Resumo

FREGOSO TIRADO, Luis E.. Changes in Chemical and Microbiological Characteristics of a Vertisol Induced by Conservation Tillage Systems. Terra Latinoam [online]. 2008, vol.26, n.2, pp.161-170. ISSN 2395-8030.

In the region of El Bajio (Central Mexico), conventional tillage (burning crop residues + crossed tandem disking + bedding) is degrading the quality of Vertisols, which has brought about serious environmental, economic and social consequences. The objective of this study was to assess the short-term effects (2.5 years, five growing cycles) of no-tillage (NT) systems associated with two crop residue management alternatives (partial removal through baling versus full retention) and the conventional tillage system on the quality of a Vertisol evaluated by means of chemical and microbiological indicators. Results showed that microbiological indicators were more sensitive to the evaluated management systems than chemical indicators. The content of soil microbial biomass carbon (0-15 cm) increased between 16 and 24%, whereas soil microbial biomass nitrogen increased 18% with conservation tillage systems relative to those of the conventional system. The largest changes were found in the 0-5 cm soil layer, which reflected an improvement in soil quality under NT. The detrimental effect originated by partial removal of crop residues on the soil microbial activity indicators was evident until the fifth growing season. Soil under NT was moderately acidified (pH = 5.4) in comparison with the soil under conventional tillage (pH = 6.2). Baling crop residues associated with no-tillage is a good strategy to facilitate adoption of NT since it reduces a factor of excess of residues that growers fear. It also makes the use of residues for forage and for soil cover compatible with its protection and improvement.

Palavras-chave : baling crop residues; soil microbial biomass carbon and nitrogen; El Bajio.

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