Effects of no-till duration on the methane oxidation capacity of Alfisols.

摘要

Frequent tillage negatively affects the methane (CH4) oxidation capacity of agricultural soils. The restoration of that capacity of soils through no-tillage (NT) adoption has been suggested, but is not well documented. With the expectation of increased CH4 oxidation with longer NT duration, a tillage chronosequence study was conducted at paired sites in Ohio under conventional tillage (or plow till, PT) and NT for 9, 13, 36, and 48 years. Nearby deciduous forests were also included to estimate the maximum oxidation capacity of undisturbed local soils. Surface soil samples (0-5, 5-10, 10-20, 20-30 cm) were collected in April (soil moisture 29) and in August 2010 (moisture 19), sieved (6.3 mm), and incubated (initial CH4 5 micro l L-1) to determine the CH4 oxidation capacity. The results showed a significant effect of tillage practice on CH4 oxidation. With the exception of the site under NT for 9 years, the CH4 oxidation rates were consistently higher (2-40 times) in NT than in PT soils during both the April and August sampling dates. A similar effect of NT was also observed when incubation was conducted with intact soil cores, but the rates were lower, perhaps due to restriction of CH4 diffusion in the cores. Across the sampling dates and depth, the CH4 oxidation capacity increased linearly with NT duration averaging 3.2, 4.2, 11.5, and 13.6 micro g CH4-C kg-1 soil day-1 at sites under NT for 9, 13, 36, and 48 years, respectively. While the CH4 oxidation rate in PT soil was 10-12 of the level in the forest soils, it was 36-37 at sites under NT for >30 years. These results demonstrate the positive effect of NT on the CH4 oxidation in soils and the potential impact of continued NT maintenance on the CH4 sink strength of agricultural soils.