Theme 04: Soil Fertility and Plant Nutrition
Description
The objective of this paper is to present the soil carbon (C) and nitrogen (N) dynamics in a chronosequence made of a forest and pastures of different ages established in a Oxisol in the Western Brazilian Amazon Basin. The results of soil Carbon and Nitrogen stocks and gases fluxes were discussed. Stable 13C isotopic technique was used to calculate for a determinate age of pasture installation, the proportion of soil C remaining from the forest system and the proportion of soil C introduced by the grasses of the pasture system. The C lost from the original pool under the forest is 1.0 to 1.6 kg C m-2 concentrated during the first 5 years as pasture, and that the C fixed by the pasture (net fixation) is 1.7 to 2.3 kg C m-2 for the total period of 35 years. We agree with the assumption that cattle ranching would never be a profit-making venture as long as only the revenue from the sale of cattle is taken into account. But, now a days, the notions of taxes or refunds for C sequestration and land rehabilitation turn the management of areas that have already been converted to pasture a strategy for C sequestration.
Included in
Soil Carbon and Nitrogen Dynamics After Pasture Installation in the Amazon Region
The objective of this paper is to present the soil carbon (C) and nitrogen (N) dynamics in a chronosequence made of a forest and pastures of different ages established in a Oxisol in the Western Brazilian Amazon Basin. The results of soil Carbon and Nitrogen stocks and gases fluxes were discussed. Stable 13C isotopic technique was used to calculate for a determinate age of pasture installation, the proportion of soil C remaining from the forest system and the proportion of soil C introduced by the grasses of the pasture system. The C lost from the original pool under the forest is 1.0 to 1.6 kg C m-2 concentrated during the first 5 years as pasture, and that the C fixed by the pasture (net fixation) is 1.7 to 2.3 kg C m-2 for the total period of 35 years. We agree with the assumption that cattle ranching would never be a profit-making venture as long as only the revenue from the sale of cattle is taken into account. But, now a days, the notions of taxes or refunds for C sequestration and land rehabilitation turn the management of areas that have already been converted to pasture a strategy for C sequestration.
