02606naa a2200445 a 450000100080000000500110000800800410001910000250006024501370008526000090022252013900023165000090162165000180163065000180164865000150166665000090168165000240169065000240171465000170173865000100175565000120176565000230177765000100180065000190181065000250182965000090185465000200186365000100188365300110189365300190190465300170192370000230194070000260196370000240198970000170201370000190203070000170204970000180206677300760208415740982022-05-17       2009    bl uuuu     u00u1 u    #d1 aMACHADO, P. L. O. A.  aCarbon stocks of a Rhodic Ferralsol under no-tillage in Southern Brazilbspatial variability at a farm scale.h[electronic resource]  c2009  aThe objective of this study was to determine, at a farm level, the spatial variability of organic carbon stock (CS) at different depths on a field of 1 soil type in long-term (13-year) crop production under no-tillage. The crop rotation comprised soybean [Glycine max (L.) Merr.] alternating with maize (Zea mays L.) in the summer season. For the winter season, wheat (Triticum aestivum L.) was cropped in rotation with black oat (Avena sativa L.), a cover crop. The 12.5-ha field was sampled at a density of 6.25 samples/ha. Within the coarse grid, 2 dense grids with 20-, 10-, and 5-m spacing were established. Soil samples were collected at all grid nodes and analysed for soil organic carbon and bulk density. The CS at 0-0.05, 0.05-0.10, and 0.10-0.20m was corrected for equal soil mass. Geostatistics was used for the estimation of spatial distribution of CS at 3 soil depths. We found that CS variation was low to medium (CV 6.7-19.4%). The variograms of CS at all depths were best fitted by spherical models and showed ranges of 120m, except at 0-0.05m (range 109m). At 0-0.20m depth, CS was 15.2-24.5t/ha (CV 8.2%, range 120m). The use of geostatistics reveals a powerful tool for the spatial estimation of CS at depth of a Rhodic Ferralsol under no-tillage, and demonstrated CS variation on a 12.5-ha area, even though soil and crop management were the same for &gt10 years..  aCorn  acrop rotation  ageostatistics  aNo-tillage  asoil  aSoil organic carbon  aSoil organic matter  asoil texture  aWheat  aCarbono  aMatéria orgânica  aMilho  aPlantio direto  aRotação de cultura  aSolo  aTextura do solo  aTrigo  aBrasil  aOrganic carbon  aSoil organic1 aBERNARDI, A. C. C.1 aORTIZ VALENCIA, L. I.1 aMEIRELLES, M. S. P.1 aSILVA, C. A.1 aGIMENEZ, L. M.1 aMOLIN, J. P.1 aMADARI, B. E.  tAustralian Journal of Soil Researchgv. 47, n. 3, p. 253-260, May 2009.