Characterization of subsoil compaction in a "Tabuleiro" area on Curado experiment station in Recife

Abstract

Analytical results are shown for 9 samples each of 8 cm in thickness in a soil located in the "tabuleiro" area of the Curado Experiment Station. The purpose of the study was to determine which physical, chemical and microbiological measurements could be used to characterize compaction in the soil profile. The study showed that only certain laboratory methods are suitable for characterizing soil compaction. These are: permeability coefficient, macro and micro porosity, apparent specific weight, percentage of saturation, direct observation of root penetration and total porosity. Useful supplementary determinations are mechanical analysis (total and natural dispersion of clays), organic matter, exchange complex and ki and kr. Laboratory determinations that were not helpful in characterizing compaction were: actual specific weight, moisture equivalent, moisture at 15 atmosphere, phosphorus and nitrogen. Data obtained in morphological, physical, chemical and microbiological studies indicated that soil compaction is a consequence of obstruction of a part of the macropores with organic and mineral coloidal material which causes modifications in the physical properties of subsoil layers. Conditions of climate, topography and the nature of clays appear to contribute to the formation of the compacted layers. The destruction of compaction through agricultural practices should improve the physical condition of the soil, facilitate the penetration of plant roots and increase the productive capacity of the soil.