Perrin A. S. auteur aut IRD Fujisaki Kenji auteur aut IRD Petitjean C. auteur aut IRD Sarrazin Max auteur aut IRD Godet M. auteur aut IRD Garric B. auteur aut IRD Horth J. C. auteur aut IRD Balbino L. C. auteur aut IRD Silveira A. auteur aut IRD Machado Plod auteur aut IRD Brossard Michel auteur aut IRD text journalArticle eng text/pdf born digital access Fire-free forest conversion with organic inputs as an alternative to slash-and-burn could improve agro-ecosystem sustainability. We assessed soil carbon mass changes in a sandy-clayey and well-drained soil in French Guiana after forest clearing by the chop-and-mulch method and crop establishment. At the experimental site of Combi, native forest was cut down in October 2008; woody biomass was chopped and incorporated into the top 20 cm of soil. After about one year of legume and grass cover, three forms of land management were compared: grassland (Urochloa ruziziensis), maize/soybean crop rotation with disk tillage and in direct seeding without tillage. There were four replicates. We measured 14.16 kg m(-2) of carbon in 2 mm-sieved soil down to 2 m depth for the initial forest. Forest clearing did not induce significant soil compaction; neither did any specific agricultural practice. In converted soils, C stocks were measured in the 0-30 cm layer after each crop for three years. Carbon mass changes for soil fractions <2 mm (soil C stock) and >2 mm (soil C pool) in the 0-5, 5-10, 10-20 and 20-30 cm soil layers were assessed on an equivalent soil mass basis. One year and 1.5 years after deforestation, higher C stocks (+0.64 to 1.16 kg C m(-2) yr(-1)) and C pools (+0.52 to 0.90 kg C m(-2) yr(-1)) were measured in converted soils, compared to those of the forest into the top 30 cm of soil. However, the masses of carbon in these converted soils declined later. The highest rates of carbon decrease were measured between 1.5 and 2 years after forest conversion in the <2 mm soil fraction, from 0.46 kg Cm-2 yr(-1) (in grassland soils) to 0.71 kg C m(-2) yr(-1) (in cropland under no tillage). The carbon pool declined during the third year at rates of 0.41 kg C m(-2) yr(-1) (cropland under disk tillage) to 0.76 kg C m(-2) yr(-1) (grassland soils). Three years after forest conversion, C masses in the top 30 cm of soils for grassland showed similar values than for forest. In comparison, the carbon stock in cropped soils managed under no tillage in direct seeding (without mulch) was significantly 17% and 16% lower than in forest and grassland soils, respectively. None of the studied agricultural practices succeeded in accumulating carbon from the chopped forest biomass. specialized French Guiana Fire-free Deforestation Annual crops Brachiaria No-tillage GUYANE FRANCAISE 068 076 082 184 101-114 2014 0167-8809 https://www.documentation.ird.fr/hor/fdi:010061911 10.1016/j.agee.2013.11.009 0167-8809 [F B010061911] https://www.documentation.ird.fr/hor/fdi:010061911 https://www.documentation.ird.fr/intranet/publi/2014/05/010061911.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2014-05-28 2017-08-23 fdi:010061911 fre