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 government programs.

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.

Planting dates

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.

Planting Populations

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.

Weed Control

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 consultant.

Further Reading


Note: Web resources for Wisconsin are maintained by Mike Rankin and Team Forage. Please see for an up-to-date listing.

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
      Follow-up comments
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" fact sheet.

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

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