Acres of Illinois corn harvested as corn silage in 2006 were 105,000 according to the Illinois Agricultural Statistics. Growers of corn silage have asked questions regarding the rate of nitrogen fertilizer for the crop.

Considerable data from Illinois exists on the effect of nitrogen on the yield of corn grain, but there is limited data on the effect on corn silage. With this in mind, a four year (2005-2008) study was conducted at the Northern Illinois Agronomy Research Center, Shabbona to measure the effect of nitrogen on the yield and quality of corn silage.

The study consisted of one hybrid per year planted in 30-inch rows in corn following corn (C-C) and in corn following soybean (Sb-C). Corn in both rotations received 0, 45, 90, 135,180, and 225 pounds of nitrogen per acre. The nitrogen was applied as urea ammonium nitrate solution dribbled between the rows followed by cultivation.

The following observations were made from the study.

1. Silage yield and crude protein were higher in Sb-C than C-C.
2. Silage yield and crude protein responded up to 180 pounds of nitrogen per acre in both Sb-C and C-C.
3. Neutral detergent fiber decreased in both rotations with increasing nitrogen rates.
4. The effect of nitrogen and rotation on other quality parameters (whole plant starch, in vitro dry matter digestibility, and neutral detergent fiber digestibility in a 30-hour test) was inconsistent, not distinct, or minimal.

Further details or information on the study is available from Jim Morrison, Extension Educator, Crop Systems at the Rockford Extension Center, phone 815-395-5710, or email morrison@illinois.edu