Resumo

CABRERA, J. A  e  ZUAZNABAR, R. Impacto sobre el ambiente del monocultivo de la caña de azúcar con el uso de la quema para la cosecha y la fertilización nitrogenada. I. Balance del Carbono. cultrop [online]. 2010, vol.31, n.1, pp.00-00. ISSN 0258-5936.

Sugarcane monoculture with pre-harvest burning is a common practice in sugarcane-growing countries causing environmental degradation. In this regard, an investigation was carried out for 27 years, with the objective of defining the behavior of C content and balance in a sugarcane agro-ecosystem where burning is applied to harvesting. A long-term N level trial was conducted under drought conditions, with four planting cycles and 24 harvests. An eutric typical Red Ferralitic soil was used. Soil samples (0.00-0.30 m) were taken from each plot before planting and after some harvestings, besides determining its organic matter through Walkley & Black´s method. Soil organic C variation in time was fitted by means of Corg= a+bt1/2 equation. The total C input quantity per treatment was calculated according to the whole amount of above-ground biomass expressed in dry matter and C %. The entire C emitted to the atmosphere was estimated by taking into account soil organic C output and C emitted by dry leaf burning effect. The final C balance in the agro-ecosystem was calculated by adding to the total C released to the atmosphere the one that was exported with stalks from the field and subtracting the resulting annual C captured per treatment. Soil organic C decreased, even without applying mineral fertilizers (2.05 to 1.43 %). The applied N had no effect on soil organic C decrement. The total C lost from sugarcane agro-ecosystem, considering the one exported by stalks, was similar to that captured by the above-ground biomass; therefore, net balance tended to zero. As C fixed by sugarcane roots and stubble was not considered to estimate C balance, the net balance was positive towards the capture. In spite of the fact that soil fertility proved to be injured, the atmosphere was not contaminated by C concentration increment

Palavras-chave : sugarcane; monoculture; burning; agroecosystems; pollution; carbon; nitrogen fertilizers; soil fertility.

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