Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8487957 | Agriculture, Ecosystems & Environment | 2014 | 14 Pages |
Abstract
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 mâ2 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 mâ2 yrâ1) and C pools (+0.52 to 0.90 kg C mâ2 yrâ1) 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 C mâ2 yrâ1 (in grassland soils) to 0.71 kg C mâ2 yrâ1 (in cropland under no tillage). The carbon pool declined during the third year at rates of 0.41 kg C mâ2 yrâ1 (cropland under disk tillage) to 0.76 kg C mâ2 yrâ1 (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.
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Authors
Anne-Sophie Perrin, Kenji Fujisaki, Caroline Petitjean, Max Sarrazin, Mathieu Godet, Bernard Garric, Jean-Claude Horth, Luiz Carlos Balbino, Austrelino Silveira Filho, Pedro Luiz Oliveira de Almeida Machado, Michel Brossard,