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Dynamics of Dissolved Organic Carbon and Methane Emissions in a Flooded Rice Soil
Author(s) -
Lu Yahai,
Wassmann Reiner,
Neue Heinz-Ulrich,
Huang Changyong
Publication year - 2000
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/sssaj2000.6462011x
Subject(s) - dissolved organic carbon , dns root zone , oryza sativa , soil water , agronomy , chemistry , cultivar , poaceae , environmental science , environmental chemistry , biology , soil science , biochemistry , gene
Limited information is available on the dynamics of dissolved organic C (DOC) and its relationship with CH 4 emissions in flooded rice ( Oryza sativa L.) soils as affected by rice cultivar. Greenhouse and laboratory experiments were conducted to determine root C release in culture solution, DOC and dissolved CH 4 concentration in soil solution, and CH 4 emission in a flooded soil planted with three rice cultivars. Soil solutions were sampled in the root zone (soil surrounding rice roots) and the non‐root zone (soil outside the root zone). The release of root exudates increased in the order: IR65598 (new plant type) < IR72 (modern cultivar) < Dular (a traditional cultivar). Correspondingly, DOC concentrations in the root zone and CH 4 emission rates increased. The dynamics of DOC and dissolved CH 4 differed greatly between the root zone and the non‐root zone. Dissolved organic C in the root zone increased with plant growth and reached maximum (13–24 mmol C L −1 ) between rice flowering and maturation (Week 11–13), whereas DOC in the non‐root zone remained low (1–5 mmol C L −1 ) throughout the growing season. Similarly, dissolved CH 4 concentrations in the root zone increased sooner and were greater (mean 138 μmol CH 4 L −1 ) than those in the non‐root zone (mean 97 μmol CH 4 L −1 ). The seasonal patterns of CH 4 emissions closely followed the dynamics of DOC concentrations in the root zone. The results suggest that (i) DOC pool in the root zone of rice plants is enriched by root‐derived C; (ii) the rates of CH 4 emissions are positively correlated with the dynamics of DOC in the root zone; (iii) the intercultivar difference in root C releases is responsible for the intercultivar difference in DOC production, and consequently in CH 4 flux.