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					Extension Responds: Flood
Handling Corn in an “Emergency” Forage Season:
Agronomic and Economic Considerations
By Joe Lauer, Extension Professor of Agronomy, University of Wisconsin-Madison, UW-Extension Corn
Agronomist, 608-263-7438, jglauer@wisc.edu

An “emergency” forage situation occurs when farmers have abandoned hope for grain
production and use a crop only for its stover (leaves and stalks). Grain yield is usually
not possible or minimal due to late planting and the amount of growing season
remaining. In Wisconsin corn grain production is minimal after June 20. After June 20,
corn should only be considered if it is a forage “emergency.” This article will discuss
some of the agronomic and economic factors that should be considered for farmers
choosing corn for forage.

How late can corn planting occur?
Corn at the V12 stage is similar in height to small grains. To achieve the V12 stage of
growth 815 GDUs are required. At Arlington, GDU accumulation between Aug. 1 and
the average killing frost date of Oct. 7 is 1000 GDUs. Corn at V12 can yield 20 percent
of a normal crop or about 1.5 to 2 T dry matter/A (Ritchie et al., 1993) with 15 percent of
the dry matter in leaves.

Soil Fertility
This year the nitrogen (N) loss processes that occur with wet conditions have reduced
inherent soil N levels and the soil’s ability to contribute N for plant needs. In an
emergency situation, using starter fertilizer (10-20-20) will help corn plants grow faster.
Since corn forage yield will be reduced, N rates can be reduced, but corn is a N-
responsive plant, so some N will be required. At least 40 to 50 pounds per acre should
be applied when producing corn as emergency forage (Bundy, personal
communication). No N may be needed for corn following alfalfa.

Plant density
Corn forage yield increases with increasing plant density, but the trade-off is that corn
forage quality decreases. In an emergency situation where only stover is produced,
quality is most influenced by hybrid maturity and frost-kill date, so one need not be
overly concerned about the trade-off between plant density and quality. Plant densities
of 40 000 to 50 000 plants per acre would be recommended for emergency corn forage.

Row spacing
Little data exists for corn response to row spacing when late-planted. Using typical
planting dates, corn forage yield increases 7 to 9 percent as row spacing decreases
from 30 to 15 inches. A slightly smaller yield response would be expected with
emergency conditions since no grain yield would be produced.
Since corn forage responds to higher plant density and to further reduce production
costs, a grain drill might be considered. Applying starter fertilizer will be difficult and
correct calibration of the drill will be important, as small changes in the seed meter will
result in large plant density changes.

Pest Control
It is usually easier to control weeds in late corn plantings than in early plantings. Late
tillage kills many germinated weeds and corn seedlings are more competitive due to
warmer temperatures.

Insects normally are a greater threat to late plantings than weeds. Use a seed
treatment for seed corn maggot since 4 to 5 generations can hatch over the growing
season. No soil rootworm insecticide will need to be applied, since the corn rootworm
hatch is usually complete by mid-June and the larvae die within 48 hours if no corn
roots are present (Jensen, personal communication). Scout for cutworm and second-
generation European corn borers.

Cost of Production
Acre cost of production for emergency corn forage would be lower than normal corn
forage, but more expensive on a per unit yield basis. Corn forage planted on July 1
could reasonably be expected to yield 4 T dry matter/A.

Cost savings could occur with soil fertility, pest control, and equipment (if a grain drill is
used). Seed costs would increase slightly if higher plant density was used. Lower yields
would in turn reduce chopping and hauling costs. Input savings for emergency corn
forage production of $20 to $60 might be reasonably expected.

Average cost of production for corn grain in the PEPS Cash and Livestock program is
$277 to $225 per acre (1994-2003). Budget estimates for corn forage production of 6 T
dry matter per acre are slightly higher ranging from $287 to $361 per acre or $48 to $60
per tons of dry matter (source: Center for Dairy Profitability ABCS Budgets at
http://cdp.wisc.edu/pdf/cornalf.pdf and http://cdp.wisc.edu/pdf/corncorn.pdf).

With projected savings of $40 per acre and a yield level of 4 tons of dry matter per acre,
emergency corn forage would cost $62 to $80 per T dry matter, which is about $14 to
$20 per T dry matter higher than normal corn forage. Forage quality of emergency
forage would be only slightly lower than normal corn forage quality.


                                       Literature Cited

Ritchie, S. W., J. J. Hanway, and G. O. Benson. 1993. How a corn plant develops. Iowa
       State University CES Special Report No. 48. 21 pp.

For more information: Joe Lauer, 608-263-7438, jglauer@wisc.edu

				
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