The objectives of tillage are to control weeds, level land, and loosen
soil. A wide variety of tillage systems have been used to produce corn
silage successfully. Traditional tillage systems incorporate nearly all
crop residue while conservation tillage systems leave at least 30% of
the soil surface covered by crop residue at planting.
Conservation tillage systems are gaining wide acceptance throughout the
country as a valid method for reducing soil erosion. Other benefits
include increased water availability during drought, improved water
quality, and lower costs for fuel, equipment, and labor. The use of
conservation tillage systems for corn silage is often complicated by the
need to spread manure and the increased potential for soil compaction
from silage wagon or trucks. Also, the lack of residue left on the field
after silage harvest may prevent some growers from participating in
Special considerations for conservation tillage systems.
Select hybrids adapted to the area with good seedling vigor. In
short-season areas, tillage systems with more than 75% crop residue
require short-season hybrid (about 5 less relative maturity units) due
to slower crop emergence. An uneven soil surface, insects, rodents,
disease, and cooler soil temperatures tend to reduce seed germination
and emergence. Seeding rates that are 10 to15% higher can offset the
greater seedling mortality typically observed in conservation tillage
plantings. Scout fields to determine pest problems and severity and then
take appropriate control measures. Starter fertilizers placed below and
to the side will help the seedling overcome slow early growth when soil
conditions are cool and wet under residue.
Cover crops such as rye, wheat, spring oats, and triticale have all been
used successfully to provide some winter cover on the soil and to take
up some of the excess nitrogen not used by the corn crop. The cover
crops can then be either harvested, incorporated, or burned down with a
herbicide the following spring. In short growing season areas, rye cover
crops may stunt corn growth when the rye has been allowed to grow above
12 to 15 inches before being incorporated or killed with a herbicide.
Early plantings give higher grain and corn silage yields. However, the
advantages of early planting for silage are often not as great as for
grain. High grain moisture at harvest and low tst weight of late-planted
corn that may be a problem for grain producers are not generally a
problem in corn silage production. Planting date studies for corn silage
in New York and Pennsylvania recently showed that delaying planning two
weeks until late May had little effect on forage quality but in three of
four years reduced yields by 1.5 tons/acre compared to an early May
planting. Later plantings can predispose the crop to frost before
maturity and an increased potential for drought stress or insect damage
in some areas. Grain content and digestibility can be reduced if delayed
planting results in an immature crop killed by frost.
Corn planted for silage does not encounter the costs associated with
higher grain moisture at harvest, and there is less risk of reduced
quality due to frost as there is with corn for grain. Therefore, plant
corn destined for grain production first. In areas with longer growing
seasons, corn planted for silage can often be planted into early summer
and still produce profitable silage yields. In many of these areas corn
can be double cropped after barley or wheat with good success provided
adequate moisture is available. In the Southeast, corn can be double or
triple cropped, however later plantings are often subject to increased
insect, disease, and drought stress.
Corn silage yields usually increase more given higher plant populations
than do corn grain yields. Increasing plant populations by 10 to 20%
over those recommended for grain will often maximize silage yields.
Optimum plant populations will vary depending on region, but often
populations of 28,000 to 32,000 plants per acre are necessary to reach
maximum yields. The effects of increased population on fiber content,
digestibility, and protein concentration are generally small.
In many areas of the United States, corn crops need irrigation to supply
enough water for maximum production. Irrigation must supplement
evapotranspiration demands of the corn crop. The term evapotranspiration
refers to the water lost from the soil surface through evaporation and
the water used by a plant during transpiration. Efficient irrigation
management depends on knowing how much water is needed during the
various stages of corn growth and when to apply it. Figure 2 illustrates
the changing water needs throughout the life of the corn plant. Maximum
evapotranspiration will range from 0.15 to 0.35 inches per day depending
on environmental conditions.
Insufficient water at any time during plant growth will reduce silage
and grain yields. The extent of yield losses depends on the stage of
plant development. Water stress during vegetative development reduces
plant height and leaf area, although the effects on yield are less than
when water stress occurs at later stages. Water stress during grain
filling increases leaf loss and lodging, shortens the grain filling
period, and lowers kernel weight. Since silage quality is influenced by
the amount of grain in the silage, adequate water must be present during
tasseling, silking, and pollination.
Appropriate weed control programs should be used to control weeds for a
variety of reasons. Competition from weeds reduces yield, digestibility,
and protein content of silage. North Carolina trials found a steady
decline in digestibility based on the percentage of johnsongrass in the
silage (figure 3). Severe infestations of some weeds such as horsenettle
and hemp dogbane can produce toxic compounds in the silage. furthermore,
weed seeds present in the silage may be spread in the manure, spreading
troublesome weed problems to other fields or farms.
Harvesting corn for silage can also provide opportunities for weed
control that are not possible following grain harvest. For example,
perennial weeds such as quackgrass can often be killed with a timely
fall herbicide application following harvest. Scouting corn silage
fields for problem areas immediately after harvest can aid in an
effective weed control program. For detailed information on setting up a
weed control program, contact your county Extension agent or crop
Note: Web resources for Wisconsin are maintained by Mike Rankin and
Team Forage. Please see http://www.uwex.edu/ces/crops/uwforage/Silage.htm for an up-to-date
Corn plant density for maximum grain and silage production
by Dr. Joe Lauer, UWEX Agronomy Advice, April, 2009
Planting Corn in June and July! – What can you expect?
by Dr. Joe Lauer, UWEX Agronomy Advice, June, 2008
Planting Corn For Silage Following Winter-Killed Alfalfa
by Dr. Joe Lauer, Wisconsin Crop Manager Article, April, 2003
Planting Corn for Silage After a First-cut Alfalfa Harvest
by Mike Rankin, Crops and Soils Agent - Fond du Lac Co., Joe Lauer, UW-Extension Corn Agronomist, and Jerry Doll, UW-Extension Weed Management Specialist.
A "Focus on Forage" fact sheet.
Drought Stress Reduces Corn Silage Yield More Than Quality
by Dr. Joe Lauer, UWEX Agronomy Advice, August, 2007
Impact of Defoliation on Corn Forage Quality
by Dr. Joe Lauer, UWEX Agronomy Advice, August, 2007
Managing Corn Silage on Highly Erodible Land
by Dr. Joe Lauer, Wisconsin Crop Manager Article, April and June, 2002
Current Agronomic Research Related to Corn Silage
by Dr. Joe Lauer, UW Corn Agronomist.
Assessing the Impact of ECB on Corn Grown for Silage
by Scott Myers and John Wedberg, UW Dept. of Entomology, and Mike Ballweg, Crops and Soils Agent, UW-Extension-Sheboygan County. A "Focus on Forage"
How Late Should Corn Be Planted For Silage Production?
by Dr. Joe Lauer, Wisconsin Crop Manager Article, May, 1999
Corn Silage Response to Planting Date
by Dr. Joe Lauer, Wisconsin Crop Manager Article, June, 1998
Narrow Row Corn Silage Update
by Mike Rankin, Crops and Soils Agent, UW-Extension-Fond du Lac County
How Thick Should I Plant My Corn for Corn Silage Production?
by Dr. Joe Lauer, UWEX Agronomy Advice, April, 1997