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Soil Science Society of America journal, 2004-07, Vol.68 (4), p.1342-1351
Ort / Verlag
Madison, WI: Soil Science Society of America
Erscheinungsjahr
2004
Quelle
Wiley-Blackwell Journals
Beschreibungen/Notizen
A better understanding of C turnover, with estimates of root‐derived C, is needed to manage soil C sequestration. The objective was to evaluate the long‐term treatment and environmental effects on unharvestable soil C components. Two N fertilizer treatments and a control were imposed during 29 yr of continuous corn (
Zea mays
L.) with stover removal as silage vs. stover return during grain harvest with moldboard plow (MB) tillage. Soil organic carbon (SOC) declined and natural
13
C abundance (δ
13
C) increased during the 29‐yr period. Field averages of SOC and δ
13
C (0–30 cm) were 96.4 Mg ha
−1
and −17.3‰ in 1965; respective values in 1995 were 78.9 Mg ha
−1
and −16.6‰. Loss of SOC was greater with stover removed or no fertilization, but δ
13
C increased for all treatments. Stover yield (SY), SOC, and δ
13
C data were applied to a model to estimate unharvestable C and predict total source C (SC) input from corn. The SC for 29 yr totaled 172 to 189 Mg ha
−1
when stover was harvested and 268 to 284 Mg ha
−1
when stover was returned. The SC input from unharvestable sources was 1.8 times more than SC from aboveground stover when N was added and 1.7 when N was not added. The root‐to‐shoot ratio was 1.1 when N was added and 1.2 with no N. Only 5.3% of the SC was retained as SOC. Unharvestable C contributions to rhizodeposition are much larger than suggested from controlled studies including C‐enriched CO
2
followed by soil respiration or CO
2
efflux measurements.