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Carbon Dynamics in Corn‐Soybean Sequences as Estimated from Natural Carbon‐13 Abundance
Author(s) -
Huggins D. R.,
Clapp C. E.,
Allmaras R. R.,
Lamb J. A.,
Layese M. F.
Publication year - 1998
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1998.03615995006200010026x
Subject(s) - loam , soil carbon , humus , agronomy , chemistry , total organic carbon , zoology , soil water , environmental science , biology , soil science , environmental chemistry
Carbon flow in terrestrial ecosystems regulates partitioning between soil organic C (SOC) and atmospheric CO 2 . Our objectives were to assess SOC dynamics using natural 13 C abundance in corn ( Zea mays L., a C 4 species)‐soybean [ Glycine max (L.) Merr., a C 3 species] sequences. Fifteen treatments of continuous corn, continuous soybean, various sequences of corn and soybean, and fallow were initiated in 1981 at Lamberton, MN, on a Webster clay loam (fine‐loamy, mixed, mesic Typic Haplaquoll). In 1991, soil and aboveground shoot samples from all treatments were analyzed for total organic C and δ 13 C. Carbon inputs, δ 13 C, and SOC were integrated into a two‐pool model to evaluate C dynamics of corn and soybean. Total SOC was similar across all treatments after 10 yr; however, differences in soil δ 13 C occurred between continuous corn (δ 13 C = −17.2‰) and continuous soybean (δ 13 C = −18.2‰). Modeled C dynamics showed SOC decay rates of 0.011 yr −1 for C 4 ‐derived C and 0.007 yr −1 for C 3 ‐derived C, and humification rates of 0.16 yr −1 for corn and 0.11 yr −1 for soybean. Decay and humification rates were slightly lower than those found in other Corn Belt studies. Levels of SOC were predicted to decline an additional 7 to 18% with current C inputs from either corn or soybean, respectively. Annual C additions required for SOC maintenance averaged 5.6 Mg C ha −1 , 1.4 to 2.1 times greater than previously reported estimates. Controlled variation in natural 13 C abundance in corn‐soybean rotations during a 10‐yr period adequately traced C dynamics.