Soil quality of cultivated and native pastures systems in the Nhecolandia sub-region, South Pantanal Wetlands. / Qualidade do solo em sistemas de pastagens cultivada e nativa na sub-regiÃo da NhecolÃndia, Pantanal Sul Mato-Grossense

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

The Pantanal is one of the planetâs largest continuous wetlands areas and where fauna and flora of outstanding beauty and abundance develops. Favored by the richness of natural resources, beef cattle raising, conducted in extensive raising systems, constitutes the chief economic activity. However, the search for yield increases and greater competitivity of this cattle raising has lead to land clearing for cultivated pasture establishment, raising concerns about the sustainability of the Pantanal production systems. The objective of this work was to evaluate the soil quality of cultivated and native pastures systems in the Pantanal Wetlands in order to constitute a tool which can aid in the monitoring of its sustainability. In view of this, two independent studies were conducted: one in which the interrelationships among soil, flooding regime and landscape units in the Nhecolandia sub-region were evaluated, aiming to assist the sustainable management of native pasture of the Pantanal Wetland; and the other in which the alterations in soil chemical, physical and biological attributes of cultivated pasture in replacement of the native forest and in native pasture submitted to the continuous grazing system were evaluated, generating two indexes for the estimation of soil quality. From the planialtimetric survey of a 151 ha area, situated on a farm characteristic of the Nhecolandia sub-region, the physical and chemical attributes of the landscape units subject to different flooding regimes were evaluated, as follows: flood free (FF) â semideciduous forest and forested savannah; subject to occasional floodings (OF) â arboreal savannah and open grasslands with predominance of Elyonurus muticus; subject to periodical floodings (PF) - open grasslands with predominance of Axonopus purpusii and Andropogon spp, edge of ponds and temporary channels and lowlands. In native forest environments, Brachiaria decumbens cultivated pastures of different formation ages established in replacement of the native forests and native pasture under a continuous grazing system, without grazing for 3 years and without any grazing for 19 years (ecological reserve), also located on Nhecolandia farms, the chemical, physical and biological attributes of soil were evaluated and two soil quality indexes (SQI1 and SQI2) were generated. SQI1 was calculated from the deviations of the soil attributes of the cultivated and native pastures systems relative to the respective natural environments (reference); and SQI 2 was calculated from an additive model which considers the main soil functions and the quality indicators associated to them, weights being ascribed both to the functions and to the indicators. The predominant soil in the landscapes units is Quartzarenic Neosol (Entisol), with a hydromorphic character in the units subject to periodic floodings. With the exception of the semideciduous forest, the other landscape units presented very poor natural soil fertility. The units subject to occasional and periodic flooding were more susceptible to degradation of the physical attributes, possibly due to the more intense animal traffic. The interrelationships among soil, flooding regime and landscape units suggest that the occurrence and extent of the landscape units should be considered in the establishment of native grassland sustainable management strategies. The integrated analysis of the chemical, physical and biological attributes of soil of different environments of the Pantanal Wetlands gave evidence that the cultivated and native pastures systems promoted a significant reduction of soil quality, the most notable reductions being evidenced by the replacement of the native forest by cultivated pasture. The two soil quality indexes generated were effective in reflecting the variation of soil quality in the different Pantanal environments. Therefore, they are capable of being adopted in the sustainability monitoring of the production systems.

ASSUNTO(S)

environmental conservation, sustainability, soil fertility, organic matter ciencia do solo sustentabilidade, conservaÃÃo ambiental, fertilidade do solo, matÃria orgÃnica

ACESSO AO ARTIGO

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