Soil Characteristics in an Area Under Influence of Dumping Holes Used for Infiltration/Percolation of Wastewater Discharged from Coffee Grain Processing.

In the south of the Espirito Santo State, Brazil, the wastewater generated in the coffee grain processing (CGPW) is disposed by the farmers in dumping holes in the soil. This practice has the advantages of the requirement of small areas, the low costs, and the feasibility of construction, operation and management. However, it has to be appropriately executed in order to avoid the contamination of the underground water and the occurrence of changes in the soil chemical and physical characteristics. It was made the characterization of the disposed CGPW and determined the chemical and physical characteristics in soil samples collected near the dumping holes used for CGPW disposal in counties from the Espírito Santo State. The samples were collected at distances up to 5 in the lateral of the hole, at different depths and in the bottom of the dumping hole. The disposed CGPW presented salinity, acid pH, high concentration of total solids and high organic content, with the element N being the most concentrated. The exchangeable K increased in almost all soil samples collected in the lateral positions. This caused a higher electrical conductivity in the saturation extract, a higher percentage of dispersed clay in the soil, mainly in the samples closer to the dumping hole, a decrease in the potential acidity, and changes in the pH of some samples. The soil exchangeable Ca and Mg also increased in the samples closer to the dumping holes with increase of the sum of bases and index of base saturation. The available P decreased in the samples more distant from to the dumping holes. There was no detection of  Na in the samples and no variation of exchangeable Al concentration, but the Al saturation index decreased closer to the dumping hole. The cation exchangeable capacity (CEC), at pH 7, decreased in most of the samples whereas the effective CEC increased in the samples closer to the dumping holes. The organic matter content and the remaining P increased in some samples located at 50 cm from the dumping holes. In the soil samples collected at the bottom of  the holes, the pH, the Mg concentration, the sum of bases and índex of base saturation decreased whereas the electrical conductivity, clay disperse in water, organic matter content, moisture equivalent, potential acidity, Al saturation and CEC, at pH 7, increased. There was increase also in the available P, remaining P, and exchangeable Ca and Al. The exchangeable K and the effective CEC did not show variation in the samples collected in different depths at the bottom of the hole.