Dynamics of organic carbon in soils of the pastures in Brazilian Amazon basin. [Portuguese

• Published in: Revista INIA de Investigaciones Agronomicas Vol. 1
• Main Authors: Cerri C.C, Moraes J.F.L. de, Volkoff B
• Format: Journal Article
• Language: Portuguese
• Published: 1992
• Subjects: amazonia; amazonie; brasil; brazil; bresil; carbon; carbone; carbono; pastizales; pastures; paturages; propiedades fisico quimicas suelo; propriete physicochimique du sol; soil; soil chemicophysical properties; sol; suelo
• ISSN: 0797-5481

The actual use of soils in the Amazon basin is now the substitution of natural vegetation (Floresta tropical amazonica) by sown pastures. This paper analyses the dynamics of organic carbon in the upper 20 cm of soil, after different periods of pasture establisment, taking as a reference the content under forest. Three areas with soils of different clay content were selected, Oxisol of Manaus (77 clay), Alfisols and Ultisols of Rondonia (24 and 13 clay, respectively). The initial soil carbon under forest was: 90 x 10 6g C/ha for Oxisols, 48 x 10 6g C/ha for Afisols and 29 x 10 6g C/ha for Ultisols. After clearance and pasture establishment, the carbon content varied according to soil type and time of cultivation. During the first four years the carbon content of Oxisols decreased but afterwards an increment was observed and in the seventh year it surpassed the initial level. The same occurred in the Alfisols, but the minimum content was attained in the eleventh year, and the value was re-established after twenty years of cultivation. A different evolution was observed in Ultisols where carbon content was always above that of the original forest. It studied was the use of isotopic techniques with Carbon-13 for quantification of losses of native forest carbon and inputs due to pastures.