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Title: SOIL MICROBIAL BIOMASS, CARBON POOL, AND GREEN HOUSE GASES FLUXES IN A LONG TERM TILLAGE EXPERIMENT ON THE NORTH ATLANTIC COASTAL PLAIN

Author
item DE-POLLI, HELVECIO - EMBRAPA/LABEX
item Pizarro, Carolina
item COSER, THAIS - VOLUNTEER
item McCarty, Gregory
item Starr, James

Submitted to: BARC Poster Day
Publication Type: Abstract Only
Publication Acceptance Date: 3/15/2004
Publication Date: 6/15/2004
Citation: De-Polli, H., Pizarro, C.X., Coser, T., McCarty, G.W., Starr, J.L. 2004. Soil microbial biomass, carbon pool, and green house gases fluxes in a long term tillage experiment on the North Atlantic Coastal Plain [abstract]. Abs. 36. BARC Poster Day.

Interpretive Summary:

Technical Abstract: Soil microbial biomass (MB) plays an important role on the green house gases (GHG) budget. Considerable data are found in the literature on MB, but its relation with GHG dynamics is not consistently reported. Measurements of GHG and MB related attributes were performed in a long-term tillage experiment. The experiment used was under continuous culture of corn (Zea mays L.). Measurements were taken for soil density, total C and N, microbial biomass C (MBC) and N (MBN), MBCplus and MBNplus (without control subtraction), respiration, metabolic quotient (qCO2), qCO2plus, %MBC and %MBCplus in total C, and C stock. GHG measurements were performed throughout the year 2003 using an in situ static (non-steady-state) chamber technique with a ground fixed collar base. When comparing plow and no tillage treatments, soil density was higher for no tillage at all depths. No till had a higher total carbon stock (0-20cm) than plow till treatment (6% by volume equivalent and 10% by mass equivalent). On the other hand, C/N ratio was higher in no till at 0-2.5 but lower at 2.5-5.0 and 5-12.5cm depth. Levels for C, N, MBC, MBN, MBCplus, and MBNplus were much higher at the 0-2.5cm depth for no till with the difference between treatments decreasing at higher depths. qCO2 and qCO2plus values were similar at 0-2.5cm depth and higher for plow till in deeper layers. There was a tendency for plow till to show higher value than no till for %MBC/C and %MBCplus/C. In the case of GHG, CH4-C had the general tendency of emission for plow till and removal (soil uptake) for no till treatment throughout the year. Highest flux occurred in the winter when the difference between the two treatments was greatest. N2O-N had the general tendency of higher emission for no till than plow till treatment, but there were some exceptions, and the opposite occurred. Summer was the period when N2O-N emission was highest, although there were some points related to a short drought when the emission of N2O-N was as low as the winter period. For CO2-C emission, the difference between the two treatments was not significant in most cases, with the general tendency of low winter emissions increasing as summer approached and then decreasing through the rest of the year. Total global warming potential (GWP) for each gas was calculated using the ratio of CO2:CH4:N2O as 1:23:296. Plow tillage gave slightly higher carbon equivalent (Ceq) value than no tillage with a difference of 1.05 mg Ceq m-2 h-1 overall.