Protocol 18 - Soils

Coordinator:
Dra. Maria de Lourdes Ruivo (MPEG) • E-mail: ruivo@museu-goeldi.br
Protocol researchers:
Mato Grosso - Dr. Marco Antonio Camillo de Carvalho (UNEMAT/AF)
Amapá - Dr. Marcelino Carneiro Guedes (IEPA)
Maranhão - Dr. Alessandro Costa da Silva (UEMA)

Pedology is the part of soil science that looks at the genesis, morphology, distribution, mapping, taxonomy and classification of soils. The importance of soil studies is in providing information that enables us to better understand environmental dynamics. The utilized soil protocol methodology is based on the Brazilian System of Soil Classification (EMBRAPA, 1999), through the identification and definition of surface and subsurface diagnostic horizons (determined by observing diagnostic attributes), initially recognized in the field and subsequently sampled and analyzed at the laboratory.

Profile description, observations and sampling of the soil:

The soil profile description and the sample collections are, as a preference, carried out through the opening up of 1.50 m depth, minimum, by 1 m width trenches (or until soil horizon B is identified) within each pedology unit and/or representative unit area, supplemented by the use of Dutch augers as and when necessary, for an appropriate understanding of the vertical and lateral pedological variation at the site. In the specific case of PPBio grids where various biological studies as well as other studies of an environmental nature are carried out, it isn’t advisable to excessively modify the soil and vegetation, whether part of the understory or not; it being essential to carry out work with an auger. For a good understanding of the lateral and vertical variation of the soil, including a number of boreholes in the subplots, it is very important to look outside of the grid where similar units to those found within the grid can be compared, opening the trenches and describing the diagnostic horizons in detail, adequately sampling them for routine laboratory analyses that can then facilitate identification of the pedogenetic units.

The morphological description of the soil profiles in the PPBio plot will be carried out with the aid of the ‘Manual of Soil Description and Collection in the Field’ (LEMOS; SANTOS, 2002), using the “recognition of medium intensity” level of detail. After identification and separation of the pedogenetic horizons or layers in the field, samples are collected for evaluating the textural, availability and chemical characteristics of the soil cover within the experimental area. Sample coloring is ascertained by comparison with the Munsell colour chart (1975).

Preparation and analysis of samples:

After being collected and dried in the air, the soil samples are then sifted through a 2 mm mesh-size sieve, resulting in fine air-dried soil (FADS), from which the physical and chemical analyses can then be carried out, as recommended in the Embrapa System Manual of Analytical Methods (1997).

Determination of particle size:

The pipette method will be used for particle size analysis (total dispersion), a principle based on the speed at which soil particles fall, by determining the time for vertical displacement after suspension of the soil in water, utilizing a chemical dispersant, pipetting a volume of the suspended soil for subsequent determination of the amount of clay through drying in an oven. Any coarse material (fine and coarse sand) must be separated by sieving, dried in ovens and then weighed to obtain the respective percentages.

Chemical determinations

The soil samples will be submitted for chemical analyses (pH, exchangeable cations, organic carbon, soil moisture and organic nitrogen), in accordance with manual methods of Embrapa soil analysis (1997). The pH values in H2O and KC1 N are measured by glass electrode, suspended in a 1:2.5 soil-liquid ratio; exchangeable cations Ca+++ and Mg++ with KC1 and determined by atomic absorption spectrometry (AAS); K+ and Na+ extracted with HC1 0.05N at a 1:10 soil-solution ratio (by not using the Mehlich-1 extraction solution) and determined by flame photometry; acid-extractable including A1+++ extracted with KC1 N and titrated with NaOH 0.025N, and bromothymol blue indicator and hydrogen and aluminium extracted with Ca(OAC)2 N to pH 7.0 and triturated with NaOH phenolphthalein indicator, the hydrogen being calculated by difference; available phosphorous, extracted with HC1 0.05N + H2S04 0.025N and determined by calorimetry; organic carbon by oxidation in wet medium, with K2Cr2O7 0.4N and triturated by Fe(NH4) 2.6H20 0.1N and diphenylamine indicator; total nitrogen by digestion with acid mixture, diffusion and titration of NH3 with NC1 and H2SO4 0.01N. Both can also be determined by elemental analyzer.

Micromorphology analysis

The scanning electron microscope process is equally used for both basic and applied research. This technique allows different types of materials to be observed and characterized, such as: mineral, vegetable, animal and agri-food products, it being possible to characterize these materials in terms of their morphology, organization and chemical composition. Micromorphology analysis is a very good mineralogical composition indicator, in addition to measuring the porosity and aggregation between the particles that form soil.

The micromorphology observations and EDS analyses (indirect assessment of mineralogy) can be carried out on soil aggregates or on thin layers, in this particular case, obtained from undisturbed soil samples, and observed through a Scanning Electron Microscope at the laboratory of the Emílio Goeldi Museum. After routine preparation, the samples are dried in an oven, with the grains of soil being mounted on 10 mm diameter aluminium supports. In order to become conductive, the supports are then metallized with Au for 2'30”, depositing a layer of 12 nm, on average, onto the sample. 15 KV voltage acceleration will be used in order to obtain images, either by using a secondary electron detector or through backscattered electron images. Interpretation of micromorphology in grains of soil is carried out according to the Kemp (1985), Davidson and Carter (1998) and the Ruivo et al. (2003) methodologies.

 

Training and capacity building

PPBio training is essential for the success of the program. Training consists of short-term courses held at the Regional Centers for the training of students and professionals alike, or even for technicians from partner organizations.

Training involves: target group collection and identification techniques; training on how to establish research sites; training on the collection of basic and biological protocol information; training on the use of database technology; training on the use of the SINBIO inventory program; collection curator training; training on the use of statistical packages for the analysis of data; and training in collection management programs.

Referências

DAVIDSON, D.A.; CARTER, S.P. Micromorphology evidence of past agricultural pratices in cultivated soils :the impact of a traditional agricultural system on soils in papa stour, Shetland. Journal of Archaeological Science, v. 25,n. 9, p. 827-838, 1998.

EMBRAPA-Centro Nacional de Pesquisa de solos. Sistema brasileiro de classificação de solos. Rio de Janeiro: Embrapa Solos, 1999. 412p.

EMBRAPA-Serviço Nacional de Levantamento e Conservação de Solo. Manual de métodos de análise de solo. Rio de Janeiro: Embrapa Solos, 1997. 212p.

KEMP, R. A. Soil micromorphology and the quaternary. Cambridge: Quaternary Research Association, 1985. (Technical Guide n. 2).

LEMOS, R.C.; SANTOS, R.D. Manual de descrição e coleta de solo no campo. 4. ed. Viçosa: SBCS, 2002. 83p.

MUNSELL COLORS COMPANY. Munsell soil colors charts. Baltimore, 1975.

RUIVO, M.L.P; ARROYO-KALIN, M.A.; SCHAEFER, C.E.R.; COSTI, H.T.; ARCANJO, S.H.S.; LIMA, H.L.; PULLEMAN, M.M.; CREUTZBERG, D. The use of micromorphology for the study of the formation and properties of Amazonian Dark Earths. In: LEHMANN, J.; KERN, D.C.; GLASER, B.; WOODS, W. Amazonian Dark Earths: Origin, Properties, Management. The Netherlands: Kluwer Academic Publishers, 2003.