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Major Biogeochemical Processes in Soils‐A Microcosm Incubation from Reducing to Oxidizing Conditions

2007; Wiley; Volume: 71; Issue: 4 Linguagem: Inglês

10.2136/sssaj2006.0155

1435-0661

Kewei Yu, Frank Böhme, Jörg Rinklebe, H. U. Neue, Ronald D. DeLaune,

Clay minerals and soil interactions

Six soils used for rice ( Oryza sativa L.) production were incubated using an automatic microcosm system. Production of trace gases (CO 2 , CH 4 , and N 2 O) and transformation of N, S, and metals (Fe and Mn) were studied in soil suspensions incubated from reducing to oxidizing conditions. Results show that soil pH variation was inversely correlated to soil redox potential (E H ) change ( P < 0.01). Soil CO 2 production exponentially increased with soil E H increase. In contrast, soil CH 4 production and DOC showed an exponential decrease with soil E H increase. Without the presence of soil oxidants, methanogenesis occurred across the entire E H range, with probable H 2 –supported methanogenesis at higher soil E H conditions constituting up to 200f total CH 4 production. The CH 4 compensation point, where CH 4 concentration became constant due to equilibrium between CH 4 production and consumption, exponentially decreased with soil E H increase. At pH 7, the critical E H above which soils consumed atmospheric CH 4 varied among the soils, but was generally >400 mV. Significant N 2 O production was observed between 200 and 500 mV. Nitrification could also contribute to N 2 O production when E H is >500 mV, a possible critical E H for the initiation of nitrification. The critical E H for substantial immobilization of Fe and Mn was estimated to be around 50 and 250 mV, respectively. The intermediate E H range (approximately −150 to 180 mV) provided optimum conditions for minimizing cumulative global warming potential resulting from CO 2 , CH 4 , and N 2 O production in soils. Our results have implications in interpreting the overall benefits of soil C sequestration efforts.