Handling Corn in an "Emergency" Forage Season: Agronomic and Economic Considerations
July 1, 2004 11(17):116-117
Joe Lauer, Corn Agronomist
An â€œemergencyâ€ 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 â€œemergency.â€ 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 August 1
and the average killing frost date of October 7 is 1000 GDUs. Corn at V12 can yield
20% of a normal crop or about 1.5 to 2 T dry matter/A (Ritchie et al., 1993)
with 15% of the dry matter in leaves.
This year the 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 lbs N/A should be applied when
producing corn as emergency forage (Bundy, personal communication). No N may be
needed for corn following alfalfa.
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/A would be recommended for emergency
Little data exists for corn response to row spacing when late-planted. Using typical
planting dates, corn forage yield increases 7 to 9 % 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.
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 A (1994-2003). Budget estimates for corn
forage production of 6 T dry matter/A are slightly higher ranging from
$287 to $361 per A or $48 to $60 per T dry matter.
With projected savings of $40 per A and a yield level of 4 T dry matter/A, 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.
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.