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Stabilization of 13 C‐Carbon and Immobilization of 15 N‐Nitrogen from Rice Straw in Humic Fractions
Author(s) -
Bird Jeffrey A.,
Kessel Chris,
Horwath William R.
Publication year - 2003
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/sssaj2003.8060
Subject(s) - straw , chemistry , agronomy , crop residue , nitrogen , residue (chemistry) , organic matter , oryza sativa , soil carbon , nutrient , zoology , soil water , environmental science , biology , soil science , ecology , organic chemistry , biochemistry , gene , agriculture
The transition from open‐field burning of straw residues to alternative residue management practices may affect soil C sequestration potential and the supply of nutrients to crops. A field study of dual‐labeled ( 13 C and 15 N) rice ( Oryza sativa L.) residues examined the effects of winter‐fallow flooding (vs. nonflooded) and straw residue incorporation (vs. untilled, open‐field burned residue) on straw C and N dynamics in soil organic matter (SOM) fractions. We examined the fate of C and N in the straw, crown, and root system in the incorporated treatments and the uncombusted stubble, crown, and roots in burned treatments during 1 yr. During the winter fallow, straw residue incorporation reduced residue 15 N loss but increased residue 13 C loss compared with burning. Straw 13 C loss after 1 yr was unaffected by either winter flooding or straw management (77.1% of applied). Slightly more straw 15 N was lost of that applied in burned (65.5 ± 3.5%) compared with incorporated (52.0 ± 3.8%) during 1 yr. A greater proportion of soil‐recovered 13 C remained as nonalkali extractable humics (humin) in burned (62.0%) compared with incorporated (40.8%). In contrast, incorporated treatments had a larger proportion of 15 N remaining as mobile humic acid (MHA) than burned (42.4 vs. 37.7%). Straw incorporation increased the relative retention of straw 15 N to 13 C compared with burning, indicating that straw 15 N additions with incorporation may increase soil organic N reserves at an even greater rate than the larger straw additions might predict. These results show that straw incorporation results in markedly different straw C and N sequestration pathways compared with untilled, open‐field burned residues.