Overview

Corn is one of the most extensively grown crops in the United States, with some production in almost every state. Corn can be harvested either for grain or for silage, depending on markets, weather and other environmental conditions. The highest acreage of corn harvested for grain occurs in the Midwest states of Iowa, Illinois, Indiana, Minnesota and Nebraska, with production area in South Dakota and Kansas increasing over the past 15 years. The summary graphic for corn grain indicates improvements over time in most indicators, with that improvement slowing over time and stalling for soil erosion in the 2010s (Figure 1.2.1). A summary of all corn for grain indicators is shown in Table 1.2.1. Figure 1.2.1. Summary chart of indicators for corn grain 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 grain 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 has increased since the late 1980s but plateaued during the 2010s (Figure 1.2.2), while total production has continued to increase (Figure 1.2.3). The land use indicator reflects this increasing yield trend, demonstrating that it takes less land to produce a bushel of corn in 2020 than in 1980 (Figure 1.2.4). The trend for the 2010-2020 period is largely influenced by the low yields of 2012 in response to extreme weather events. There is a flattening of the land use efficiency indicator from 2014 to 2020, indicating a plateau in the yield improvement trend.

Energy Use

Energy use efficiency has improved throughout the period of analysis up until 2010; however, since 2014, corn energy use efficiency has plateaued (Figure 1.2.5). The energy use per acre indicates a leveling off and slight increase in energy use for corn production (Figure B.5). This may reflect the increase in inputs, in particular, fertilizers, fungicides and herbicides, since the year 2000.

Greenhouse Gas Emissions

GHG emissions per bushel of corn (Figure 1.2.6) largely follows the energy use trend for corn, with the major contributor being nitrous oxide emissions (Figure B.8). Small GHG emission increases per acre (Figure B.7) since 2000 can be attributed in part to the factors behind the plateauing of energy use, with the additional contribution of higher fertilizer nitrogen applications leading to greater nitrous oxide emissions. While manure is applied to corn grain, it contributes less than 5% of the total nitrogen applied in the most recent decade; therefore, the nitrous oxide emissions increase is largely driven by synthetic nitrogen applications, which have been rising steadily since 2000. The top four contributors for energy use and GHG emissions for corn grain during 2010 to 2020 are listed in Table 1.2.2.

Irrigation Water Use

Irrigation water use efficiency fluctuated in the first half of the study period as the area planted to corn expanded and reached a high value in the mid-1990s (Figure 1.2.7). Since then, the irrigation water use efficiency has improved steadily for corn. The average irrigated harvested acreage across the 2008, 2013 and 2018 Irrigation and Water Management Survey for corn grain was approximately 15% of the total harvested acres.

Soil Erosion

Soil erosion for corn grain has largely plateaued since 2000 (Figure 1.2.8). While substantial improvements were seen in the period from 1980 to 2000, those have not continued. One major driver is tillage, and available data indicate that the share of corn under conventional tillage practices remains over 30%, with another 40% in a reduced tillage system and less than 30% under no tillage. Shifts over time in the location of production to areas farther west-which may be more susceptible to wind erosion-may also be influencing this trend. Download Corn for Grain Data Barley Corn for Silage