|Allmaras, Raymond - USDA-ARS (RETIRED)|
Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 6, 2004
Publication Date: July 1, 2005
Citation: Johnson, J.M., Reicosky, D.C., Allmaras, R.R., Sauer, T.J., Venterea, R.T., Dell, C.J. 2005. Greenhouse gas contributions and mitigation potential of agriculture in the Central USA. Soil & Tillage Research. 83(1):73-94. Interpretive Summary: The Central United States (MN, WI, IA, MI, IL, ID, OH, MO and parts of SD, ND, NE and PA) contain some of the most productive agricultural land of the world. A large proportion of land area in this region is committed to agriculture for crops especially corn and soybean or as managed grass lands such as pastures. This region represents a very large percentage of agricultural lands in the US. Soils can contribute greenhouse gases; e.g., carbon dioxide, nitrous oxide and methane. However, if managed properly, the amount of carbon stored in the soil can exceed the amount of carbon lost as carbon dioxide, returning the soil carbon level closer to original native levels. It is also possible to remove enough carbon dioxide from the atmosphere to offset global warming potential of nitrous oxide and methane released from agricultural systems. The large amount of agricultural land in the Central US means even small changes in the amount of carbon stored per acre can have a large impact on the over all contribution of agriculture to greenhouse gases in the atmosphere. This review addresses the current status of knowledge on how management such as tillage changes the rate of carbon storage and the amount of nitrous oxide and methane released. There is limited information on greenhouse gas emission from cropland or managed grass land. It points to the need for research on the interactions of tillage and fertilization on C storage and greenhouse gas offsets. This information will aid in determining how United States agriculture can help reduce greenhouse gas emissions and remove carbon dioxide from the atmosphere. In addition, helping producers improve their management options to achieve sustainable agriculture with food security, positive environmental benefits, productive soil, clean water and minimal impact on climate change will add to our quality of life.
Technical Abstract: The Central United States contains some of the most productive agricultural land of the world. Due to the high proportion of land area committed to crop land or pasture in this region, the C stored or greenhouse gas (GHG) emissions due to agriculture in the region represent a large percentage of the United States total. The objective of this work is to quantify the potential C sequestration and GHG emission and how tillage and cropping systems interact to modify these processes. Conservation tillage including no tillage systems have increased in the region, reducing the loss of organic matter rich topsoil and sequestering C. The rates of C storage in NT compared to conventional tillage are highly variable; averaging 630 kg C ha**-1 y**-1, for 21 treatment pairs in the Central US, which exceeds the global average for a humid region. Converting from continuous corn (CC) to three or more crops in rotation increased SOC an average of 140 kg C ha**-1 y**-1 (15 treatment pairs), but converting from CC to corn-soybean rotation decreased SOC an average of 150 kg C ha**-1 y**-1 (seven treatment pairs). An increase in N2O emissions of 2.1 kg N ha**-1 y**-1 would completely offset the sequestration of 300 kg C ha**-1 y**-1. Limited data on GHG emission from cropland or managed grazing land suggest the need to understand the interaction of tillage and fertilization on C sequestration and GHG emission offsets in cropland and managed grassland across the region.