The researchers studied soil properties in Indian Dark Earth in the southern Amazonas region. They looked at the variability and spatial correlation of aggregates and carbon in the soil under coffee cultivation. By collecting samples at different depths and analyzing the data, they found that there was spatial dependence in the variables, with larger values observed at certain depths. They also discovered that the size of aggregates and bulk density were related to the amount of organic carbon in the soil, with some classes of aggregates showing negative correlation and others showing positive correlation with organic carbon.