Abstract

SANZANO, Gerardo Agustín; CORBELLA, Roberto Daniel; GARCIA, José Ramón  and  FADDA, Guillermo Salvador. Physical and chemical degradation of a typic Haplustoll under different management systems. Cienc. suelo [online]. 2005, vol.23, n.1, pp.93-100. ISSN 1850-2067.

In the province of Tucumán there was a great process of expansion of the farming borders to dry sub humid and semi-arid areas. This process led to the physical, chemical and biological degradation of the soils. The objective of this work was to determine the long term effects of different tillage systems on physical and chemical degradation of a Typic Haplustoll and its relationship with hydraulic properties related to water storage. In a tillage experiment established 20 years ago soybean under no till and conventional tillage, gramineous pastures (P) and natural forest (MN), the following properties were studied: organic carbon (CO), extractable phosphorous (Pe), cationic exchange capacity (CIC), pH, bulk density (DA), structural stability (EE), hydraulic conductivity (Ksat), basic infiltration (Ibas) and pores greater than 0,25 mm. There were significative differences in CO and CIC between LC and treatments P and SD, but also between P and SD with MN. Pe contents were 28, 16 and 14 % for SD, P and LC respectively in relation to MN. Soil pH was not affected by the different tillage systems. The structural stability was the property that appeared to be more sensitive to the soil tillage in a decreasing sequence from the natural forest to the conventional tillage, that represents the greatest level of physical degradation among the studied situations. This variable was strongly associated to the organic carbon except in the soil pasture, where the physical effect of the roots was much more important that the soil organic matter content. The basic infiltration in soils with no till and pastures was significantly higher than in conventional tillage even though in the three systems it was inferior to the values of the natural forest. Basic infiltration, hydraulic conductivity and macroporosity showed the low level of recuperation of the studied soils. However, due to the subhumid dry and semi- arid nature of the region, the difference in the values of infiltration between the soils with no till and pastures in relation to conventional tillage showed that the implementation of conservationist practices can increase the water storage that is a key variable to the appropriate crop development.

Keywords : No tillage; Soybean; Physical degradation; Management.

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