Database
The State Soil Bank of Minas Gerais (BSMG) is an entity created in 2010 in a contract between universities and the State Environmental Foundation of Minas Gerais. BSMG occupies a space of the Department of Soils of the Federal University of Viçosa, where it hosts more than 800 samples of soils collected in the state. BSMG further organizes and stores physical, chemical and geochemical analytical data from these soil samples.
Physical-chemical soil data:
The topsoil layer (0–20 cm in depth) was collected, equivalent to the A horizon for the majority of soils. Each sample is composed of five subsamples, collected in the form of a compass (North, South, East and West, all of them spaced apart by 3 m from one sample in the middle of the compass). Sampling was avoided in areas close to potential sources of contaminants (roads, railroads, urban and industrial developments, mining areas and pastures) and stainless steel equipment was used for collecting samples and sample preparation. Geostatistical tests indicate that the number of samples is sufficient to represent the pedological diversity of the state on a scale of 1: 650,000.
The soil samples were air-dried and passed through a stainless steel 10 mesh (2.0mm) sieve previous to analysis of texture and exchange capacity of soil. Soil pH was measured with a glass electrode in a 1:2.5 suspension of soil in deionized water. Exchangeable acidity (H+ + Al3+) was extracted in a solution of 1M ammonium acetate at pH 7. Exchangeable Ca+, Mg2+ and Al3+ were determined in a 1 M KCl solution. Exchangeable K+ and Na+ were extracted by the Mehlich-1 solution. From these results, the sum of the bases (SB) and the cation exchange capacity (CEC) were calculated for each sample. Extractable phosphorus (PM) was determined in a Mehlich 1 solution. Total soil organic matter (SOM) concentration was determined following the Walkley–Black method. The coarse sand, fine sand, silte and clay concentrations were determined by the sieve-pipette method, after dispersion with 0.1MNaOH.
Geochemical data:
The samples were crushed and sieved through a 200 mesh prior to acid digestion. Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sr, V and Zn concentrations were determined with an Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES) in five laboratories following the EPA 3051A digestion method. Satisfactory analyses (deviation below 20%) were obtained for the Montana I Soil and Montana II Soil standard reference materials using there analytical techniques. All Practical Quantification Limits calculated were lower than the Quality Reference Value for Minas Gerais soils.