
If you have additional questions on nitrogen fertilization, give Sandra a
call at any of our Post Rock Extension District Offices in Beloit, Lincoln,
Mankato, Osborne or Smith Center.
