Carbon balances in US croplands during the last two decades of the twentieth century

• Published in: Biogeochemistry Vol. 107; no. 1-3; pp. 207 - 225
• Main Authors: Lokupitiya, E, Paustian, K, Easter, M, Williams, S, Andrén, O, Kätterer, T
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer-Verlag 01.02.2012; Springer; Springer Netherlands; Springer Nature B.V
• Subjects: Agricultural land; Agricultural Science; Agricultural soils; Agroecosystems; Agrology; American history; atmospheric precipitation; Biogeosciences; Carbon; Carbon dioxide; Carbon dioxide emissions; carbon footprint; carbon sinks; Crop management; Crop production; Crop residues; Crops; deltas; Earth and Environmental Science; Earth Sciences; Earth, ocean, space; Ecosystems; Engineering and environment geology. Geothermics; Environmental Chemistry; Exact sciences and technology; Farm buildings; Farmlands; Geochemistry; greenhouse gas emissions; Greenhouse gases; Growing season; Growing seasons; Jordbruksvetenskap; Life Sciences; magnesium; Marine and continental quaternary; Organic matter; Organic soils; plains; Pollution, environment geology; primary productivity; Residues; Soil; Soil and rock geochemistry; soil heterogeneity; Soil organic carbon; Soil organic matter; soil respiration; Soils; spatial variation; Surficial geology; Temperature; temporal variation; United States; USA, North Central Region; USA; Climate change; Carbon budgets; Agriculture; Cropland carbon cycling; Regional and national scale; atmosphere; carbon dioxide; models; respiration; carbon cycle; North America; agriculture; carbon; ecosystems; plains; organic materials; temperature; data bases; primary productivity; soils; strategy; climate change
• ISSN: 0168-2563; 1573-515X; 1573-515X
• DOI: 10.1007/s10533-010-9546-y

Carbon (C) added to soil as organic matter in crop residues and carbon emitted to the atmosphere as CO2 in soil respiration are key determinants of the C balance in cropland ecosystems. We used complete and comprehensive county-level yields and area data to estimate and analyze the spatial and temporal variability of regional and national scale residue C inputs, net primary productivity (NPP), and C stocks in US croplands from 1982 to 1997. Annual residue C inputs were highest in the North Central and Central and Northern Plains regions that comprise ~70% of US cropland. Average residue C inputs ranged from 1.8 (Delta States) to 3.0 (North Central region) Mg C ha−1 year−1, and average NPP ranged from 3.1 (Delta States) to 5.4 (Far West region) Mg C ha−1 year−1. Residue C inputs tended to be inversely proportional to the mean growing season temperature. A quadratic relationship incorporating the growing season mean temperature and total precipitation closely predicted the variation in residue C inputs in the North Central region and Central and Northern Plains. We analyzed the soil C balance using the crop residue database and the Introductory Carbon Balance regional Model (ICBMr). Soil C stocks (0–20 cm) on permanent cropland ranged between 3.07 and 3.1 Pg during the study period, with an average increase of ~4 Tg C year−1, during the 1990s. Interannual variability in soil C stocks ranged from 0 to 20 Tg C (across a mean C stock of 3.08 ± 0.01 Pg) during the study period; interannual variability in residue C inputs varied between 1 and 43 Tg C (across a mean input of 220 ± 19 Tg). Such interannual variation has implications for national estimates of CO2 emissions from cropland soils needed for implementation of greenhouse gas (GHG) mitigation strategies involving agriculture.