Starter Fertilizers in Corn
What is starter fertilizer?
Key Points
 Starter fertilizer is a small amount
of fertilizer placed close to the
seed at planting to help enhance
seedling growth and
development.
 Uniform crop establishment and
early vigor are ideal and important
during early growth stages and
can potentially impact plant
development and yield.
 When choosing a starter fertilizer
system, consider the nutrients
available/supplied by the material
used, application rate, and
placement options available.
A relatively small amount of fertilizer placed in close proximity to seed at or around planting to
help enhance the growth and development of emerging seedlings is considered starter fertilizer. It
is used to provide easily accessible nutrients to developing plants until they establish larger root
systems. To be considered starter, fertilizer must be placed in such a manner as to enhance early
seedling vigor and development, usually directly below or to the side of the seed. Starter is usually
composed of nitrogen (N) and phosphorus (P). The N in starter fertilizer can help prevent early N
deficiency when cold soil conditions slow the release of nitrogen from organic matter and P is
important for promoting vigorous root growth needed for healthy, dark green plants.
Why use starter fertilizer?
Corn plant roots develop in two distinct phases, seminal and nodal roots. Seminal roots gather
moisture from the soil while young seedlings use up the food reserves from the kernel. Once
plants emerge from the soil, the nodal root system begins to develop which will become the
primary route for water and nutrient uptake in the plant. During corn growth stages V1 through
V5, preventing stress to the developing nodal root system is crucial because stunting during
nodal root system development can stunt the entire plant’s development and thus yield potential.
Around stage V3, corn plants transition from dependence on kernel reserves to nodal root uptake
(Figure 1). The success of this transition can be the key to a healthy, uniform crop. This is where
starter fertilizer comes into play.
Starter fertilizer acts to provide nutrients in close proximity to immature root systems that do not
yet have the size and bulk density to access necessary nutrients from the soil, especially under
less than ideal soil conditions. Specific planting circumstances that may benefit from the use of
starter fertilizer include:
 Soils that have tested low in P
 Cool soil temperatures associated with early planting
 High residue cover associated with conservation tillage situations
 Northern Corn Belt locations
 Coarse textured (sandy) soils low in organic matter
 Poorly drained fields
 Soils either high or low in pH
 Locations where substantial drought stress is likely
Uniform crop establishment and early vigor are ideal and important during early growth stages and
can potentially impact plant development and yield. Not only are healthy, fast-growing young
seedlings better able to compete with weeds, but they can also be more resistant to insects and
diseases. Early rapid growth also helps to hasten the onset of large leaf formation which is
necessary for photosynthesis.
Considerations for using starter fertilizer.
Figure 1. Corn plant at growth stage V3, the period
of transition from kernel reserves to nodal root
uptake. Starter fertilizer helps to ensure the success
of this transition.
When choosing a starter fertilizer system that works best for your specific field or operation, there are three main things to consider: the nutrients
available/supplied by the material used, application rate, and placement options available.
Materials. When using a starter fertilizer that contains both N and P, optimum results can be obtained when combining phosphate with ammonium
nitrogen. Monoammonium phosphate (MAP – 11-52-0) or ammonium polyphosphate (10-34-0) (liquid) based fertilizers are excellent choices.
Nitrogen in ammonium form can help to enhance the use of P in the starter as well as P uptake from soil. Generally,
starters should contain a high phosphate (P2O5) ratio and the phosphate should be highly water soluble. A fertilizer does
Channel.com
For additional agronomic information, please contact your Channel Seedsman
Starter Fertilizers in Corn
not have to be labeled “starter” to be used as such if it meets the needs for your situation
and follows basic defined parameters of rate and placement. Depending on soil test results,
micronutrients can also be provided in formulation to meet specific needs. Starter fertilizers
can be applied in both solid and liquid forms as generally there is no difference in
effectiveness. Liquid fertilizers may be more expensive than dry formulations, but when
properly applied can require lower quantities and still be cost effective.
When a field has tested high in P, such as those on farms where manure is applied, there
are a few options to gain effective starter response from fertilizer without adding significant
amounts of P to already high testing soil. One option is the use of N only fertilizers such as
ammonium sulfate (21-0-0-24S) or ammonium nitrate (34-0-0). Using an N only starter may
provide an adequate response, but since P is immobile in the soil, sometimes additional P
may still need to be added in very close proximity to the seed for an ideal response. This
may be accomplished by the use of a very low rate of starter placed with the seed as a
pop-up fertilizer. This allows the developing seedling access to P without adding much to
the soil profile. Pop-up fertilizer will be discussed further in the placement section.
Rates. Generally, only a small amount of fertilizer will be required for a starter response if soil
fertility tests within the optimum range or higher. The appropriate rate of starter to use will
depend on: proximity to the seed, salt content or index, and soil texture. Using rates above
the recommended limit can cause a salt effect that can impede germination and early plant
development. If starter fertilizer is placed 2 inches from the seed, do not apply more than 70
lbs N plus K2O per acre and reduce even further if placed in closer proximity to seed. If
starter is placed with the seed (a pop-up fertilizer) the limit should be 10 lbs/acre. Salt index
is estimated to be the sum of N + K + 0.5 x S. These values are provided in Table 1.
Problems associated with salt damage may develop if soil moisture is limited within the first
few weeks after planting or if fertilizer was placed too close to the seed. Soil texture also
plays a role in that fertilizer rates must be lowered when placed within 1-2 inches on sandy
soils. Table 2 shows the amount of 10-34-0 that can be safely applied per acre of corn in
sandy versus non-sandy soils. It is especially important to follow rate limits in conservation
tillage due to the less accurate placement of starter in relation to the seed.
Table 1. Salt index for common starter
fertilizer materials relative to 10-34-0 and
expressed as pounds of salt effect per gallon.
Product
Salt index
lb/gal
Value relative
to 10-34-0
10-34-0
2.28
1.00
7-21-7
3.04
1.33
28-0-0
6.75
2.96
32-0-0
7.78
3.41
12-0-0-26
30.90
13.55
Source: Hergert, G.W., et al. 2012. Using starter fertilizers for
corn, grain sorghum, and soybeans. NebGuide. G361.
University of Nebraska.
(from Mortvedt, J.J. http://spectrumanalytic.com)
Table 2. Amount of 10-34-0 that can be safely
applied per acre for corn and grain sorghum
in 30-inch rows.*
10-34-0 (gal/acre)**
Soils
Starter Placement
Sandy
Non-Sandy
With the seed
(in-furrow or pop-up)
5
5
1/4 to 1/2 inch
from the seed
10
10
1 inch from the seed
20
40
2 inches from the seed
20+
40+
*For narrower row-widths, the application rate may be
increased. For 22-inch rows, multiply values by 1.36 and for
Placement. While N is mobile in the soil, P is bound and does not readily move through the
15-inch rows multiply by 2.
soil, therefore having a lesser chance of contacting soil roots. Starter fertilizer allows close
**Safe application rates for other starter formulations should
be determined.
placement of P in order for the developing plants to take it in. Placement is crucial because
seedling plants must be close enough to access nutrients, but not too close when used at
Source: Hergert, G.W., et al. 2012. Using starter fertilizers for
higher rates. The ideal placement for starter fertilizer is in a band 2 inches to the side of and 2 corn, grain sorghum and soybeans. NebGuide G361.
University of Nebraska.
inches below the seed (2x2). This allows the roots easy access to the fertilizer, but limits the
potential for fertilizer burn. The 2x2 placement has an advantage over seed-placed starter because not only is the position relative to nodal root
development more advantageous, but higher rates can be used without risk to the seed.
Alternatives to the 2x2 band include: placement at 2 inches beside and at the same depth as seed; dribbling fertilizer over the seed row in front of
the no-till coulter; and pop-up placement. “Pop-up” fertilizer which is placed directly in contact with the seed is an option, but requires extreme
caution to avoid germination or seedling injury. The amount used should be very limited and depends on the formulation and soil properties.
Possible advantages of pop-up placement include: no need for separate fertilizer opener on the planter, lower rate of fertilizer used, reduced
amount of P on high P soils, and less fertilizer handling (fewer planter fill-ups). However, it should be used with extreme caution due to the potential
for crop injury. No more than 10 lbs/acre N + K2O should be applied and neither diammonium phosphate (DAP – 18-46-0) nor urea (46-0-0) should
be used because of risk for seedling injury. Pop-up placement can be a good option if the proper rate and materials rules are followed and
equipment can be adequately set for pop-up placement.
Yield response to starter fertilizer use.
Research has shown great variance in the ability of starter fertilizer to result in grain yield increases, meaning that environmental and management
practices play a larger role in the crop’s final outcome. Studies have shown that situations most likely to experience yield response from the use of
starter fertilizer include: areas in the Northern Corn Belt and areas within the Central Corn Belt that used reduced tillage or have poorly drained
fields or soils testing low in P.
Sources: Beegle, D.B., et al. 2003. Starter fertilizer. Agronomy Facts 51. Penn State University. http://cropsoil.psu.edu (verified 2/10/14); Hergert, G.W. et al. 2012. Using starter fertilizer
for corn, grain sorghum, and soybeans. University of Nebraska–Lincoln. NebGuide. G361; Hoeft, R. 2000. Will starter fertilizer increase corn yield? University of Illinois Extension. The
Bulletin; Nielsen, R. 2013. Root development in young corn. Purdue University Department of Agronomy. www.agry.purdue.edu (verified 2/10/14).
Individual results may vary, and performance may vary from location to location and from year to year. This result may not be an indicator of results you may obtain as local growing, soil and
weather conditions may vary. Growers should evaluate data from multiple locations and years whenever possible. ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. Leaf
Design® is a registered trademark of Monsanto Company. Channel® and the Arrow Design® and Seedsmanship At Work® are registered trademarks of Channel Bio, LLC. ©2014 Monsanto
Company. 02182014JMG
Channel.com
For additional agronomic information, please contact your Channel Seedsman