Desenvolvimento de leguminosas herbáceas perenes, semeadas na época das águas no sul do Tocantins.

O objetivo deste trabalho foi avaliar o desenvolvimento de leguminosas herbáceas perenes semeadas na época das águas no sul do Tocantins, onde foram utilizadas: cudzu tropical (Pueraria phaseoloides), siratro (Macroptilium atropurpureum) e centrosema (Centrosema pubescens). O estudo foi conduzido na Universidade Federal do Tocantins, no município de Gurupi-TO, com delineamento experimental em blocos casualizados com quatro repetições avaliando: velocidade de emergência; capacidade de cobertura do solo; supressão sobre as plantas invasoras; decomposição e acúmulo de nutrientes na parte aérea. O siratro apresentou maior velocidade de emergência, enquanto o cudzu tropical obteve crescimento mais lento, porém reduziu maior número de plantas invasoras. Não foi observada diferença significativa entre os tratamentos na decomposição dos resíduos. A centrosema proporcionou maior aporte de N e P, e quanto aos demais macronutrientes, não foi observada diferença estatística

Estoque de Carbono e Nitrogênio e Abundância Natural de δ13C na Estação Ecológica de Pirapitinga, MG

RESUMO A avaliação integrada dos atributos físicos, estoque de carbono (EstC) e de nitrogênio (EstN) além da abundância natural de δ13C do solo se mostram eficazes na detecção de mudanças ocorridas na paisagem. Portanto, o objetivo deste estudo foi avaliar e comparar a densidade do solo, EstC, EstN e abundância natural de δ13C em perfis de solo de diferentes fitofisionomias da Estação Ecológica de Pirapitinga – EEP visando elucidar as mudanças ocorridas nesse ambiente. Para isso, foram coletadas e analisadas amostras de terra em profundidade de até um metro nas diferentes fitofisionomias da EEP. Os maiores teores de argila do solo e densidade de plantas das fitofisionomias florestais proveram maiores EstC e EstN e menores valores de densidade do solo em comparação às demais vegetações campestres. O δ13C revelou que as áreas das fitofisionomias florestais eram antes ocupadas preponderantemente por plantas do ciclo fotossintético C4, semelhantes à vegetação campestre encontrada atualmente na EEP

Hardening and Stability of Plinthic Materials of the Araguaia River Floodplain under Different Drying Treatments

ABSTRACT Plinthite and petroplinthite occur frequently in Brazilian soils, but there is little information on the behavior of these materials. The aim of the present study was to assess the effect of different drying periods on the hardening and stability of plinthic materials of soils in the floodplain of the Araguaia River and the João Leite stream in Goiás. Soil samples were collected, with the aid of 0.10 m high and 0.15 m diameter PVC cylinders, directly from the plinthic horizons of five profiles of Plintossolos Argilúvicos (Plinthosols). Plinthite and soil matrix subsamples were obtained from these samples. Homogeneous petroplinthite samples were collected from the concretionary horizon of a Plintossolo Pétrico (Plinthosol) profile, and these were separated into subsamples with the aid of a rock hammer. All subsamples were dried in two manners: air drying and drying in a forced ventilation oven for 10, 20, 40, 80, and 160 days. Compressive strength and degree of stability were assessed. The results show a considerable variety of responses to the compressive force applied to the plinthite and petroplinthite samples in the same horizon and among the different profiles examined

Reversibility of the Hardening Process of Plinthite and Petroplinthite in Soils of the Araguaia River Floodplain under Different Treatments

ABSTRACT Although ferruginous materials occur frequently in soils of tropical regions, information about the reversal of the hardening process of these materials is scarce. This study assessed the influence of different chemical treatments and periods of immersion on the reversibility of the hardening process of plinthite and petroplinthite in soils of the Araguaia River plain. Soil samples were collected from the plinthic horizons in 0.10 m high and 0.15 m diameter PVC cylinders and divided into subsamples with a rock hammer. Homogeneous petroplinthite samples were also collected and broken into subsamples with a rock hammer. The plinthite and petroplinthite subsamples were subjected to five immersion treatments: distilled water, calcium carbonate solution, sodium hydroxide solution, sodium hydroxide solution + sodium hexametaphosphate, and acidic solution. The subsamples were immersed for 20, 40, 80, and 160 days. The dispersion and stability degrees and compressive strength in these subsamples were assessed. The wet aggregate stability test indicated no impact on the structural stability of plinthite and petroplinthite subsamples subjected to the treatment with different chemical agents, demonstrating the non-reversibility of the hardening process of these materials of the Araguaia River floodplain, under the studied conditions

Paleoenvironmental Characterization of a High-Mountain Environment in the Atlantic Forest in Southeastern Brazil

ABSTRACT: Records of changes in the phytosociological structure of vegetation can be observed more clearly in soils that have more significant accumulation of organic matter, like those occurring in high-mountain environments. The aim of this study was to characterize soils formed in high-mountain environments in the Itatiaia National Park (INP), state of Rio de Janeiro, southeastern Brazil, and to discuss the potential of preserved phytoliths as markers of vegetative history and environmental factors. Four profiles were selected, which were morphologically described and evaluated for their physical and chemical properties. For phytolith analysis and high-resolution determination of the stable carbon isotopes, samples were collected at 0.10 m intervals. The profiles showed highly similar morphological characteristics, with peat deposits and colluvial sediments as source material, produced in the highest parts of the landscape. High-mountain soils in the INP have properties related to high contents of organic matter, like high acidity, low base saturation, and high CEC values due to high H+ contents. The soils are formed by the addition of plant residues, which accumulate due to the cold and humid climate during most of the year in these environments. The phytolith assemblage had a high frequency of morphotypes characteristic of temperate, cold, and high elevation intertropical regions, especially of Pooideae plants. The phytolith indexes indicated open vegetation environments with a predominance of C3 grasses, suggesting cold climate conditions, and corroborating the δ13C isotopic values. The results of phytolith analysis of the profiles reflected characteristics related to soil genesis. Organism is the main soil formation factor, conditioned by the factors relief (elevation) and climate, which resulted in low temperatures and lead organic matter accumulation

Genesis and Classification of Soils Containing Carbonates in a Toposequence of the Bambuí Group

ABSTRACT The Bambuí Group, formed from siliciclastic sediments deposited on an extensive epicontinental platform at the end of the Neoproterozoic era, is characterized by limestones with fine to very fine texture. Limestone-derived soils in the southeast of Tocantins state, Brazil, are less notorious than similar soils in other regions of Brazil and their characterization could contribute to the Brazilian System for Soil Classification (SiBCS). Given that little is known of these soils, despitetheir agricultural potential, the objective of this study was to characterize their properties and the processes leading to soil of genesis, and also contribute to developing the Brazilian System of Soil Classification (SiBCS). Soils profiles were located on the summit (P1), shoulder (P2), backslope (P3), and footslope (P4) of a toposequence in the municipality of Lavandeira, Tocantins. Morphological, physical, chemical, and mineralogical properties of the profiles were determined. The soils were classified as: P1 - Chernossolo Rêndzico Lítico típico (Lithic Haplustolls); P2 - Cambissolo Háplico Ta Eutrófico léptico hipocarbonático (Lithic Haplustolls); P3 - Cambissolo Háplico Carbonático léptico (Lithic Haplustepts); and P4 - Luvissolo Háplico Órtico típico (Typic Rhodustalfs). All the profiles showed high contents of silt, calcium, and magnesium, which resulted in high pH and low exchangeable aluminum content. Base saturation and calcium carbonate equivalent contents were also high, and the horizons showed dark colors due to high organic matter content, which contained humin as the dominant fraction. Mineralogical analysis of the clay fraction indicated predominance of hydroxy-interlayered vermiculite, followed by illite, kaolinite, and quartz, whereas the sand fraction exhibited reflections characteristic of the quartz mineral. Given P4 contents of calcium carbonate equivalent above 50 g kg-1 and the relevance of this feature for agriculture, we propose the inclusion of hypocarbonate as a criterion for classification of Luvissolos Háplicos Órticos at the subgroup level

Economic viability of Phaseolus vulgaris (BRS Estilo) production in irrigated system in a function of application of leaf boron

Foliar fertilization may be a viable strategy to boron supply in irrigated cropping systems with common beans (Phaseolus vulgaris), since it prevent B leaching. The aim of this work was to evaluate the economic viability and physiological parameters of the common beans production in irrigated cropping systems using sources and increasing foliar boron doses. A field experiment was carried out using an experimental block design in a factorial scheme 2 × 5 × 3, with two sources of B (boric acid and borax) and five doses: 0 (control), 2, 4, 6 e 8 kg ha−1, with three repetitions. Foliar B applications were performed at 40 days after seeds germination, in pre-flowering stage. Physiological process (transpiration, stomatal conductance, CO2 internal concentration, net photosynthesis, and relative chlorophyll index), B level in leaves and grain yield were measured. These data were used to determine the economic viability of B fertilization in common beans. Both boric acid and borax increased B levels in common beans leaves. Borax affected some physiological process reducing stomatal conductance and increasing net photosynthesis. Using borax, the highest net photosynthesis was observed at a rate of 4 kg ha−1, while the boric acid increased net photosynthesis linearly after increasing B doses application. An enhance of 311 kg ha−1 in the grain yield was observed using borax related to the control (without B application); however, grain yield decreased linearly after application of increasing B doses, as boric acid. Comparing the economic viability of sources and doses of B, the highest profitability is obtained using borax at a rate of 4 kg ha−1, which promoting a differential profit of US$534.44 per hectare compared to common beans cropping without B