Ademir Fontana

Efeito da cobertura viva com leguminosas herbáceas perenes na agregação de um argissolo

Tropical soils under continuous cultivation undergo fast degradation, leading to crop production decline, mainly due to erosion and reduction of soil organic matter levels. Soil protection with live mulching is one of the alternatives to alleviate these effects and to control soil degradation. This study was conducted to evaluate the root distribution and morphology of three perennial herbaceous leguminous species, as well as its effects on soil aggregation and organic carbon content when used as live mulching. The experiment was carried out on a Typic Haplustult soil in the experimental area of EMBRAPA Agrobiologia, Seropedica, State of Rio de Janeiro, Brazil, arranged in a completely randomized block design with three replicates. Treatments consisted of soil-covering with three herbaceous leguminous species (Arachis pintoi, Pueraria phaseoloides and Macroptilium atropurpureum) and a control treatment without live mulching, kept weed-free. Soil was sampled at depths of 0-5 and 5-10 cm for aggregate stability analysis and at depths of 0-5; 5-10; 10-20 and 20-40 cm for root distribution and morphology. A higher percentage of aggregates in the > 2.0 mm class was observed under A. pintoi and P. phaseoloides covers, 38 % above the control treatment mean. The values of mean weigth diameter aggregates of soil for leguminous treatments were also higher than in the weeded area for both depths, demonstrating the favorable effect of live mulch on soil aggregate stability. An increase in the organic soil carbon level was observed for the treatment with A. pintoi. Root morphology analysis showed that A. pintoi presented an intermediate root radius and higher root mass and area compared to other species, which may explain its positive effect on soil aggregation.

Distribution of Organic Carbon in the Humic Fractions of Diagnostic Horizons from Brazilian Soils

Abstract This study was developed on 52 soil profiles, 61 surface diagnostic horizons, and 26 subsurface diagnostic horizons classified according to the Soil Taxonomy and Brazilian Soil Classification System (SiBCS) as Mollisols (Chernossolos), Spodosols (Espodossolos), Entisols (Gleissolos), Oxisols (Latossolos), and Histosols (Organossolos). The objective was to quantify the carbon (C) in organic matter fractions and to correlate it with soil chemical attributes. Soil organic matter was fractionated into fulvic acids (C‐FAF), humic acids (C‐HAF), and humin (C‐HUM), and the ratios C‐HAF/C‐FAF and AE (alkaline extract)/C‐HUM were calculated. Humin was the predominant fraction in Mollisols and Oxisols, which showed values of AE/C‐HUM and C‐HAF/C‐FAF lower than 1.0. The humin fraction was also predominant in surface horizons of Spodosols and Entisols, whereas a higher content of C‐FAF and C‐FAH was observed in the subsurface horizons, with values higher than 1.5 for the AE/C‐HUM ratio. C‐HAF was predominant in the Histosols, and C‐HAF/C‐FAF ratio values were higher than 2.0. The highest correlation values with soil attributes were observed for C‐HAF, C‐HUM, and total organic C with pH, sum of bases, and cation exchange capacity. The differences in humic substances distribution was a useful parameter to characterize soil orders in the Brazilian soil classification system and to understand pedogenic processes.

Caracterização e classificação de solos em uma topossequência sobre calcário na serra da Bodoquena, MS

The soils in the Serra da Bodoquena, a mountain chain in the state of Mato Grosso do Sul, Brazil, have peculiar features that differ from other regions of the Cerrado-Pantanal biome. This study aims to characterize soils formed on limestone, based on the physical, chemical and mineralogical properties and organic matter. A toposequence on limestone was selected and profile pits were opened on the summit (P1), backslope (P2), footslope (P3) and toeslope (P4 and P5). The profiles were morphologically described and physical, chemical and mineralogical analyses were carried out in all horizons. According to the Brazilian System of Soil Classification (SiBCS), the studied soils were classified as: (P1) Organossolo Folico Saprico litico - OOs (Litic Ustifolist); (P2) Chernossolo Haplico Ortico tipico - MXo (Typic Haplustoll); (P3) Chernossolo Argiluvico Ortico tipico - MTo (Typic Haplustoll); (P4) Gleissolo Melânico Carbonatico chernossolico - GMk1 (Typic Epiaquoll); and (P5) Gleissolo Melânico Carbonatico organossolico - GMk2 (Terric Haplosaprist). The color of all studied profiles was dark in the surface horizons, and reddish or grayish in deeper layers, according to the drainage conditions. Base saturation was high in all layers, with calcium as dominant cation in the exchangeable complex. Humin was the dominant organic carbon fraction of the studied soils. A mineralogical analysis showed the presence of calcite in the sand fraction in the soil profiles GMK1 and GMk2 and kaolinite, illite and montmorillonite in the clay fraction of all soils. The occurrence of Ustifolist in non-mountainous environments, different from the characterization by the SiBCS, suggests a greater range of possible environmental conditions for the occurrence of this suborder.

Substâncias húmicas como suporte à classificação de solos brasileiros

The humic substances that compose the soil organic matter participate actively in the pedogenetic soil processes, particularly in the Histic (Histic), Mollic (Chernozemic), Umbric (Humic) and Spodic (Spodic) diagnostic horizons. This study aimed to determine organic C amounts in the soil humic substances and evaluate their applicability for diagnostic horizons recognition. Fifty-six diagnostic soil horizons from different Brazilian regions were used, 52 from surface horizons or epipedons (H histic, A mollic, A proeminent, A humic and A moderate) and four subsurface (B spodic). Soil chemical and physical properties and the organic C amounts in the fulvic acid fraction (C-FAF), humic acid fraction (C-HAF) and humin (C-HUM) were determined by well-established methods. The C-HAF/C-FAF ratio and C-AE/C-HUM ratio (C-AE = C-FAF + C-HAF) and the percentage of each fraction in the total organic C (TOC) were calculated and all data were submitted to multivariate analysis. In the organic horizon, the amounts of H histic were highest and C-HUM and C-HAF amounts similar. C-HUM was predominant in the major mineral horizons, followed by C-HAF in the A mollic and A humic horizons, and by C-FAF in the A proeminent and A moderate horizons. A greater proportion of either C-FAF or C-HAF were observed in B spodic horizons. Based on canonical analysis, we identified the variables that could be used to separate diagnostic horizon types. The horizons with low influence of organic matter were distinguished from those with greater influence by cluster analysis. With the discriminatory analysis, satisfactory results were obtained for the classification of diagnostic horizons based on humic substance variables, compared to the standard classification. Multivariate analysis indicates that the distribution of C in the humic substances can be used to separate C-rich diagnostic horizon types of tropical soils in Brazil.

Validation of the near infrared spectroscopy method for determining soil organic carbon by employing a proficiency assay for fertility laboratories

Current research indicates that near infrared (NIR) spectroscopy is the most promising alternative technique for the determination of soil organic carbon (SOC) in laboratories worldwide and that it may serve as a total or partial replacement for the traditional wet chemistry methods. In this research, NIR spectroscopy was developed and validated as a method for the determination of SOC aiming to promote the use of NIR technology in the soil laboratories of Brazil as a routine analysis method. To this end, multivariate calibration models were constructed from a large number of soil samples (1490 samples) that encompassed the variability of Brazilian soils. These models were validated by submitting the concentrations of soil organic matter (SOM) as determined by NIR spectroscopy to the proficiency assay for fertility laboratories, which is coordinated by the Brazilian Agricultural Research Corporation (Embrapa Soils). The proposed methodology using NIR spectroscopy received the excellence index of quality, which gives a certificate seal issued by the interlaboratory programme. Therefore, the robustness of the NIR method was proved in a conclusive way by a proficiency test programme dedicated to evaluating the reference method for SOM determination employed by over a hundred soil laboratories in Brazil.

Matéria orgânica de horizontes superficiais em topolitossequências em ambiente de Mar de Morros, Pinheiral, RJ

O objetivo deste trabalho foi quantificar o carbono orgânico e as fracoes humicas de horizontes superficiais de perfis de solo em tres topolitossequencias no ambiente de Mar de Morros, no municipio de Pinheiral, RJ. Foram selecionadas as topolitossequencias: T1 (basalto), T2 (muscovita-biotita-gnaisse) e T3 (gabro). Os horizontes superficiais de 14 perfis de solo, sob cobertura de pastagem (T1 e T3) e pastagem mista nao manejada e leguminosa (pasto sujo/capoeira) (T2), foram descritos e coletados para analises quimicas, fisicas e do teor de carbono nas fracoes humicas. Os teores de carbono orgânico variaram de acordo com o material de origem e decrescem na seguinte ordem: T3 > T1 > T2. Os teores de carbono orgânico aumentam do topo para a varzea na T1, ocorrendo o inverso na T3 e sem um padrao definido na T2. A fracao humina predominou em todos os perfis de solo das topolitossequencias e foi seguida pela fracao acidos fulvicos na T1 e de forma equitativa entre as fracoes acidos fulvicos e acidos humicos na T2 e T3. Considerando o ambiente similar em termos da vegetacao original e o uso agricola, as mudancas no carbono do solo e nas fracoes humicas podem refletir as interacoes com os componentes minerais e processos pedogeneticos, influenciados pelo material de origem e o relevo.

Taxonomia de solos desenvolvidos sobre depósitos sedimentares da formação Solimões no estado do Acre

Os solos do Estado do Acre na maioria sao formados sobre material de origem com grande influencia da orogenese Andina, com elevados teores de Ca2+, Mg2+ e Al3+ concomitantemente, associado as combinacoes diferenciadas dos valores da CTC, V e m. O objetivo deste trabalho foi caracterizar e classificar os solos de uma topossequencia sobre material sedimentar da Formacao Solimoes, no municipio de Feijo, Acre. Foram abertas trincheiras em tres pontos de uma topossequencia: terco superior (P1), terco medio (P2) e terco inferior (P3). Os solos foram analisados quanto a morfologia, granulometria (areia, silte e argila), complexo sortivo (Ca2+, Mg2+, Na+, K+ e Al3+), acidez potencial (H+Al), P assimilavel, pH (agua e KCl), superficie especifica, ataque sulfurico (oxidos de Fe, Al, Ti e Si), mineralogia (fracoes areia, silte e argila). Os solos foram classificados segundo o Sistema Brasileiro de Classificacao de Solos (SiBCS, 2006) e apresentada uma proposta de classificacao considerando as peculiaridades do solos da regiao. Os solos tem baixo grau de desenvolvimento pedogenetico, com minerais da fracao argila de alta atividade, alem da presenca de minerais primarios, como feldspatos e plagioclasios, nas fracoes areia e silte. Os solos foram classificados segundo o SiBCS atual como Argissolo Vermelho Alitico plintico (P1), Argissolo Acinzentado Distrofico plintico (P2) e Cambissolo Haplico Ta Eutrofico tipico (P3).

Organic phosphorus in diagnostic surface horizons of different Brazilian soil orders

Em solos tropicais, a disponibilidade de fosforo (P) pode ser regulada pela decomposicao e mineralizacao da fracao labil de P orgânico (Po), tornando necessarios estudos para saber a sua real contribuicao no solo. O objetivo deste trabalho foi avaliar o teor de Po total e labil em horizontes superficiais de diferentes classes de solo e quais as propriedades do solo exercem controle na acumulacao dessas fracoes de P. Foram estudadas amostras de diferentes horizontes diagnosticos superficiais, a saber: H e O histico; A chernozemico; e A humicos, coletados em varios estados do Brasil. Para a determinacao das fracoes totais de P inorgânico (Pi) e orgânico (Po), foi usado o metodo da extracao-sequencial acido-alcalina, e a fracao labil de P foi determinada pela extracao com bicarbonato de sodio. A taxa de recuperacao de Pi + Po em relacao a extracao nitrico-perclorica do P total (PT) variou de 46 a 99 %. O Po total variou entre 35 e 1077 mg kg-1, com uma media de 298 mg kg-1. Para a fracao labil do Po, os teores variaram entre 7,2 e 99,5 mg kg-1, com uma media de 27,1 mg kg-1. O Po variou, em media, de 36 a 46 % do P total extraido. Em relacao ao P labil, o Po representou mais de 70 % para todos os horizontes diagnosticos. O PT foi o principal atributo controlador da acumulacao de Po nos solos pelas analises de correlacao e regressao multipla. Verificou-se que horizontes com baixa capacidade de adsorcao de P proporcionaram alta labilidade de Po.

Caracterização, potencial agrícola e perspectivas de manejo de solos leves no Brasil

Light soils occupy 8% of the Brazilian territory and are especially expressive in the new and last agricultural frontier in Brazil: the Matopiba region – in the states of Maranhão, Tocantins, Piauí, and Bahia –, where they represent 20% of the area. These soils fit into the textural classes of sand and loamy sand or sandy loam, down to 0.75-m soil depth or deeper, and they are mainly represented by Neossolos Quartzarênicos (Quartzipsamments) and, partly, by Latossolos (Oxisols) and Argissolos (Ultisols). The understanding of soil functioning depends on the establishment of distinguishing criteria for: organic matter dynamics; content and mineralogy of the clay fraction; coarse sand and total sand contents, in relation to those of fine sand; mean diameter of the sand fraction; and water retention capacity. These criteria can contribute for the zoning and for the conservation and fertility management of light soils, as well as for the estimation of their agricultural potential. Integrated production systems, such as crop-livestock and crop-livestock-forestry integration, besides no-tillage with crop rotation, mixed forestry planting with legumes, and the use of green manure and cover crops are relevant for the proper management of these soils. The objective of this review was to characterize light soils and to highlight the main challenges regarding their agricultural potential and their conservation and fertility managements, in face of the expansion and consolidation of the new Brazilian agricultural frontier.

Spodosols in Brazil: distribution, characteristics and diagnostic attributes of spodic horizons

Spodosols are reported in specific environments of Brazil, such as sandy materials in the Amazon and Pantanal basin, sandbanks in the coastal fringes and coastal tableland areas, and a few in high-altitude mountains with quartz-rich rocky substrates. This study describes variations in characteristics and attributes of spodic horizons from soils classified as Spodosols in Brazilian pedoenvironments. Data were obtained from the literature, comprising landscape and location, morphological characteristics, physical and chemical attributes of Spodosol profiles, classified by the Brazilian Soil Classification System (SiBCS). The data grouped according to the pedoenvironments demonstrated the predominance of the sand fraction in the spodic horizons. The finer texture influences the organic carbon and sum of bases accumulation. Soils from the Pantanal basin with high pH values and low organic carbon content differ from the central concept of Spodosols and the podzolisation process. The aluminium and iron extractable by selective dissolution indicate higher participation of aluminium in detriment to iron. The establishment of quantitative values in the SiBCS for attributes associated with the podzolisation process is important to correlate with international soil taxonomic systems and global databases.