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Made available in DSpace on 2022-05-01T11:54:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-01-01 Soil tillage is a high-cost operation in the replanting of sugarcane fields. Thus, measures to reduce this cost are desirable, provided that they promote good physical conditions for sugarcane development. The objective of this study was to evaluate the effect of chiseling in total area and in the planting row on the physical attributes of Oxisol and Ultisol after soil tillage and after sugarcane planting. The experimental design was in large and uniform plots, with two treatments and ten replicates. The Oxisol and Ultisol had clay contents of 590 and 168 g kg−1 in the 0.00–0.40 cm layer. Treatments consisted of soil tillage with chiseling in the planting row and with chiseling in total area. After soil chiseling and after planting, undisturbed soil samples were collected in each experimental plot, in three layers (0.00–0.10; 0.10–0.20 and 0.20–0.40 m) and at two sampling sites (row and interrow). In both soils, chiseling in total area was efficient to reduce soil density and increase macroporosity in sugarcane interrows, compared to chiseling in the row. The values of the physical attributes of the soils evaluated, in rows and interrows, were similar in the areas with chiseling in total area and row chiseling after sugarcane planting. Changes in Oxisol and Ultisol structure due to chiseling did not persist after sugarcane planting. The soil under row chiseling system has physical quality similar to that of the soil under total area chiseling system, regardless of texture. School of Agricultural and Veterinarian Sciences São Paulo State University (Unesp) School of Agricultural and Veterinarian Sciences São Paulo State University (Unesp)

Wetting and drying (W-D) cycles are responsible for significant changes in soil structure. Soil often undergoes irreversible changes affecting infiltration and solute retention through W-D cycles. Thus, it becomes essential to evaluate how soils under natural conditions are altered by W-D cycles. This study analyzed two non-cultivated (from grassland and secondary forest) Oxisols (Typic Hapludox and Rhodic Hapludox) of different textures under 0 and 6 W-D cycles. The main results obtained showed that soil water retention was mainly affected in the driest regions (smaller pore sizes). The contribution of residual pores to total porosity increased with 6 W-D and transmission pores decreased in both soils. The Rhodic Hapludox presented differences in water content at field capacity (increase), while the Typic Hapludox showed alterations at the permanent wilting point (increase), affecting the amount of free water (Rhodic Hapludox) and water available to plants (Typic Hapludox). Both soils showed increases in imaged porosity with 6 W-D. Variations in the contribution of small and medium rounded pores, mainly large and irregular (with an increase in both soils not significant in the Rhodic Hapludox), could explain the results observed. The micromorphological properties were mainly influenced by changes in the number of pores, in which smaller pores joined, forming larger ones, increasing the areas occupied by larger pores. Overall, this study showed that the investigated soils presented pore systems with adequate water infiltration and retention capacities before and after continuous W-D cycles.

Iodine deficiency disorders (IDD) in sub-Saharan African countries are related to low dietary I intake and generally combatted through salt iodisation. Agronomic biofortification of food crops may be an alternative approach. This study assessed the effectiveness of I biofortification of green vegetables (Brassica napus L and Amaranthus retroflexus L.) grown in tropical soils with contrasting chemistry and fertility. Application rates of 0, 5 and 10 kg ha−1I applied to foliage or soil were assessed. Leaves were harvested fortnightly for ~ 2 months after I application before a second crop was grown to assess the availability of residual soil I. A separate experiment was used to investigate storage of I within the plants. Iodine concentration and uptake in sequential harvests showed a sharp drop within 28 days of I application in all soil types for all I application levels and methods. This rapid decline likely reflects I fixation in the soil. Iodine biofortification increased I uptake and concentration in the vegetables to a level useful for increasing dietary I intake and could be a feasible way to reduce IDD in tropical regions. However, biofortification of green vegetables which are subject to multiple harvests requires repeated I applications.

Crop rotation associated with the use of cover crops promotes the introduction of crop residues to the soil, with direct and indirect effects on theavailability of plant nutrients, especially nitrogen (N). The objectivesof this study wereto estimate the N utilization from15N-ureaand cover crop residues (labelled with 15N)of maizecropsgrown in succession,andevaluate the effectsof the isolated and combined use of cover crops and urea on maize plant height, yield components,andgrain yield, grownunderano-tillage system. Field researchwas conductedin anOxisol (Rhodic Haplustox), Cerrado (Savannah) phase. The experimental design was a randomized block with 20 treatments and four replications in a 5x4 factorial scheme. The treatments were four cover cropsspecies: sunnhemp (Crotalaria juncea L.), pigeon pea (Cajanus cajan(L.) Millsp), green velvetbean (Mucuna prurens),and millet (Pennisetum glaucumL.) + spontaneous vegetation (fallow in the off-season),combined with four N rates: 0, 30, 90,and 150 kg ha-1, applied at the sowing and topdressingstages. The results showed that legume covercropsprovided maize grain yieldsequivalent tothe applicationof 80-108 kg ha-1N as urea. TheureaN utilizationby the maize was at an averageof43.5% of the appliedamount.The results indicatethat cover crops, particularly legume cover crops,are an important source of N to non-legume cereals.Legumes used as cover crops can replace nitrogen fertilizers of more than 80 kg ha, which is both environmentally and economically viable for corn production. Made available in DSpace on 2020-11-07T09:13:52Z (GMT). No. of bitstreams: 1 AJCS-Article-2020-1.pdf: 1000820 bytes, checksum: 6a8dc85d340a4761772e6853c369f511 (MD5) Previous issue date: 2020

The conversion from native forest to other land-use systems can decline the soil organic carbon (SOC) in tropical soils. However, conservationist management could mitigate SOC losses, promoting the functioning and stability of agricultural soils. This study aimed to address the influence of conversion from native forest to different land-use systems on SOC fractions in Northeastern Brazil. Topsoil soil samples were collected in areas under pasture (PAS), no-tillage (NT1 and NT2), eucalyptus (EUC), and native forests of Cerrado in Northeastern, Brazil. Total organic C, microbial biomass (MBC), particulate (POC), and mineral-occluded organic C (MOC), as well as fulvic acids (C-FA), humic acids (C-HA), and humin (C-HUM) fractions were accessed. The results showed that land conversion maintained similar levels of humic fractions and total organic carbon (TOC) stocks in the PAS, NT1, NT2, and EUC as compared to native Cerrado. Soils with the input of permanent and diverse fresh organic material, such as NT2, PAS, and EUC, presented high levels of MBC and POC, and the lowest C-FA:TOC and C-HA:TOC ratios. The land conversion to agricultural systems that include cropping rotations associated with pasture species such as Mombasa grass and eucalyptus prevents topsoil losses of active C compartments in the Cerrado of the Brazilian Northeast. It suggests that sustainable and conservationist management should be emphasized to maintain and improve the status of soil organic C.

The objective of this work was to determine pedotransfer functions to predict water retention at the -33 and -1500 kPa matric potentials of soils under Cerrado, in the south of the state of Mato Grosso, Brazil. Samples (n=156) were collected for model calibration (n=124) and validation (n=32). A stepwise multiple regression was used to determine pedotransfer functions. Willmott’s index of agreement, root-mean-square error, Pearson’s correlation coefficient, and the confidence index were used to evaluate the performance of the functions and to compare them with those described in the literature. The most efficient variables to estimate water retention were: microporosity, total sand, and clay at -33 kPa; and total sand, silt and clay at -1500 kPa. The regional pedotransfer functions explained more than 94% of water retention variance in the studied soils. The reliability of the functions to predict water retention increased, at -33 kPa, with the use of the structural property microporosity and, at -1500 kPa, with the use of granulometric parameters. The studied regional pedotransfer functions predict water retention at the -33 and -1500 kPa matric potentials of soils under Cerrado, in southern Mato Grosso, better than the functions described in the literature.

A growing demand for resources has led to the expansion of agricultural areas worldwide. However, land conversion associated with poor soil management might lead to soil physical degradation. We investigated the effects of land conversion on soil physical properties in the Brazilian Cerrado region, under native Cerrado vegetation (NV)—pasture (PA) and NV—cropland (CL) conversion scenarios. Soil physical properties related to compaction, pore size distribution, and structure stability were assessed up to a 30 cm depth. Additionally, carbon levels of soil organic matter fractions (particulate and mineral-associated organic matter) were determined. Our results indicate that the compaction process equivalently reduced the soil porosity in PA and CL. However, soil penetration resistance was higher in PA (~2.5 MPa) than in CL (~1.5 MPa), as well as the stable mean weight diameter of soil aggregates. The highest total and labile organic carbon levels were observed in CL, while the lowest levels of total and labile organic carbon occurred in PA (smaller than in CL). These results suggest that the higher structural stability found in PA was mediated by the predominance of stabilized carbon (a decrease in the proportion of soil labile carbon), causing the gaining of soil strength under negligible soil volume variation (in comparison with CL). Our results suggest that the reduction in the soil porosity by compaction due to PA and CL uses can equivalently reduce macropore space and soil hydraulic functioning, and that soil carbon quality alterations (i.e., labile vs. stabilized fractions) are responsible for the gain in soil strength in long-term degraded PA areas. Future research should focus on understanding the magnitude in which soil organic matter controls soil physical attributes, such as soil strength in these expansion areas, and whether this gain in soil strength limits plant development and compromises productivity in the long term.

[Abstract] The disposal of treated effluents on soil is the main final use of wastewater in Brazil. Although this practice can promote improvements of some soil attributes, there is a need for monitoring in order to ensure that potential environmental impacts are not harmful. Thus, the purpose of this study was to evaluate the effects of treated effluent from a poultry slaughterhouse on the chemical attributes of an Oxisols, in Matelândia-PR, Brazil under drip irrigation. The soil attributes P, K, Fe, Cu, Zn, Mn, pH in CaCl2, H + Al, Al, Ca, Mg, cation exchange capacity (CEC), and percent base saturation (V) were evaluated under four effluent application rates, 0, 100, 200 and 300 m³ ha-1 d-1 with treated effluents on three successive sampling dates. As main results it was observed that high irrigation rates increased soil phosphorus and potassium concentrations. In addition, an association between the increase of soil potential acidity and exchangeable acidity was detected, although pH did not vary significantly either between treatments or between sampling dates. [Resumo] A disposição de efluentes tratados sobre o solo pode ser considerada o principal destino final de águas residuárias no Brasil. Embora possa promover melhorias em relação a alguns atributos do solo, esta prática precisa ser monitorada para garantir que os impactos ambientais não sejam negativos. Assim, objetivou-se com este trabalho avaliar os efeitos da disposição, por gotejamento, do efluente tratado de um abatedouro de aves sobre os atributos químicos de um Latossolo, em Matelândia, PR. Os atributos do solo: P, K, Fe, Cu, Zn, Mn, pH em CaCl2, H + Al, Al, Ca, Mg, capacidade de troca catiônica (CTC), saturação por bases foram avaliados sob quatro taxas de irrigação, 0, 100, 200 e 300 m³ ha-1 d-1, com efluentes tratados em três datas sucessivas de amostragem. Como principais resultados observou-se que as altas taxas de aplicação do efluente praticadas, influenciaram no incremento das concentrações de fósforo e potássio no solo. Além disso, pôde-se observar uma relação entre o aumento da acidez potencial e acidez trocável, mesmo que o pH não tenha variado tanto nem entre os tratamentos nem entre as ocasiões de coletas de dados.

Deforestation of native tropical forests has occurred extensively over several decades. The plantation of fast-growing trees, such as Acacia spp., is expanding rapidly in tropical regions, which can contribute to conserve the remaining native tropical forests. To better understand belowground biogeochemical cycles and the sustainable productivity of acacia plantations, we assessed the effects of vegetation (acacia plantations vs. native forests) and soil types (Oxisols vs. Ultisols) on soil properties, including the diversity and community structures of bacteria- and fungi-colonizing surface and subsurface roots and soil in the Central Highlands of Vietnam. The results in surface soil showed that pH was significantly higher in acacia than in native for Oxisols but not for Ultisols, while exchangeable Al was significantly lower in acacia than in native for Ultisols but not for Oxisols. Bacterial alpha diversity (especially within phylum Chloroflexi) was higher in acacia than in native only for Oxisols but not for Ultisols, which was the same statistical result as soil pH but not exchangeable Al. These results suggest that soil pH, but not exchangeable Al, can be the critical factor to determine bacterial diversity. Acacia tree roots supported greater proportions of copiotrophic bacteria, which may support lower contents of soil inorganic N, compared with native tree roots for both Oxisols and Ultisols. Acacia tree roots also supported greater proportions of plant pathogenic Mycoleptodiscus sp. but appeared to reduce the abundances and diversity of beneficial ECM fungi compared with native tree roots regardless of soil types. Such changes in fungal community structures may threaten the sustainable productivity of acacia plantations in the future.

Orientadores: Mara de Andrade Marinho, Edson Eiji Matsura Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agrícola Resumo: A estrutura é um dos atributos mais importantes do solo sob o ponto de vista agrícola, sendo não somente influenciada pelo clima, atividade biológica e práticas de manejo, mas também por forças de natureza mecânica e físico-química. Nesse contexto, o trabalho teve por objetivo geral avaliar a influência do uso e do manejo agrícola sobre a qualidade estrutural de um LATOSSOLO VERMELHO Distroférrico típico (Rhodic Hapludox). A avaliação foi realizada com base em indicadores físicos tradicionais e empregando técnicas de análise micromorfológica e micromorfométrica. A pesquisa foi desenvolvida em Campinas, SP, em duas parcelas experimentais cultivadas com milho, uma sob Sistema Plantio Direto (SPD) e outra sob Sistema Convencional (SC)... Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digital Abstract: Soil structure is one of its most important attribute concerning the agricultural point of view, being influenced not only by climate, biological activity and management practices, but also by mechanical and physical- chemical forces acting in it. In this context, the main purpose of this work was to evaluate the influence of agricultural use and management on the structural quality of a Rhodic Hapludox. The evaluation was carried out considering traditional physical indicators and also by employing micromorphological and micromorphometrical techniques. The study was developed at Campinas, SP, in an experimental area with maize under no-till system (NT) and conventional system (CS)¿ Note: The complete abstract is available with the full electronic digital thesis or dissertations Doutorado Água e Solo Doutor em Engenharia Agrícola

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior Agriculture and pasture dominate the landscapes that were originally covered by Cerrado vegetation in the Triangulo Mineiro (MG). The use of conversion causes a range of environmental changes, for instance, the imbalances of the carbon stocks, the nature of carbon sources and the reduction of carbon attached to a biomass accompanied by the modifications of the properties and the soil characteristics such as density, porosity and others. Being an essential pool to carbon storage, the soils can be a source or a sink of atmospheric CO2 that depending on the cultivation and the management system adopted. The micro-region of the Triangulo Mineiro (MG) in Uberlandia has extensive areas filled by pasture. However, the geological conditions of soil and the climate are important factors that may accelerate the soil degradation when pastures is not handled properly. The objectives of this research were to evaluate the alterations in soil organic matter (SOM), the variation in the stock of soil organic carbon (Mg/ha de C), the content and nature of carbon (%C e δ13C), the carbon replacement rate derived from the native vegetation C3 (in their stable and biodegradable pools) and the C4 crop in the ground and also to determine the turnover of SOM and the technical management efficiency to store carbon in areas covered with native Cerrado (CN - vegetation type Cerradão) and the cultivated pasture with 30 years of implementation (P30). It was studied a mixed and representative complex system in the region - an area that was initially converted to agricultural use and the last 15 years has been occupied with cultivated pasture (Agric+P15). It has been also done a meta-analysis from scientific literature data in order to evaluate the soil carbon storage alterations after changing of use including different areas in the Cerrado Mineiro. The results have shown that the conversion to cultivated systems had a decrease of total porosity (Pt) and an increase of soil density (Ds) when are compared with values determined for Cerradão soils. In soil under Agric+P15 there was an impoverishment of carbon content, especially, when compared to the surface area of native vegetation. Therefore, the soil covered with P30 showed values closer to those found in native vegetation in both surface and subsurface that was an evidence of a stability of the carbon content over time. There was a decrease of the storage of SOM on the superficial layers (0-15 cm) of the cultivated soil, however, in the depth (30-60 cm), the stock given in P30 is equivalent at the storage of the soil beneath Cerrado. In agric+P15 were determined lower inventories stock at all depths. The pasture management techniques was efficient in storing carbon, mainly if was taken the sandy soil formation (between 70 and 80% of sand). The results have shown that in Agric+P15 and in P30 there were an incorporation of C originated from vegetation C4. The average replacement of SOM derived from C4 plants (in 0-15 cm) was high, with 91,3% in Agric+P15 and 99,6% in P30. Finally, the carbon derivate of native vegetation had a low stable fraction (~2,2 t/ha de C) when is compared to the biodegradable fraction. Agricultura e pastagem dominam as paisagens que originalmente eram recobertas pela vegetação de Cerrado no Triângulo Mineiro (MG). A conversão de uso causa uma série de mudanças ambientais, entre elas os desequilíbrios nos estoques de carbono, na natureza das fontes de carbono e na redução do carbono ligado à biomassa acompanhados de modificações das propriedades e características como densidade, porosidade, entre outras. Por ser um compartimento importante para o estoque de carbono, os solos podem ser uma fonte ou um sumidouro de CO2 atmosférico, dependendo do sistema de cultivo e manejo adotados. A microrregião de Uberlândia no Triângulo Mineiro (MG) apresenta extensas áreas ocupadas com pastagem. No entanto, as condições geológicas do solo e climáticas se constituem em fatores determinantes que podem acelerar a degradação dos solos quando a pastagem não é manejada adequadamente. Os objetivos desta pesquisa foram avaliar as alterações na matéria orgânica do solo (MOS), as mudanças do estoque de carbono orgânico do solo (Mg/ha de C), o teor e a natureza do carbono (%C e δ13C), a taxa de substituição do carbono derivado da vegetação nativa C3 (em seus compartimentos estáveis e biodegradáveis) e do cultivo C4 no solo e determinar o turnover da MOS e a eficiência da técnica de manejo para estocar o carbono em áreas recobertas com Cerrado nativo (CN - fitofisionomia Cerradão) e pastagem cultivada com 30 anos de implantação (P30). Estudou-se também um sistema misto e complexo representativo na região uma área convertida inicialmente ao uso agrícola e os últimos 15 anos ocupada com pastagem cultivada (Agric+P15). Realizou-se ainda uma metaanálise, a partir de dados da literatura científica, com o intuito de avaliar variações do estoque de carbono do solo após mudança de uso incluindo diferentes áreas no Cerrado Mineiro. Os resultados mostraram que a conversão para sistemas cultivados resultou na diminuição da porosidade total (Pt) e no aumento da densidade do solo (Ds) quando comparados com os valores determinados para solos do Cerradão. No solo sob Agric+P15 houve um empobrecimento de teor de carbono (%C) especialmente em superfície se comparado à área sob vegetação nativa. No entanto, o solo recoberto com P30 apresentou valores mais próximos daqueles encontrados sob vegetação nativa, tanto em superfície quanto em subsuperfície, evidenciando a estabilidade do teor de carbono ao longo do tempo. Houve decréscimo do estoque da MOS nas camadas superficiais (0-15cm) dos solos cultivados, porém, na profundidade (30-60 cm), o estoque determinado em P30 se iguala ao estoque do solo sob Cerrado. Em Agric+P15 foram determinados os menores estoques em todas as profundidades. A técnica de manejo da pastagem mostrou-se eficiente em estocar carbono, principalmente se considerar a constituição arenosa do solo (entre 70 e 83% de areia). Os resultados mostraram que em Agric+P15 e em P30 houve incorporação do C derivado de vegetação C4. A média de substituição da MOS derivada de plantas C4 (em 0-15 cm) foi alta, sendo de 91,3% em Agric+P15 e de 99,6% em P30. Finalmente, o carbono derivado da vegetação nativa possui uma fração estável baixa (~2,2 t/ha de C) quando comparada com a fração biodegradável. Doutor em Geografia

Orientador: Wanilson Luiz Silva Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociências Resumo: O uso integrado de dados geoquímicos e geofísicos em Latossolos Vermelho são pouco aplicados no Brasil, mas estes podem trazer grandes avanços nas descrições pedológicas, tanto para caracterizar verticalmente o perfil de solo quanto para determinar sua extensão lateral, de forma rápida e econômica. Neste contexto, este trabalho buscou comparar dados geoquímicos multielementares, incluindo Hg e os ETRs (elementos terras-raras), com dados geofísicos coletados com GPR (ground-penetrating radar) e SEV (sondagem elétrica vertical), para descrever três perfis de Latossolo Vermelho originados do diabásio da Formação Serra Geral, sobre extremo intemperismo, no município de Campinas-SP (ambiente tropical). Os perfis são profundos (entre 6 e 9 metros) e de textura argilosa/muito argilosa. São compostos predominantemente por caulinita, gibbsita, hematita e goethita, mas também apresentam grãos milimétricos de quartzo e magnetita (com microestrutura de exsolução de ilmenita). O GPR mostrou refletores na faixa de 3-5 metros de profundidade associados ao alto teor de argila (> 50 %). Com a SEV foi possível determinar a profundidade ao topo do perfil de solo ¿ 8 metros ¿ e diferenciar três camadas de solo, além da rocha fresca. As resistividades aparentes indicaram uma possível transição de um solo nítico para um solo latossólico. Elevados valores dos índices de intemperismo (CIA, IOL e WPI) confirmaram o grau extremo de intemperismo deste ambiente, com estágios avançados de ferralitização, especialmente nos horizontes transicionais (BC). A mobilidade dos elementos maiores e menores (TiO2 conservativo) mostraram intensa lixiviação dos metais alcalinos e alcalinos terrosos e enriquecimento residual de Al, Fe e Mn, especialmente nas bases dos perfis. A análise estatística evidenciou as diferenças entre os perfis e mostrou que a mobilidade dos metais traço está condicionada, predominantemente, a presença dos argilominerais e óxidos/hidróxidos de Fe e Al... O resumo poderá ser visualizado no texto completo da tese digital Abstract: The integrated use of geochemical and geophysical methods in Oxisols are little applied in Brazil, but these can bring great advances in pedological descriptions, both to characterize vertically the soil profile and to determine its lateral extension, quickly and cost-effectively. In this context, this study aimed to compare multielemental geochemical data, including Hg and ETRs (rare-earth elements), with geophysical data collected with GPR (ground-penetrating radar) and SEV (vertical electrical sounding), to describe the pedogeochemical evolution of three profiles of Oxisols originated from the diabase of the Serra Geral Formation, on extreme weathering, in Campinas-SP (tropical environment). The profiles are deep (6 ¿ 9 m) and clayey/very clayey texture. They consist predominantly of kaolinite, gibbsite, hematite and goethite, but also present millimeter grains of quartz and magnetite (with ilmenite exsolution microstructure). The GPR showed reflectors in the range of 3-5 meters of depth associated with high clay content (> 50 %). With SEV it was possible to determine the depth to the top of the soil profile ¿ 8 m ¿ and differentiate three layers of soils, besides the diabase. Apparent resistivities indicated a possible transition from a nitic layer to an oxisolic layer. High values of the weathering index (CIA, IOL and WPI) confirmed the extreme degree of weathering of this environment, with advanced stages of ferralisation, especially in the BC horizons. The mobility of major and minor elements (conservative TiO2) showed intense leaching of alkali and alkaline earth metals and residual enrichment of Al, Fe and Mn in the bases of the profiles. The statistical analysis evidenced the differences between the profiles and showed that the mobility of the trace metals along is conditioned, predominantly, the presence of clay minerals, oxides and hydroxides of Fe and Al... The abstract is available with the full electronic document Mestrado Geologia e Recursos Naturais Mestre em Geociências CAPES

Soil Organic Matter (SOM) plays an important in many ecosystems on the planet. Therefore, we employed elemental analysis (CHN), fluorescence spectroscopy (EEM-CP/PARAFAC), and electron paramagnetic resonance (EPR) to characterize the humic acids (HA) extracted from soils under integrated agricultural production systems (e.g. agroforestry systems (AFS)). These systems (S) included Crop (C), Livestock (L), Forest (F), and different combinations of them (CLFS, LFS, and CLS), which were compared with pastures (intensive (INT) and extensive (EXT)) and native forest (NF). For this purpose, we collected samples of a dystrophic Red-Yellow Latosol from experimental field areas which it is located at the Embrapa Pecuária Sudeste in São Carlos, São Paulo state, Brazil. Results showed that the HA humification index increased with soil depth, which is identified by complex structures more affluent in semiquinone-type free radical (SFR) and higher fluorescence intensity, especially in the AFS. Therefore, the HA from the CLFS systems had a higher aromaticity profile than HA from pastures and native forest areas, suggesting a longer lifetime to Carbon compounds. These significant findings are important for developing climate change mitigation strategies. Made available in DSpace on 2022-03-10T16:00:25Z (GMT). No. of bitstreams: 1 SpectroscopicCharacteristicsHumic.pdf: 7384588 bytes, checksum: edc95420eb6ea0fede2e19ba102b2b54 (MD5) Previous issue date: 2022

Although agriculture and livestock systems represent important sources of N2O from the soil, they may also aid in emissions mitigation, mainly when integrated systems are taken into account, such as crop-livestock-forest, for food production. This work assessed the soil N2O emissions from a tropical Oxisol under row-crop, livestock, forest monocultures, and an integrated crop-livestock-forest system in the Southern Amazon - Brazil. Soil N2O emissions were measured using static chambers from November 2014 to October 2016 in four soil use systems [row-crop, livestock, forest, and integrated crop-livestock-forest (CLF)], and in a reference area under native forest fragment. For the whole period, the average of soil N2O fluxes was 16.9, 12.2, and 15.4 µg N2O-N m-2 h-1, to row-crop, livestock, and CLF systems, respectively, all with a similar average among them. The lowest fluxes were observed in the forest system and native forest fragment, with average fluxes of 4.0 and 6.3 µg N2O-N m-2 h-1, respectively, both lower than the agricultural systems. The largest soil N2O fluxes were observed throughout the rainy seasons in the row-crop, livestock, and CLF, mostly after N-fertilizer application to the soil surface or in the planted row. As a consequence, the cumulative emissions were greater in row-crop, livestock, and CLF systems, which in the averages of two cycles emitted respectively 1.40, 1.15, and 1.27 kg N2O-N ha-1 yr-1, all different of the forest system and native forest fragment (0.33 and 0.52 kg N2O-N ha-1 yr-1, respectively). Nitrogen fertilization and soil moisture influenced soil N2O emissions of all systems assessed in the Southern Amazon. The N2O emissions took place after both factors were met, corroborating the hole-in-the-pipe model. Even with more soil use intensification, once in the same area there were three cultures in succession during a year and perennial trees, CLF did not lead to greater N2O emissions from the soil than row-crop and livestock. Thus, CLF represents a good option for N2O mitigation for the edaphic and climatic conditions of the Southern Amazon.

Intrinsic equilibrium constants of 17 representative Brazilian Oxisols were estimated from potentiometric titration measuring the adsorption of H+ and OH− on amphoteric surfaces in suspensions of varying ionic strength. Equilibrium constants were fitted to two surface complexation models: diffuse layer and constant capacitance. The former was fitted by calculating total site concentration from curve fitting estimates and pH-extrapolation of the intrinsic equilibrium constants to the PZNPC (hand calculation), considering one and two reactive sites, and by the FITEQL software. The latter was fitted only by FITEQL, with one reactive site. Soil chemical and physical properties were correlated to the intrinsic equilibrium constants. Both surface complexation models satisfactorily fit our experimental data, but for results at low ionic strength, optimization did not converge in FITEQL. Data were incorporated in Visual MINTEQ and they provide a modeling system that can predict protonation-dissociation reactions in the soil surface under changing environmental conditions. RESUMO Constantes de equilíbrio intrínseco de 17 Latossolos brasileiros representativos foram estimadas a partir de titulações potenciométricas, medindo-se a adsorção de H+ e OH- nas superfícies anfotéricas de suspensões com força iônica variada. As constantes de equilíbrio foram ajustadas a dois modelos de complexação: camada difusa e capacitância constante. O primeiro modelo foi ajustado pelo cálculo da concentração total de sítios a partir de estimativas de ajustes e extrapolação do valor de pH das constantes de equilíbrio intrínsecas ao PCLPZ (cálculo manual), considerando um ou dois sítios reativos, e também pelo programa FITEQL. O segundo modelo foi ajustado somente pelo FITEQL com um sítio reativo. Os atributos químicos e físicos do solo foram correlacionados às constantes de equilíbrio intrínsecas. Os dois modelos de complexação de superfícies se ajustaram satisfatoriamente aos dados experimentais, mas para resultados em baixa força iônica a otimização não convergiu no FITEQL. Os dados foram incorporados no Visual MINTEQ e fornecem um sistema de modelagem que pode predizer reações de protonação-dissociação na superfície do solo sob diversas condições ambientais.

Revegetation has been reported to be one of the most effective measures for reducing soil erosion on the Loess Plateau in China. The Yunwu observatory, located in the northwestern Loess Plateau of China, was selected to study the effect of vegetation succession on total carbon (C), aggregate C, and intra-aggregate particulate organic matter-carbon (iPOM-C) concentrations. The vegetation types studied, listed from the shortest to the longest enclosure duration order, were abandoned grazed grassland (Ab.G3), Hierochloe odorata Beauv. (Hi.07), Thymus mongolicus Ronnm (Th.M15), Artemisia sacrorum Ledeb (At.S25), Stipa bungeana Trin Ledeb (St.B36), and Stipa grandis P. Smim (St.G56) communities. Five sizes of aggregates were separated using the modified Yoder method (

Phosphorous (P) contents in many soils are varies highly along with their ability to provide available P to plant growth. Soils may contain very high in total P, but low in available P due to high P adsorbed by soil matrix and all their adsorbing agents. This research which using natural materials was aimed to increase P availability in some high-P absorption soils. The natural materials utilized for extracting P were organic matter, P extracting bacterial, and rock phosphate. Those materials were interacted to high P absorption soils which were: Oxisol, Inceptisol, and Andisol. The detail objectives of this research were: (1) to study the potential of P-extracting agents (organic matter, and P-extracting bacteria) in releasing P of three high P- absorption soils; (2) to quantify the -age of P coming from the treatments; (3) to calculate the efficiency of P utilization by plant; and (4) to quantify Residual P in soils. The P mobility was analyzed by radioisotope technique using KH232PO4 carrier free solution. The results showed that adding soil organic matter increased the available P by 15.24% in Oxisol, 40.18 in Inceptisol, and by 7.34% in Andisol. Plant sorption toward P from % P used efficiency(%-PUE) up to 60 days was still very low, 0.65 to 9.34%. This was in accordance with the residual P in soils which were still quite high ranging from 94% to 96% in Andisol, 91%97% in Inceptisol, and 96%-98% in Oxisol. The implication of the results of this research, however, is that the application of natural materials in improving soil P availability provides a longtimeresidual effect which could give benefit to the following crops.Keywords: Andisols; Inceptisol; Oxisols; P. diminuta; PUE; rock phosphate[How to Cite: Mudjiharjati A, TC Setiawati and MH Pandutama. 2012. Improving Phosphate Efficiency by Phosphate Solubilizing Bacteria and Organic Matter Estimated by Radio Isotop (32P) Technique in Some Soils. J Trop Soils, 17 (3) : 245-252. doi: 10.5400/jts.2012.17.3.245][Permalink/DOI: www.dx.doi.org/10.5400/jts.2012.17.3.245]

Although manioc is well adapted to nutrient-poor Oxisols of Amazonia, ethnobotanical observations show that bitter manioc is also frequently cultivated in the highly fertile soils of the floodplains and Amazonian dark earths (ADE) along the middle Madeira River. Because different sets of varieties are grown in each soil type, and there are agronomic similarities between ADE and floodplain varieties, it was hypothesized that varieties grown in ADE and floodplain were more closely related to each other than either is to varieties grown in Oxisols. We tested this hypothesis evaluating the intra-varietal genetic diversity and the genetic relationships among manioc varieties commonly cultivated in Oxisols, ADE and floodplain soils. Genetic results did not agree with ethnobotanical expectation, since the relationships between varieties were variable and most individuals of varieties with the same vernacular name, but grown in ADE and floodplain, were distinct. Although the same vernacular name could not always be associated with genetic similarities, there is still a great amount of variation among the varieties. Many ecological and genetic processes may explain the high genetic diversity and differentiation found for bitter manioc varieties, but all contribute to the maintenance and amplification of genetic diversity within the manioc in Central Amazonia. © 2017, Sociedade Brasileira de Genética.

Background and aims: The reactivity and bioavailability of soluble metal added to soil decreases with time. This process, called ageing, has mainly been investigated in temperate soils. This paper uses isotopic exchangeability to investigate Zn ageing in a range of highly weathered and/or oxide-rich soils. Methods: Changes in lability of soluble added Zn (450 mg Zn/kg soil) over time was measured in six contrasting soils, with pH adjusted to give ten treatments per soil type ranging from pH 4 to 7. Results: Decreasing extractability and isotopic exchangeability (lability) over time revealed substantial fixation of added zinc in six highly weathered/variable charge soils. Strong negative relationships between pH and solubility, and pH and lability were observed. In soils with pH > 6.5 a significant proportion of the added metal becomes non-isotopically exchangeable within 15 s of addition. Correlations between Mn solubility and Zn lability throughout the incubation demonstrated the role of redox conditions (and pH) in regulating Zn lability. Conclusions: Results showed zinc fixation was strongly related to pH and ageing time, and relatively unaffected by soil type and mineralogy. Very rapid reductions in radiolability immediately (

Soybean (Glycine max L. Merrill) crop started to be planted in the Brazilian Cerrado in the 1970's, and this region currently contributes with 57% of total soybean production in Brazil. Under natural conditions in this region, the soils present chemical limitations such as low pH, low Cation Exchange Capacity, low nutrient availability, and moreover, clayey soils have a high P fixation capacity mainly due to high contents of Fe/Al oxides. Since P is the most limiting nutrient is this region, a study was performed in the state of Maranhão, Brazil, in a Typic Hapludox, with clayey texture and low available P (extracted by resin). Treatments were defined to evaluate soybean response to broadcast Arad phosphate rock (PR) plus banded triple superphosphate (TSP) and to evaluate the soybean response to three proportions of PR and TSP. The experiment was established in October 2004 and was carried out for three consecutive crop years (2004/05 to 2006/07). The associated use of PR and TSP, in several situations, resulted in yields at least similar to that obtained with the use of the water soluble P source and, in some cases, even using lower P rates. Regarding the "mixtures", a linear response was observed when they were banded; however, when they were broadcasted, no increase in yield was observed above 50% of relative solubility. In conclusion, the association of sources differing in solubility may be a feasible agronomic option for P fertilizer management of soybeans. O cultivo de soja (Glycine max L. Merrill) na região do Cerrado iniciou-se na década de 1970 e, atualmente, representa aproximadamente 57% da produção total do Brasil. Sob condições naturais, os solos dessa região apresentam limitações químicas, como baixos valores de pH, de Capacidade de Troca de Cátions, de disponibilidade de nutrientes, bem como elevada capacidade de fixação de P nos solos de textura argilosa, principalmente pelos altos teores de óxidos de Fe/Al. Levando-se em conta que o P é o nutriente mais limitante à produção nessa região, foi instalado um experimento no estado do Maranhão, em Latossolo Vermelho-Amarelo distrófico argiloso e com baixo teor disponível de P (extraído com resina). Objetivou-se verificar a resposta da cultura à aplicação do fosfato de rocha Arad (FR) em área total mais superfosfato triplo (SFT) em aplicação localizada; e verificar a resposta da cultura a três proporções de FR e SFT. O experimento foi instalado em outubro de 2004 e conduzido por três safras consecutivas (2004/05 a 2006/07). A utilização associada de FR e SFT, em várias condições, resultou em produtividades no mínimo semelhantes à obtida com a fonte solúvel e, em alguns casos, até utilizando menores quantidades de P. Quanto às "misturas", verificou-se resposta linear para a aplicação localizada; entretanto, para a aplicação a lanço, não houve aumento na produtividade a partir de 50% de solubilidade relativa. Logo, a associação de fontes com solubilidades distintas pode ser uma opção agronomicamente viável para o manejo da adubação fosfatada da soja.

Modern soil science, spearheaded by research in Brazil has facilitated the utilization of vast areas of previously uncultivated soil long considered unsuitable for human food production into highly productive agricultural land. Naturally acid soils with high contents of aluminum and iron oxides and low CEC values and organic matter contents long considered insurmountable obstacles to crop production in tropical latitudes could be extremely productive. With continued development of the infrastructure needed by commercial agriculture Brazil has the potential to lead the world in its quest to provide food for growing human populations. A moderna ciência de solo, liderada pelas suas pesquisas no Brasil, tem possibilitado a utilização de vastas áreas de solos, durante muito tempo não cultivados por serem avaliados como inaptos para uma intensiva produção de alimentos. Hoje, ao contrário, constata-se que essas terras são altamente produtivas para a agricultura. Estas pesquisas vêm mostrando que alguns atributos naturais destes solos, como acidez, baixos teores de matéria orgânica, baixa capacidade de troca de cátions, além de altos teores de óxidos de ferro e/ou de alumínio - considerados como obstáculos à produção de boas colheitas em latitudes tropicais - podem ser superados. Com a continuação do desenvolvimento das infra-estruturas necessárias para alavancar ainda mais a agricultura comercial, o Brasil tem potencial para, em breve, liderar o mundo no que tange ao fornecimento de alimentos para as crescentes populações humanas.

No-till (NT) adoption is an essential tool for development of sustainable agricultural systems, and how NT affects the soil organic C (SOC) dynamics is a key component of these systems. The effect of a plow tillage (PT) and NT age chronosequence on SOC concentration and interactions with soil fertility were assessed in a variable charge Oxisol, located in the South Center quadrant of Parana State, Brazil (50°23’W and 24°36'S). The chronosequence consisted of the following six sites: (i) native field (NF); (ii) PT of the native field (PNF-1) involving conversion of natural vegetation to cropland; (iii) NT for 10 years (NT-10); (iv) NT for 20 years (NT-20); (v) NT for 22 years (NT-22); and (vi) conventional tillage for 22 years (CT-22) involving PT with one disking after summer harvest and one after winter harvest to 20 cm depth plus two harrow disking. Soil samples were collected from five depths (0–2.5; 2.5–5; 5–10; 10–20; and 20–40 cm) and SOC, pH (in H 2 O and KCl), ΔpH, potential acidity, exchangeable bases, and cation exchangeable capacity (CEC) were measured. An increase in SOC concentration positively affected the pH, the negative charge and the CEC and negatively impacted potential acidity. Regression analyses indicated a close relationship between the SOC concentration and other parameters measured in this study. The regression fitted between SOC concentration and CEC showed a close relationship. There was an increase in negative charge and CEC with increase in SOC concentration: CEC increased by 0.37 cmol c kg −1 for every g of C kg −1 soil. The ratio of ECEC:SOC was 0.23 cmol c kg −1 for NF and increased to 0.49 cmol c kg −1 for NT-22. The rates of P and K for 0–10 cm depth increased by 9.66 kg ha −1 yr −1 and 17.93 kg ha −1 yr −1 , respectively, with NF as a base line. The data presented support the conclusion that long-term NT is a useful strategy for improving fertility of soils with variable charge.

Long-term no-tillage (NT) leads to profile stratification of soil organic matter (SOM) pools, and the soil organic carbon (SOC) stratification ratio (SR) is an indicator of soil quality. The objective of this report is to assess the feasibility of using SOC-SR as an index for estimating SOC sequestration in NT soils. The effect of a plow tillage (PT) and NT chronosequence on the SR of SOM pools was assessed in an Oxisol in Southern Brazil (50°23′W and 24°36′S). The chronosequence consisted of six sites: (i) native field (NF); (ii) PT of the native field (PNF-1) involving conversion of natural vegetation to cropland; (iii) NT for 10 years (NT-10); (iv) NT for 20 years (NT-20); (v) NT for 22 years (NT-22); (vi) conventional tillage for 22 years (CT-22). Soil samples were collected from four depths (0–5 cm; 5–10 cm; 10–20 cm; 20–40 cm layer) and soil parameters comprised by SOM pools [i.e., C, N, S, particulate organic C (POC), particulate N (PN), stable C (SC) and stable N (SN), microbial biomass C (MBC) and microbial biomass N (MBN), basal respiration (BR), dissolved organic C (DOC), total polysaccharides (TP) and labile polysaccharides (LP)] were measured. In undisturbed NF soil, the SR of all parameters increased with increase in soil depth. In contrast, the SR decreased in PT, and the SOM was uniformly distributed in the soil profile. All NT treatments restored the SR, and were characterized with higher values of all measured parameters compared to NF. The SR for SOC ranged from 1.12 to 1.51 for CT-22 compared with 1.64–2.61 SR for NT surface and sub-soil layers, respectively. The SR for POC and PN were higher than those for stable C and N. However, SR for the biological pools (e.g., MBC, MBN and BR) were the highest and strongly correlated with the rate of SOC sequestration. An increase in SR of SOC was also positively correlated with the rate and amount of SOC sequestered. Regression analyses indicated a strong correlation between SR of SOC and all parameters monitored in this study. The data showed that the SR of SOC is an efficient indicator of C sequestration in long-term NT management.

Muitos solos tropicais com grau avançado de intemperismo, apesar de apresentarem teores totais de P relativamente elevados, mostram-se deficientes em P disponível, pela baixa solubilidade das principais formas de P encontradas. Neste trabalho, estudou-se o processo de adsorção de P em solos desenvolvidos de rochas vulcânicas básicas e ultrabásicas do Alto Paranaíba em Minas Gerais, algumas das quais ricas em apatita, estabelecendo-se relações com atributos de solo, como superfície específica (SE) e mineralogia. Foram estudados onze horizontes B diagnósticos de perfis de solos da região, por meio de análises químicas, físicas e mineralógicas; foram determinadas as capacidades máximas de adsorção do fósforo (CMAF), SE pelo método direto BET-N2 e indiretamente por cálculos, bem como foi feita a quantificação dos minerais de argila pelo método de alocação. Os valores da SE obtidos indiretamente de cada mineral, foram superestimados em relação à SE determinada pelo método BET-N2 na fração argila total. Nos Latossolos estudados, com texturas e materiais de origem variáveis, desde rochas básico-alcalinas até ultrabásicas, a proporção e a área superficial da gibbsita e goethita têm participação destacada na adsorção de P. A faixa de valores de CMAF TFSA encontrada está consistente com os valores na literatura reportados para Latossolos, embora os valores de CMAF TFSA e CMAF ARG corrigida, de 2,98 e 4,38 mg g-1, respectivamente, do Latossolo Vermelho-Amarelo de rocha ultrabásica (P6), sejam comparáveis àqueles de solos subtropicais alofânicos derivados de cinzas vulcânicas. A CMAF ARG corrigida para percentagem de argila evidenciou expressivos valores nos Cambissolos de rochas vulcânicas ultrabásicas (4,32 e 5,52), com valor menor naquele derivado do tufito (3,16 mg g-1). Os valores de substituição isomórfica de Al na goethita são mais elevados que nas hematitas. Em contraste com os Latossolos, os Cambissolos mostraram variações grandes nos atributos químicos, mineralógicos e na CMAF, em virtude da natureza diversificada de materiais de origem e do menor grau de intemperismo. Despite relatively high levels of total P, most deeply-weathered tropical soils have very low levels of available P due to the low solubility of most P forms found in these soils. In this research we studied P adsorption of soils, some of which were rich in apatite, developed from basic to ultrabasic volcanic rocks in the Upper Paranaíba region of Minas Gerais State, in relation to the specific surface and clay mineralogy. Samples of eleven B horizons from representative Latosols (Oxisols) and Cambisols (Inceptisols) were used. Standard chemical, physical, and mineralogical characterizations were realized, as well as the determination of maximum P adsorption capacity (PMAC), specific surface (SS) by the BET-N2 and indirect methods, and the quantification of individual clay minerals by allocation. The sum of the SS values obtained by the indirect method for each mineral overestimated the results, compared with the SS values obtained by the BET-N2 method for the total clay fraction. Among the studied Latosols, exhibiting varying textures and basic-alkaline to ultrabasic parent materials, the proportion and surface area of gibbsite and goethite appeared closely related to P adsorption. The range of PMAC values for the fine earth (< 2 mm) fraction was also consistent with values reported in literature, although the Red-Yellow Latosol derived from ultrabasic rock (fine earth PMAC = 2.98 mg g-1 and PMACclay = 4.38 mg g-1) was similar to values of alophanic subtropical soils derived from volcanic ash. The PMACclay values were greater in the Cambisols derived from ultrabasic volcanics (4.32 and 5.52) than in those derived from tuffites (3.16 mg g-1). Al-isomorphic substitution in goethites was found to be higher than in hematites. In contrast to the Latosols, the Cambisols presented larger variations in chemical and mineralogical attributes, as well as in PMAC values; this is attributed to their varied parent materials and lower weathering degree of the Cambisols.

Little has been published on the diversity and importance of microaggregates in tropical latosols and their chemistry and fertility. This study presents a detailed analytical and submicroscopical characterization of microaggregates in selected Brazilian Latosols, representing all latosols orders, by means of electron microprobe and scanning electron microscopy (SEM) at high magnification. Chemical data for microaggregates were related to selected soil attributes, including P sorption. In these latosols, no chemical/mineralogical gradients exist between the different plasma zones of the aggregates, indicating an absence of physical–chemical microaggregate nucleation. The microgranular structure occurs in all latosol Bw horizons, with varying degrees of organization, from ‘strongly developed’ to ‘moderately developed’, varying from discrete micropeds to weakly defined /coalesced micropeds, the latter forming a massive kaolinitic groundmass. The P adsorption capacity (PAC) of the soil was significantly correlated with Al 2 O 3 in both external and internal aggregate zones, whereas no correlation was found between PAC and SiO 2, and Fe 2 O 3 amounts. The PAC was attributed to both well-crystalline and poorly crystalline Al forms. The EDS/SEM data for the clay plasma are consistent with the results of H 2 SO 4 extraction. Regarding EDS analysis of microaggregates, it is shown that soil thin sections of 18 cm 2 sizes adequately represent the soil composition in deeply weathered, mineralogically monotonous Brazilian latosols. Due to its differential distribution between coarse and fine fractions, Ti amounts obtained by EDS and H 2 SO 4 are poorly correlated. Ti-EDS data of soil plasma only determines microcrystalline anatase whereas Ti–H 2 SO 4 also includes Ti in sand size resistant minerals in the coarse fractions, not selected for EDS analysis in our procedure. The highly weathered latosols studied possess Bw horizons with a pedobiological microgranular structure, whose degree of development and aggregate roundness are influenced by soil mineralogy. At the microaggregate scale, quartz grains, Ti-minerals, charcoal particles, Fe and gibbsite nodules or concretions occur randomly distributed within the clay plasma, as skeletal grains or inclusions.

The objective of this study was to assess the effect of a native anecic species on phosphorus availability in an Oxisol characterised by a low chemical fertility. Experiments were carried out at Carimagua research station in a representative site of the isohyperthermic savannas on the Colombian Orinoco basin. One field study and two laboratory/incubation studies were performed in a natural herbaceous savanna and a Brachiaria decumbens and Pueraria phaseoloides pasture. In the laboratory, experiment pots were prepared containing soil collected from the respective field paddock's topsoil. Total P content was higher in earthworm casts than in the surrounding soil in field samples, 50% in native savanna soil and more than 100% in pasture soil. In casts produced under laboratory conditions this increase was relatively low (10–20%). Under field conditions, almost without exception, all P fractions were increased in casts relative to the original soil (corresponding to the increase in total P content), being relatively greater in the labile inorganic P fractions. In addition, samples from the natural savanna showed that pH of casts was higher (5.2) than that of soil (4.6) in both field and laboratory samples. Except in the native savanna under field conditions, the phosphatase activity was reduced in casts by 16.7 to 44%. From our results we conclude that earthworms in the field incorporate P from litter or other organic sources (i.e. undecomposed plant and root material, earthworm faeces) which is not normally measured in the analysis of bulk soil., We thank the staff at Carimagua station for their friendship and invaluable help during field work, G. Borrero and M. Rodrı́guez (CIAT) for their technical assistance with the phosphorus fractionations. We are grateful to I. Rao (CIAT), P. Lavelle (IRD, France) and M. Brossard (IRD-EMBRAPA Brazil) for their comments, criticism and useful recommendations made on a previous version of this manuscript. Thanks to R. Thomas (CIAT) for English revision. Andrés F. Rangel is acknowledged for his help during fieldwork while doing his own research and A. Feijoo for his comments and support given to one of the coauthors. We are also deeply appreciated to two anonymous referees for their suggestions that helped us improve this article.

In order to better understand the dynamics of soil organic matter (SOM) in Oxisols and the impact of converting native cerrado (savannah) into pasture, we studied the dynamics of different physically separated SOM pools at different depths in a cerrado oxisol (Typic Haplustox), under natural conditions and after 23 years of cultivated pasture (Brachiaria spp.) via the replacement of the native C (C3-derived) by pasture C (C4-derived). Organic C stocks of the original cerrado (15±3 kg m−2) and pasture (17±3 kg m−2) were not significantly different, which was attributed to the high biomass production of the tropical grasses and the protective effect of the high clay content (>800 g kg−2). We observed that 89–91% of the total organic C accumulated in the clay+silt fraction. The replacement of cerrado-derived C by pasture-derived C was in average 36%, 34%, and 19% for Ap, AB1, and Bw2 horizons, respectively, suggesting a fast turnover rate of organic C regardless of the high clay content. The replacement decreased in the order: free low-density organic matter (LDOM)>heavy fractions (sand, silt, clay)>occluded-LDOM. The lower replacement of the occluded-LDOM compared to the heavy fractions was attributed to protection inside aggregates and to a possible accumulation of C3-derived charcoal (black carbon). After 23 years of pasture, about 50% of the total organic C in the free-LDOM in the topsoil was still from cerrado, indicating that a significant part of this fraction was relatively recalcitrant. Charcoal fragments observed in the fraction suggested that the recalcitrance was probably due to charred material.

The characteristic strong aggregation observed in Oxisols is usually attributed to the presence of free aluminium or iron compounds. Previous investigation of Oxisols from Minas Gerais, Brazil, suggested that iron oxide minerals do not necessarily play a role in aggregation. Oxisol profiles developed on different parent materials (rock-saprolites and sediments), and with different degrees of polygenesis, were investigated to assess whether the physical makeup, rather than the iron content, determines aggregation. Oxisols were investigated by means of micromorphology and laser diffraction grain-sizing. Grain-size distribution curves were determined after three pre-treatments: shaking with water; removal of organic matter; and removal of organic matter followed by deferration. Micromorphology indicated that soils developed on rock-saprolites have hematite droplets (discrete, red colored, equidimensional concentrations) in the saprolite, whereas droplets are not found in soils on Tertiary sediments. However, secondary iron accumulations related to periodic water saturation are encountered in the soils on sediments and not in the soils on rock-saprolites. Grain-size distribution curves showed that the Oxisols on rock-saprolites do not have strong aggregation because of iron oxides alone. Conversely, aggregation by iron oxides is evident in the Oxisols on sediments. This indicates that remobilization of iron during soil formation is essential for iron forms to play a role in aggregation. These findings suggest that the mode of formation and iron mineralogy affect aggregation.

Metadata only record The adverse effect of soil acidity on plant growth and yield, and the scarcity of commercial agricultural lime (CaCO3) in Burundi necessitated a search for alternative liming materials. Thus, the liming potential of locally-made composts was evaluated in a greenhouse experiment, using an acid Oxisol with sorghum (Sorghum vulgaris) as a test plant. Application rates were 10 g/kg (approximately 20 ton/ha) for the composts and 0, 0.85 and 1.70 g/kg for Verrundi lime. Results showed that the application of lime increased plant growth by reducing exchangeable Al, and by increasing soil pH and available P. So did the composts, which were more effective in correcting soil acidity when they were fresh and enriched with some nutrients during the composting process. Apparently, organic molecules produced by the composts helped to chelate and/ or precipitate Al, making the soil more suitable for plant growth. Specifically, an application of 20 ton/ha of composts was equivalent to 0.6- 1.7 ton CaCO3/ha, depending on the compost quality.

Oxisols derived from clayey sediments, sandstone, mafic rocks and schist were sampled in the “Triangulo Mineiro” region, Minas Gerais State, Brazil, to study the relationship between the phosphate adsorption and mineralogy and specific surface area. The specific surface area of the iron oxides estimated from N2 adsorption by the soil clays before and after dithionite-citrate dissolution of the Fe-oxides ranged from 45 to 110 m2 g−1. Specific surface area of the iron oxides correlated to the goethite: goethite +hematite ratio (r = 0.694∗). Specific surface area estimated by differential X-ray analysis did not show good agreement with BET-N2 adsorption values. Phosphate adsorption maxima for the soil clays (< 2 μm) ranged from about 70 to 160 μmol P g−1 of clay. Stepwise regression analysis showed phosphate adsorption for the total clays to be primarily related to goethite, gibbsite, the sum of Fe plus Al oxides and also amorphous Al oxides. A mild treatment for concentrating the soil iron oxides showed small effect in the phosphate adsorption for most soils. It showed the importance of gibbsite and crystalline Fe-oxides in the adsorption, with goethite explaining most of the variation occurring in P adsorption after the treatment. Correlation studies showed the adsorption capacity per unit specific surface to be somewhat dependent on variations in the iron oxide mineralogy of the clay samples. Clay color showed good correlation to the goethites: (goethite + hematite) ratio in soils but no direct relationship between phosphate adsorption and clay color was detected.

Metadata only record Liming values of calcium carbonate (CaCO3) and cowpea green manure were evaluated on an acid Oxisol (Typic Acrorthox, Togitogiga series), based on seed yield and tissue composition of sweet corn (Zea mays), and soil chemical properties. Application rates were 0, 5, and 10 Mg/ha for CaCO3 and 0, 7.5, and 15 Mg/ha for the green manure, factorially arranged. Treatments with commercial NPK fertilizers were included for comparison. Growth and yield of sweet corn showed that soil acidity can be corrected by either lime or green manure additions. Both lime and manure raised soil pH and (modified Truog) extractable phosphorus (P), which were partially responsible for yield increases. Green manuring significantly increased plant P and potassium (K) concentrations, which explain why the manure was more effective than lime in increasing corn yield. Ear leaves sampled at tasseling required at least 0.25% P and 2.4% K to attain >90% of the maximum seed yield.

The Oxisols of the Cerrado region have a simple mineralogy, and are composed mainly of kaolinite and iron and aluminium oxides. The aim of this work was to perform a sequential extraction of iron and aluminium and to relate them to texture, mineralogy and organic carbon in Oxisols of the Cerrado region. The soil samples, 35 in total, were taken from the 0-20 cm layer in Oxisols under pasture located in the Brazilian Cerrado Region. The levels of iron and aluminum extracted by full attack, dithionite-citrate-bicarbonate, ammonium oxalate and sodium pyrophosphate were analyzed according to the textural classes using the Kruskal-Wallis nonparametric test. Then these data were related to the mineralogy and organic carbon through a principal component analysis. Whatever the textures, iron oxides of high degree of crystallinity were the main form of iron and are positively correlated with the iron total content. The aluminum oxides have a high affinity to organic carbon than iron oxides. The levels of iron and aluminum extracted by sodium pyrophosphate were closely related to soil pH.

Pastures cover nearly 50 million hectares in the Cerrado region. The Oxisols, which cover approximately half this area, are highly weathered soils composed mainly of kaolinite, iron and aluminum oxides. Iron and aluminum oxides have a great influence on the retention of phosphorus (P) in these soils. The aim of this study was to quantify the total phosphorus levels, as well as P availability and retention in Oxisols under pasture in the Cerrado region and to relate the data with soil mineralogical, textural and chemical characteristics. The relations between the studied parameters were analyzed by principal component analysis and linear correlation analysis. The ion-exchange resin extractable P was negatively correlated with mineralogical and texture soil characteristics, and positively with soil organic matter contents. Both the total free and the poorly crystalline oxides were negatively correlated with equilibrium P (Prem). Gibbsite, goethite as well as the total free and poorly crystalline oxides were negatively correlated with Prem, indicating their effects on P adsorption to Cerrado Oxisols. Conversely, kaolinite was not significantly correlated with Prem. The negative correlation between Prem and total carbon (C total) was due to the linear increase of soil carbon with the clay and silt contents. The iron and aluminum oxides were the characteristics that most influenced Prem of Cerrado Oxisols.

The objective of this work was to describe the total and available Cu, Fe, Mn and Zn contents, and their relation with the oxisols acidity, fertility, texture and mineralogy under Cerrado pastures. The soil samples were taken from three regions: along the highways GO-060 and BR-154, between the towns of Goiania, GO, and Barra do Garcas, MT; in the northeast of the State of Minas Gerais, in the towns of Unai and Paracatu, MG; and in the Federal District. Fifty-four soil samples were collected from the 0-20 cm layer. Available quantities of Cu, Fe, Mn and Zn (DTPA extracted) were related to: total contents, chemical variables, soils texture and mineralogy, through the analysis of the principal components. The available and total Cu, Fe, Mn and Zn content varied greatly. The availability of Fe, Cu and Mn related mainly to the crystalline iron and pH in water. The availability of Zn was mainly related to the soil exchange capacity. Zn was considered the most frequent limiting micronutrient for Cerrado pasture development.