Maximum soil organic carbon storage in Midwest U.S. cropping systems when crops are optimally nitrogen-fertilized

• Published in: PloS one Vol. 12; no. 3; p. e0172293
• Main Authors: Poffenbarger, Hanna J., Barker, Daniel W., Helmers, Matthew J., Miguez, Fernando E., Olk, Daniel C., Sawyer, John E., Six, Johan, Castellano, Michael J.
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01.03.2017; Public Library of Science (PLoS)
• Subjects: Agricultural land; Agricultural production; Agriculture; Agronomy; Analysis; annuals; Biology and Life Sciences; Carbon; Carbon sequestration; Carbon storage; continuous cropping; Corn; Crop Production - methods; Crop residues; Crop yield; cropland; Cropping systems; Crops; Ecology and Environmental Sciences; Emissions; Evaluation; Experiments; Farms; Fertilization; fertilizer rates; Fertilizers; Glycine max; Glycine max - growth & development; Iowa; Midwestern United States; Mineralization; Nitrogen; nitrogen fertilizers; Optimization; Organic carbon; Organic soils; People and places; Physiological aspects; Precipitation; Research and Analysis Methods; Soil; Soil carbon; soil organic carbon; Soils; Soybeans; Zea mays; Zea mays - growth & development; United States; Midwest states; Iowa
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0172293

Nitrogen fertilization is critical to optimize short-term crop yield, but its long-term effect on soil organic C (SOC) is uncertain. Here, we clarify the impact of N fertilization on SOC in typical maize-based (Zea mays L.) Midwest U.S. cropping systems by accounting for site-to-site variability in maize yield response to N fertilization. Within continuous maize and maize-soybean [Glycine max (L.) Merr.] systems at four Iowa locations, we evaluated changes in surface SOC over 14 to 16 years across a range of N fertilizer rates empirically determined to be insufficient, optimum, or excessive for maximum maize yield. Soil organic C balances were negative where no N was applied but neutral (maize-soybean) or positive (continuous maize) at the agronomic optimum N rate (AONR). For continuous maize, the rate of SOC storage increased with increasing N rate, reaching a maximum at the AONR and decreasing above the AONR. Greater SOC storage in the optimally fertilized continuous maize system than in the optimally fertilized maize-soybean system was attributed to greater crop residue production and greater SOC storage efficiency in the continuous maize system. Mean annual crop residue production at the AONR was 22% greater in the continuous maize system than in the maize-soybean system and the rate of SOC storage per unit residue C input was 58% greater in the monocrop system. Our results demonstrate that agronomic optimum N fertilization is critical to maintain or increase SOC of Midwest U.S. cropland.