02404naa a2200229 a 450000100080000000500110000800800410001902400330006010000160009324501390010926000090024852017110025765300190196865300240198765300130201165300130202470000190203770000130205670000170206970000180208677300700210410494772019-10-28       2007    bl uuuu     u00u1 u    #d7 a10.2134/agronj2006.03172DOI1 aQUINCKE, A.  aOccasional tillage of no-till systemsbCarbon dioxide flux and changes in total and labile soil organic carbon.h[electronic resource]  c2007  aABSTRACT: Soil organic carbon (SOC) accumulation occurs mostly in the top 5 cm of soil with continuous no-till (NT) while SOC losses often occur atdeeperdepths.Wehypothesizethatone-timetillageconductedonce in .10 yr to mix the high SOC surface layer with deeper soil will not result in large SOC losses following tillage with a net positive gain in SOCeventually.Twoexperimentsinlong-termNTfieldswereinstalled under rainfed corn (Zea mays L.) or sorghum [Sorghum bicolor (L.) Moench.] rotated with soybean [Glycine max (L.) Merr.] in eastern Nebraska. Tillage treatments were applied in the spring or fall and included: NT, disk, chisel with 10-cm wide twisted shanks, moldboard plow (MP), and mini-moldboard plow (miniMP). A portable infrared gas analyzer was used to monitor CO2 flux immediately following tillage. Effect of tillage on profile distribution of total and labile (particulate and oxidizable) SOC was determined. At 24 to 32 mo following tillage, SOC mass was determined for depths of 0 to 5, 5 to 20, and 20 to 30 cm. Some tillage operations effectively redistributed total and labile SOC with little increase in CO2 flux compared with NT. TotalandlabileSOCconcentrationswerereducedby24to88%inthe 0- to 2.5-cm depth and increased by 13 to 381% for the 5- to 10-cm depth for the various tillage operations. Moldboard plowing caused the greatest redistribution of SOC. On an equivalent soil mass basis, tillage did not cause significant losses of total or labile SOC between tillage and planting of the next crop or by 24 to 32 mo after tillage. Stratification of SOC in long-term NT soil could be reduced most effectively by means of one-time MP tillage without increased loss of labile SOC.  aCARBON DIOXIDE  aSOIL MICROORGANISMS  aSOYBEANS  aZEA MAYS1 aWORTMANN, C.S.1 aMAMO, M.1 aFRANTI, T.G.1 aDRIJBER, R.A.  tAgronomy Journal, July 2007, Volume 99, Issue 4, Pages 1158-1168.