Can corn silage be grown on highly erodible land and still meet "T" requirements for NRCS conservation plans? I was unable to find any studies that directly addressed this issue, but I found three studies that estimated percent ground cover from corn residue mass. By correlating these studies with cutting height studies conducted in Wisconsin we might be able to derive some general guidelines for managing corn silage on highly erodible land.

The relationship between corn silage cutting height, residue left after silage harvest and percent ground cover is shown in Table 1. As the cutter bar is raised on the silage chopper, the amount of corn residue remaining in the field is about 1 ton of dry matter per foot of residue height. So approximately 2 tons of dry matter per acre remains in the field when the cutter bar is raised 24 inches above the ground. Plant population, yield level and hybrid influence the amount of corn residue remaining after chopping,

Table 1. Relationship between corn silage cutting height, residue left after harvest and percent ground cover.
	Corn residue	Percent Ground Cover ^a
Cutting height	remaining in field ^b	Mean	Range
Inches	T/A	%
6	0.53	13	9 – 20
12	1.05	27	18 – 41
18	1.58	42	25 – 63
24	2.10	55	32 – 83
^aDerived from Gregory, 1982; Dickey et al., 1985; and Smith et al., 1990. ^bDerived from Cusicanqui, 1998 and Lauer et al., 2001.

Two tons dry matter per acre results in 55% ground cover, but much variability exists between reports (range = 32 – 83 %). Factors that influence percent ground cover include tillage system, time of year, type of residue, hybrid, environment, residue orientation and distribution, and row spacing. In all studies, leaving 2 tons dry matter per acre resulted in greater than 30% ground cover, which meets conservation requirements for highly erodible land. Fall and spring tillage and planting operations further reduce percent ground cover. Since percent ground cover for NRCS programs is measured after planting, these operations dictate whether residue left after raising the cutter bar will meet percent ground cover requirements the following spring.

The ability to meet "T" requirements for conservation plans depends upon numerous factors including slope, soil type, location, and the amount of soil disturbance from the tillage system. Before any change is implemented check with NRCS staff to confirm whether residue meets local conservation program requirements.

Literature Cited

Cusicanqui, J. A. 1998. Plant density, hybrid, and cutting height influence corn silage yield and quality. University of Wisconsin,

Dickey, Elbert C., David P. Shelton, Paul J. Jasa, and Thomas R. Peterson. 1985. Soil erosion from tillage systems used in soybean and corn residues. Transactions of the American Society of Agricultural Engineers 28:1124-1129.

Gregory, James M. 1982. Soil cover with various amounts and types of residue. Transactions of the American Society of Agricultural Engineers 25:1333-1337.

Lauer, J., K. Kohn, and P. Flannery. 2001. Studies on cultural practices and management systems for corn. 154 pages.

Smith, J. A., C. D. Yonts, M. D. Rath, and J. E. Bailie. 1990. Mass of crop residue and its relationship with soil cover for a corn, dry bean, and sugarbeet rotation. Transactions of the American Society of Agricultural Engineers 33:1503-1508.