ENZYME ACTIVITY AS AN INDICATOR OF SOIL QUALITY CHANGES IN DEGRADED CULTIVATED ACRISOLS IN THE MEXICAN TRANS-VOLCANIC BELT

Soils located at the Mexican Trans-Volcanic Belt (MTB) have a worrying degree of degradation due to inappropriate management practices. Early indicators of soil changes are very useful to alert about negative impacts of wrong managements on these volcanic soils. The aim of this work was to evaluate the short-term effects (4 years) of different agricultural practices on soil organic matter (SOM) quality and to validate the potential of the selected biochemical properties as optimal early indicators of soil quality in Mexican cultivated Acrisols. During 2002-2005 four agronomic management systems: conventional (Tc); improved conventional (Ti); organic (To) and fallow (Tf) were assayed in plots located at the MTB. An uncultivated soil under grass cover (Sg) was used as reference. Soil samples were collected at 0-10 cm depth and were analysed chemically (soil organic C, total N, water-soluble C and humic C), and biochemically (total and extra-cellular enzyme activity). After 4 years, soil organic C, total N, water-soluble C, and dehydrogenase activity had higher values in To, followed by Ti treatment. A similar response pattern was observed in the extra-cellular enzyme activity. The highest total enzyme activity was found in Sg, followed by Ti and To treatments, and the lowest values appeared in Tc and Tf. To and Ti increased SOM contents of the degraded Acrisols studied, while Tc and Tf managements decreased the quality of these soils. The results showed that the assayed soil enzymes can be used as indicators of quality changes of these Mexican volcanic soils. Copyright (C) 2010 John Wiley & Sons, Ltd.