EVALUATION OF CHANGES OF MICRO-AGGREGATION IN DETERIORATED VOLCANIC SOILS BY USING AMENDMENTS IN THE BASIN OF MEXICO

The southern portion of the Basin of Mexico, an area where volcanic soils are dominant, has been intensively used for agricultural activities since pre-hispanic times. This intensive use has provoked erosion, loses of organic matter and changes in soil structure. Nowadays, farmers cultivated corn, oat, amaranth and Opuntia (nopalitos). They must add a high amount of fertilizers and manures. In this work, we evaluated the changes in the soil micro-aggregation using several amendments, mainly based on the residues of the Opuntia production and compare to the structure observed in non-agriculture soils (preserved) and non-treated soils. The analyzed amendments were: bovine manure, Opuntia mucilage and compost. The analysis was done in a greenhouse using 1 kg pots. We add 1 kg-soil and 10 g- amendment, with oat seeds, and leave for 3 months. During this time, the pots were frequently irrigated. After the experiment, unaltered samples were taken, which were impregnated with a polyester resin in order to obtain thin sections for micromorphological and morphometric studies. The samples from the less perturbed areas showed granular aggregates, typical for andic soils, while the areas with intensive agriculture have soils where the aggregation is very week. The experiments showed an efficient aggregation caused by the Opuntia mucilage and the manure.