Abstract
ABSTRACT The proper soil use and management are essential for a sustainable production, thus the pursuit for systems that minimize damages to the environment and improve soil fertility is continuous. The objective of this study was to evaluate changes in soil fertility by the use and management of an Oxisol (Latossolo Vermelho-amarelo, SiBCS) in the Amazon biome. The soil uses and management systems evaluated were native forest, native pasture, minimum tillage system and conventional tillage system. The chemical atributes of the soil layers 0.00-0.10, 0.10-0.20, 0.20-0.30 and 0.30-0.40 m were evaluated. The soil pH (CaCl2) and the contents of organic matter, available phosphorus and exchangeable potassium, calcium, magnesium and aluminum were evaluated and the saturation by Al, effective cation exchange capacity and soil potential were determined. The highest pH values were found in the native pasture area, and the highest exchangeable aluminum contents were found in the layers 0.00-0.10 and 0.10-0.20 m of the conventional tillage system. The highest phosphorus availability was found in the layer 0.00-0.10 m of the native forest area. The highest potassium availability was found in the minimum tillage system. The lowest calcium and magnesium values were found in the layers 0.00-0.10 and 0.10-0.20 m of the conventional tillage system. The highest soil organic matter content was found in the layer 0.00-0.10 m of the native forest area. The nutrient availability for plants decreases in soils managed using the conventional tillage system. Soil uses and management systems of little soil disturbance are recommended to minimize environmental degradation in the Amazon biome.
Highlights
Seventy-two million hectares of the Brazilian Amazon biome was deforested in recent decades, of which fifty-six millions are converted into pastures and more than half are in advanced degradation state (DE SOUZA BRAZ; FERNANDEZ; ALLEONI, 2013; SILVA NETO et al, 2012), due mainly to inadequate soil and crop managements
Bayer and Bertol (1999) found no significant difference in soil pH depending on the management systems
The results found in the present work confirm those found by Lourente et al (2011), who found similar potassium availability in native forest and native pasture areas, and by Bayer and Bertol (1999), who found higher potassium availability in a minimum tillage compared with a conventional tillage system
Summary
Seventy-two million hectares of the Brazilian Amazon biome was deforested in recent decades, of which fifty-six millions are converted into pastures and more than half are in advanced degradation state (DE SOUZA BRAZ; FERNANDEZ; ALLEONI, 2013; SILVA NETO et al, 2012), due mainly to inadequate soil and crop managements. Inadequate soil managements potentially contribute to environmental degradation, since it negatively changes the soil physical, chemical and biological characteristics (SILVA NETO et al, 2011). This processes are even more serious in the Amazon region, in which the conversion into pastures occurs often after the use of burning practices (TOWNSEND; COSTA; PEREIRA, 2010) and soil tilling by plowing and harrowing, causing destruction of aggregates, decrease of organic matter content in the soil surface layers and increase of water erosion (BAYER; BERTOL, 1999; MOREIRA; MALAVOLTA, 2004; SATO et al, 2012). Santos et al (2008) reported the use of conservationist systems (no-tillage and minimum tillage) resulting in better soil fertility than the conventional system after 20 years of use
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