Dehydrogenase and mycorrhizal colonization: Tools for monitoring agrosystem soil quality

In order to improve food production while reducing environmental impact, the redesign of agrosystems to incorporate monitoring tools for decision-making is a fundamental requirement. Chemical and physical indicators of medium and long-term soil quality have been developed in order to monitor changes in agroecosystems; however, it is crucial to develop parameters that can predict the short-term trajectory of the system. For this reason, the objective of the present study was to determine whether certain soil biological parameters, such as the activities of microbial enzymes (dehydrogenase (DH), acid phosphatase (ACP), urease (URE) and protease (PRO)) and mycorrhizal colonization, could be useful as indicators of soil biological quality, given their sensitivity to different agricultural management practices. An evaluation was conducted over two years in five different agrosystems of Valle de México in Mexico. The activity of DH presented greater sensitivity to changes in agricultural management produced by types of tillage and input (organic or synthetic) and topological arrangement, compared to that of URE, ACP and PRO, which did not present a clear pattern with respect to the different agrosystems or to sampling date (based on the agricultural practices). Mycorrhizal colonization was sensitive to the type of inputs used, but not to tillage type or crop rotation. It is therefore considered that DH and mycorrhizal colonization could represent useful parameters for measuring soil quality and the environmental impact of the use of agrochemicals in agriculturally managed soils. Based on DH and mycorrhization, the agrosystem with the highest quality soil was the Mesoamerican system known as “Milpa” (typified by minimum tillage, intercropping and organic inputs).