Starter Fertilizers for Corn Production
Table of Contents
Corn starter fertilizers have been used successfully to increase early plant growth, nutrient uptake, and yields in research trials and on the farm. They also promote earlier maturity, improve southern corn billbug control, and help suppress weeds through earlier shading. Use of starter fertilizers is increasing in North Carolina and the southeastern United States. This fact sheet presents the principles of successful starter fertilizer use, research results relevant to North Carolina, and management suggestions for corn producers.
Cool air and soil slow corn plant and root growth in the spring. When
root growth is restricted, corn plants often turn purple. Early season
purpling varies with variety, but most often it is a symptom of an induced
In most cases, phosphorus deficiencies are temporary, and symptoms disappear
as soon as soil temperatures rise to a point where root growth is stimulated
and the plant can reach more phosphorus. Grain yields are not reduced
every year by root stunting, but yield losses can be significant in years
when temperatures are low. Additional factors that limit root growth can
also induce phosphorus deficiencies. Some common causes include soil compaction,
herbicide injury, and insect or nematode damage to the
Starter fertilizers may be used to overcome slow root growth and the
potential for reduced nutrient uptake. Starter and "pop-up"
fertilizers involve at-planting placement of a small supply of nutrients
near the seed (for starter fertilizer) or in the seed furrow (for pop-up
types) so seedling roots can rapidly reach the nutrient source. These
fertilizers are not intended to supply all nutrients needed by the crop.
Their primary purpose is to provide an accessible nutrient source for
root and plant growth when adverse conditions occur soon
A field's yield potential, soil nutrient reserves, and fertilizer management
programs will dictate the best combination of nutrients for use in a corn
starter fertilizer. It is best to fine tune your starter needs by comparing
various nutrient combinations and starter rates on your own farm. The
best tools for evaluating starter fertilizer performance are a comprehensive
plant tissue analysis program and comparison of
Most research in the Southeast supports the practice of including nitrogen
and phosphorus in corn starter fertilizers. Research in South Carolina
compared several elements in corn starter fertilizers applied
Furthermore, the addition of micronutrients, potassium, or sulfur to
the starter did not improve yields over the nitrogen-phosphorus combination.
Soil tests at these experimental sites did not call for micronutrient
applications. If soil tests, field history, or past tissue analyses predict
a micronutrient deficiency, adding a suitable micronutrient source to
the starter fertilizer may be warranted. Lower micronutrient rates are
needed for banded starters than for broadcast applications. The most common
micronutrients needed on corn are manganese and zinc. Recommended starter
Support for including both nitrogen and phosphorus in starter fertilizers
has come from several southeastern states. Participants in a regional
workshop on corn starter fertilizers observed positive yield responses
to starter fertilizers in 78 percent of research and
Conclusions from the workshop stated that, over time, positive responses
to starter fertilizers appear to be more consistent for nitrogen alone
than for phosphorous alone. However, combining nitrogen with phosphorus
in a starter fertilizer is generally the most
Materials commonly used in starter fertilizers include diammonium phosphate
Two later studies in South Carolina and Alabama examined nitrogen and
phosphorus rates in corn starter fertilizers. Both programs were conducted
on Norfolk soils with high to very high phosphorus levels. Results from
six tests were similar for the two states. Corn responses to starter fertilizers
were more consistent for nitrogen alone than for phosphorus alone, and
yields were generally greater at all nitrogen rates with the addition
This fertilization management scheme would improve nitrogen use efficiency,
reduce potential nitrogen leaching losses, and provide a mechanism for
reducing phosphorus application rates on soils that test high in phosphorus.
The desired starter fertilizer analysis can be achieved by blending dry
granular materials such as DAP with ammonium nitrate or urea. Another
option is to use fluid starter fertilizers by blending products such as
On soils testing medium or low in phosphorus, higher phosphate rates
may be needed in the starter fertilizer. On medium-phosphorus soils, adding
The adoption of starter fertilizers on the farm is often hampered by
problems that arise when installing application equipment. The following
section offers several
Two-by-Two Placement. The most common starter placement is
All 2-by-2 placement units should be mounted in a manner that will allow them to "float" with the planter. Planter bar and unit spacings often make it difficult to install additional fertilizer attachments; thus, many are placed on forward-mounted tool bars. Forward mounting of starter fertilizer equipment decreases the precision of the placement on rough or rolling ground. These mechanical constraints and the expense of application equipment for placement has prompted researchers and producers to try the alternative placement methods, as described in the following paragraphs.
With liquid application units, care should be taken to prevent the liquid
fertilizers from adhering to the subsoiler shank. When this occurs, the
liquid starter drips down to the subsoiler shoe and is unavailable for
early plant growth. Splatter shields can be welded at specified depths
on the subsoiler, or a
When granular fertilizers are used, materials should be allowed to fall
freely into the subsoil track from a height
In-furrow placement (Figure 2c) of fertilizer with the seed
requires simple equipment but may result in fertilizer injury (Table 1).
Fertilizers applied with this technique are commonly referred to as "pop-up"
fertilizers. Pop-up fertilization is not recommended in North Carolina.
However, some growers working with organic soils have used
Surface banding over the row
Banding under the row
Plant growth and nutrient uptake can be influenced by placement method
Final grain yields can also be affected by
starter placement. In Florida, the
Starter fertilizers do not always increase
corn yields. They do, however, offer agronomic advantages that are often
overlooked. A North Carolina study showed that applying
Starter fertilizers also contribute to improved
insect and weed control. In the North Carolina coastal plain, the southern
corn billbug can be a major problem. When starter fertilizers are used,
early-season plant growth is rapid, and stand loss to billbug injury may
be reduced because larger plants are more tolerant of the insect's attack.
Improved weed control may be another benefit of using a starter fertilizer.
The rapid, early-season growth stimulated by starter fertilizers helps
corn to compete more effectively with weeds and may reduce the need to
Few states have tested the response of different
hybrids to starter fertilizers. The most comprehensive study in the Southeast,
conducted in Florida, compared
The Florida researchers also looked at the
influence of starter fertilizers on plant lodging. They concluded that
lodging was reduced with starters regardless of the hybrid used. Thus,
it is important to know that hybrids do respond differently to starter
fertilizers. To determine which hybrids are responsive, you may want to
conduct simple tests on your
Other factors that may influence corn response to starter fertilizers include the tillage method, soil type, soil fertility status, and yield potential. In general, if conditions promote soil compaction and prevent early-season soil warming, corn will respond positively to the starter fertilizers. For example, no-till corn appears to be more responsive to starter fertilization than corn grown in conventional tillage systems. Corn grown on clay soils with high phosphorus fixing capacities and soils with low levels of plant-available phosphorus are also likely to respond more favorably to starters containing phosphorus. It is also important to note that conditions that limit growth or yield potential may reduce plant responses to starter fertilizers. Poor stands, insect or nematode damage, or drought may nullify the effects of starter fertilizers.
Starter fertilizers provide another management
tool that may increase yields or improve the profitability of corn production.
Starter fertilizers can be applied several ways, depending on producer
preference and the mechanical flexibility of the equipment. A starter
fertilizer should contain nitrogen and possibly phosphorus. Nitrogen and
phosphorus rates can be adjusted to optimize starter response on
The addition of other elements should be based on site-specific soil nutrient needs. The various corn hybrids respond differently to starter fertilizers: some positively, some negatively, and some not at all. Many physical and environmental conditions that reduce nutrient uptake can be offset, in part, by the use of a starter fertilizer. Starter fertilizers promise to be a valuable tool for minimizing the environmental impact of corn production.
The use of brand names in this publication
does not imply endorsement of the products or services named or criticism
of similar ones