Overview

Corn is also grown for silage for animal feed. Silage corn production practices are similar to those for corn grain in the first part of the growing season, but the entire stalk is harvested earlier in the season leaving far less crop residue after harvest. Therefore, we consider it here as a separate cropping system than corn for grain. A producer may decide partway through the season to harvest the corn crop as silage, rather than wait to harvest as grain, depending on market and weather conditions. Silage corn is grown in almost every U.S. state, with high production in the upper Midwest states and other large dairy states, including New York, Pennsylvania and California. 

The summary chart for corn silage illustrates overall improvements in energy use and land use but with a recent reversal in the energy use trend and a fluctuation over time in irrigation water use (Figure 1.3.1). A summary of all indicators for corn silage for reference years is shown in Table 1.3.1. Note that the soil erosion indicator for corn silage is the same data as presented for corn grain and is discussed in the previous section (for more information see Appendix A, section Corn for Grain and Silage). Figure 1.3.1. Summary chart of indicators for corn silage during 1980-2020 Data are presented in index form, where all indicators have been scaled by indicators averages for the period 1998 to 2002. A 0.1 point change is equal to a 10% difference. Index values allow for comparison of change across indicators with different units of measure. A smaller area represents improvement over time. Additional illustrations of corn for silage sustainability on a per acre basis and for total resource use are available in Appendix B, accessible from the Download Report link. 

Land Use

Area planted to corn for silage declined from 1980 to 1990, was roughly level until around 2010, and has started to increase in recent years (Figure 1.3.2). Overall, total production of corn silage has increased since 1990 (Figure 1.3.3). There are several spikes in the acreage data (Figure 1.3.2) likely attributed to weather events where corn planted initially for grain was instead harvested for silage to avoid economic loss of the entire crop. One such spike was observed in 2012, a year with severe drought. The land use efficiency of corn silage production has steadily improved since 1990, indicating increasing yields per acre harvested (Figure 1.3.4).

Energy Use

Overall energy use efficiency has improved through 2010 for corn silage, with a leveling off in the past decade (Figure 1.3.5). Energy embedded in the production of fertilizers and field operations (management) are the major components for the energy use efficiency indicator (Figure B.10).

Greenhouse Gas Emissions

Emissions associated with corn silage production do not show a clear trend, with emissions per unit of yield lower in 2020 than in 1980 but with the lowest values achieved in the 1990s (Figure 1.3.6). Emissions per acre have increased since 2000 (Figure B.11), with the primary component of increase being nitrous oxide emissions. Nitrogen content from manure applied to fertilize corn for silage has a considerable impact. The top four contributors for corn silage for energy use and GHG emissions during 2010 to 2020 are listed in Table 1.3.2.

Irrigation Water Use

Irrigation water use efficiency for corn silage does not show a clear trend (Figure 1.3.7). The water use efficiency in 2020 is lower than that in the late 1980s, following variable patterns in the subsequent years. The trend is similar to that for corn grain. Over time, the share of irrigated acreage for corn silage has been increasing. The average irrigated harvested acres across the 2008, 2013 and 2018 Irrigation and Water Management Survey for corn silage was approximately 27% of the total harvested acres. Download Corn for Silage Data