Responses of tomato hybrid cultivars to soil application of humic acid under greenhouse conditions

Abstract Responses of three tomato (Lycopersicon esculentum Mill.) hybrids viz. 'Luanova', 'Savarona' and 'Tessera' to various doses (0, 0.5, 1.0, 1.5 and 2.0 g L-1) of soil application of humic acid (HA) were evaluated in terms of plant growth, productivity and quality of fruits, under greenhouse conditions, during 2011-12 and 2012-13. In addition to improved quality characteristics, higher values for yield and yield components were recorded for tomato fruits harvested from plants of 'Tessera' cultivar compared to those harvested from other hybrids tested, regardless of growing seasons. Plants from 'Luanova' cultivar were, however, earlier in fruiting with higher number of fruits per plant. Soil application of HA presented positive effects on yield and physicochemical quality of tomato fruits irrespective of the dose of HA and the cultivar investigated, in both seasons. Soil application of HA at higher dose 1.5 g L-1 exhibited better results in all the three tomato cultivars tested, in terms of their vegetative and reproductive growth, and significantly improved the physicochemical quality of their fruits. Conclusively, the tomato hybrid 'Tessera' was found suitable for cultivation under greenhouse conditions while soil application of aqueous solution of HA @ 1.5 g L-1 substantially resulted in higher production of quality tomato fruits.

Resumo Respostas de três híbridos de tomate (Lycopersicon esculentum Mill.) viz. 'Luanova', 'Savarona' e 'Tessera' para várias doses (0, 0,5, 1,0, 1,5 e 2,0 g L-1) de aplicação de ácido húmico (AH) no solo foram avaliadas em termos de crescimento da planta, produtividade e qualidade de frutas, em casa de vegetação, durante 2011-12 e 2012-13. Além das características de qualidade melhoradas, valores mais elevados para o rendimento e os componentes do rendimento foram registrados para frutos de tomate colhidos de plantas do cultivar 'Tessera' em comparação com aqueles colhidos de outros híbridos testados, independentemente das estações de cultivo. As plantas do cultivar 'Luanova', no entanto, frutificaram mais cedo com maior número de frutos por planta. A aplicação de AH no solo apresentou efeitos positivos sobre a produtividade e a qualidade físico-química dos frutos de tomate, independentemente da dose de AH e do cultivar investigado, nas duas safras. A aplicação de HA no solo na dose maior de 1,5 g L-1 apresentou melhores resultados nos três cultivares de tomate testados, quanto ao crescimento vegetativo e reprodutivo, e melhorou significativamente a qualidade físico-química dos frutos. Conclusivamente, o híbrido de tomate 'Tessera' foi considerado adequado para cultivo em casa de vegetação, enquanto a aplicação no solo de solução aquosa de HA @ 1,5 g L-1 resultou substancialmente em maior produção de frutos de tomate de qualidade.

Optimization of Soil DNA Extraction Protocol Using Na2EDTA, SDS, Heating, Vortexing and CaCl2 and Its Validation for Metagenomic Studies

Aim: Several methods described previously for isolation and purification of soil DNA. Most of these protocols use combination of techniques or methods but the role and contribution of each individual method or component used is not clearly discussed. This study aims at analysing the effect of individual components used in extraction of DNA from soil and finally to optimize soil DNA isolation protocol and its validation by using 16SrDNA sequence analysis. Methods and Results: The soil was washed with anionic buffers before lysis step to reduce humic substances and release microbial cells from soil matrix, then the cells were lysed using combination of SDS, heating and vortexing and finally humic substances were removed using chemical flocculation. Pre-lysis washing of soil with 100 mmol l-1 Na2EDTA proved good for releasing microbial cells from soil matrix. Heating the soil sample at 75°C yielded good quantity (15.73 µg g-1 soil) DNA followed by 2% SDS (10.28 µg g-1 soil) and vortexing at 1400 rpm (8.94 µg g-1 soil). Combination of heating, SDS and vortexing yielded 25 µg DNA per gram of soil. Different concentrations of chemical flocculants like AlNH4(SO4)2, FeCl3, CaCl2 and MgCl2 were used to reduce humic substances. Flocculation with 100 mmol l-1 CaCl2 removed 5.2 mg humic substances without significant loss of DNA. 16S rDNA sequence analysis of DNA extracted from soil reveals presence of all the common soil bacterial species indicating the protocol is unbiased. Conclusion: Combination of chemical (SDS) and physical (heating and vortexing) methods yield good DNA whereas addition of enzyme (lysozyme) did not show significant effect on cell lysis. The digestion of isolated DNA with restriction enzyme and amplification of 16S rDNA using Taq DNA polymerase indicates the isolated DNA is pure enough for metagnomic analysis. 16Sr DNA sequencing of soil DNA indicates that this protocol can extract good quality and quantity DNA from range of bacteria present in soil varying in their cell wall composition. The optimised protocol is unbiased, very simple, does not need special equipments and many samples can be processed simultaneously.

Recalcitrant carbon and nitrogen in agriculture soi ls with residue accumulation and fertilization under tropical conditions / Carbono recalcitrante e nitrogênio em solos com acumulação e fertilização de resíduos em condições tropicais

Soil organic matter has a strong relation to total organic carbon, and about 85% of organic carbon consists of humic substances (HS), classified as humin (HU), humic (HA) and fulvic acids (FA), and denominated as recalcitrant carbon in soil. HS are formed by complex, heterogeneous and polydisperse molecules, which have significant influence on the soil physical and chemical characteristics. The study evaluates the hypothesis that agricultural soils treated with organic residues may present higher carbon stocks as presented in forest soils. The aim of this study was to evaluate alterations in recalcitrant carbon and nitrogen stocks in Oxisol (Forest - FL, unfertilized Brachiaria - UB, and fertilized Brachiaria - FB) and Cambisol (Forest - FC, Coastcross - CC, sugarcane - CA, and silage corn - SM) at surface (0.0 - 0.1) and subsurface (0.1 - 0.2 m), in the Zona da Mata in Minas Gerais state, Brazil. Result shows that fertilization, low soil disturbance and residual removal promoted increase of C and N content in HS, being close to native forests. Both, carbon and nitrogen recalcitrant, presented reduction with soil depth. HU ranged from 10.5 to 16.7 g kg-1 and presented the highest concentration compared to FA and HA. In Oxisol, FL and FB presented the highest SH concentration and demonstrate the positive effect of fertilization on carbon stocks improving soil quality in well-managed and productive areas. While, In Cambisol, FC and CC presented higher carbon and nitrogen in HS, mainly for HU and HA fractions, and SM showed the lowest concentrations in all fractions. Our results suggest that soil managements with lower soil disturbance and residual removal promotes increasing of carbon and nitrogen in recalcitrant fraction, with concentration close to native forests. Pasture should be fertilized to improve recalcitrant carbon and nitrogen stocks, avoiding process of degradation in tropical soil. It is an important outcome due to high levels of degraded areas in Brazil caused by inadequate use of soil mainly with pasture.

A matéria orgânica do solo tem uma forte relação com o carbono orgânico total, cerca de 85% do carbono orgânico é composto por substâncias húmicas (HS), classificadas como humina (HU), ácidos húmicos (HA) e fúlvicos (FA), denominadas como carbono recalcitrante no solo. As HS são formadas por moléculas complexas, heterogêneas e polidispersas, que exercem influência significativa nas características físicas e químicas do solo. O estudo avalia a hipótese de que solos agrícolas tratados com resíduos orgânicos podem apresentar maiores estoques de carbono como os encontrados em solos florestais. O objetivo destetrabalho foi avaliar as alterações nos estoques de carbono e nitrogênio recalcitrantes em Latossolo (Floresta - FL, Brachiaria não fertilizada ­ UB, e Brachiaria fertilizada - FB) e Cambissolo (Floresta - FC, coastcross - CC, cana-de-açúcar e milho para silagem - SM) na superfície (0,0 - 0,1) e sub-superfície (0,1 - 0,2 m), na Zona da Mata em Minas Gerais, Brasil. Os resultados mostram que a adubação, a baixa perturbação do solo e a remoção dos resíduos promoveram aumento do teor de C e N na HS, estando próximos às florestas nativas. Ambos, carbono e nitrogênio recalcitrantes, apresentaram redução com a profundidade do solo. A HU variou de 10,5 a 16,7 g kg-1 e apresentou a maior concentração em relação à FA e HA. Em Latossolo, FL e FB apresentaram a maior concentração de SH e demonstraram o efeito positivo da adubação nos estoques de carbono, melhorando a qualidade do solo em áreas bem manejadas e produtivas. Enquanto, no Cambissolo, FC e CC apresentarammaiores teores de carbono e nitrogênio nas HS, principalmente nas frações HU e HA, e SM apresentou as menores concentrações em todas as frações. Nossos resultados mostram que manejos de solo com menor perturbação e remoção de resíduos promovem o aumento de carbono e nitrogênio em frações recalcitrantes, com concentração próxima às florestas nativas. A pastagem deve ser fertilizada para melhorar o estoque de carbono e nitrogênio recalcitrante, evitando o processo de degradação do solo tropical. Este é um resultado importante devido aos altos níveis de áreas degradadas no Brasil causadas pelo uso inadequado do solo,principalmente com pastagens.

Progress of antitumor mechanisms of humic acids / 肿瘤研究与临床

Humic acids, a complex macromolecular organic carbon resources, contain different functional groups such as quinones, phenols, carboxylic acids, hydroxyl, and aromatic structures. The various functions and pharmacological activities are mainly attributable to the different functional groups of humic acids. In recent years, studies show that antitumor effect of humic acids can be analyzed from activation of immune system, induction of cell injury and apoptosis, photothermal reaction, or binding with other materials. This paper reviews the progress of antitumor mechanisms of humic acids.

Adsorption and availability of phosphorus in response to humic acid rates in soils limed with CaCO3 or MgCO3 / Adsorção e disponibilidade de fósforo em resposta a doses de ácido húmico em solos corrigidos por CaCO3 ou MgCO3

ABSTRACT Humic acid (HA) may reduce adsorption and increase soil P availability, however, the magnitude of this effect is different when Ca2+ prevails over Mg2+ in limed soils. The objective of this study was to evaluate the effects of HA rates and carbonate sources on the adsorption, phosphate maximum buffering capacity (PMBC), and P availability in two contrasting soils. Oxisol and Entisol samples were firstly incubated with the following HA rates: 0, 20, 50, 100, 200 and 400 mg kg-1, combined with CaCO3 or MgCO3, to evaluate P adsorption. In sequence, soil samples were newly incubated with P (400 mg kg-1) to evaluate P availability. The least P adsorption was found when 296 mg kg-1 of HA was added to Oxisol. Applying HA rates decreased maximum adsorption capacity, increased P binding energy to soil colloids and did not alter PMBC of Entisol. Available P contents in Oxisol increased with HA rates, but it did not change in Entisol. Choosing the right HA rate can decrease PMBC up to 40% and increase the Oxisol P availability by 17%. Application of MgCO3 instead of CaCO3 decreased P adsorption in both soils. Thus, a positive correlation between Ca2+ content and PMBC was verified. Optimum rate of HA and the preponderance of Mg2+ instead of Ca2+ in soil volume fertilized with P are effective practices to reduce adsorption and increase P availability, especially in clayey Oxisol.

RESUMO O ácido húmico (AH) pode reduzir a adsorção e aumentar a disponibilidade de P nos solos, entretanto, a magnitude desse efeito é diferente quando o Ca2+ prevalece sobre Mg2+ em solos com acidez corrigida. Objetivou-se avaliar os efeitos de doses de AH e fontes de carbonato na adsorção, fator capacidade de P máximo (FCPm) e disponibilidade de P em solos contrastantes. Amostras de Latossolo e Gleissolo foram primeiramente incubadas com as seguintes doses de AH: 0, 20, 50, 100, 200 e 400 mg kg-1, combinadas com CaCO3 ou MgCO3, para avaliar a adsorção de P. Em sequência, as amostras de solo foram novamente incubadas com P (400 mg kg-1), para determinar a disponibilidade de P. A aplicação de doses de AH reduziu a capacidade máxima de adsorção, aumentou a energia de ligação do P e não alterou a FCPm do Gleissolo. O teor de P disponível aumentou com o acréscimo das doses de AH no Latossolo, contudo, não foram alterados no Gleissolo. A escolha correta da dose de AH reduziu a FCPm em até 40% e aumentou a disponibilidade de P no Latossolo em 17%. A aplicação de MgCO3 em vez do CaCO3 reduziu a adsorção de P em ambos os solos. Assim, houve correlação positiva entre o teor de Ca2+ e a FCPm. A dose ótima de AH e a predominância de Mg2+ sobre Ca2+ no volume de solo adubado com P são práticas efetivas para reduzir a adsorção e aumentar a disponibilidade de P, especialmente, no Latossolo argiloso.

Application of Multiple Displacement Amplification in Samples with Inhibitors / 法医学杂志

OBJECTIVES@#To explore the ability of inhibition resistibility of multiple displacement amplification （MDA） in samples with inhibitors. To explain the application and value of MDA in forensic medicine by comparing with using magnetic beads methods （MBM） to purify sample.@*METHODS@#Different concentrations of hemoglobin and humid acid （HA） mixed with DNA samples and then divided the samples into MDA group, MBM group and control group. D3S1358 locus was amplified and detected by polyacrylamide gel electrophoresis detection system and AmpFℓSTR® Identifiler™ Plus Kit-capillary electrophoresis detection system.@*RESULTS@#When hemoglobin concentrations exceed 1 ng/μL or HA concentrations exceed 0.1 ng/μL, amplification products could not be obtained by single-locus system in control group. When hemoglobin concentration exceeds 100 ng/μL or HA concentrations exceed 1 ng/μL, the samples could not be amplified by MBM. Inhibitors in different concentrations were amplified successfully in MDA group without any influence from inhibitors.@*CONCLUSIONS@#MDA has the capability to remove the inhibition of hemoglobin and HA, which is better than MBM and has a certain value in forensic practices.

Application of Multiple Displacement Amplification in Samples with Inhibitors / 法医学杂志

ObjectiveTo explore the ability of inhibition resistibility of multiple displacement amplification (MDA)in samples with inhibitors. To explain the application and value of MDA in forensic medicine by comparing with using magnetic beads methods(MBM)to purify sample.MethodsDifferent concentra-tions of hemoglobin and humid acid(HA)mixed with DNA samples and then divided the samples into MDA group, MBM group and control group.D3S1358locus was amplified and detected by polyacry-lamide gel electrophoresis detection system and AmpF?STR? IdentifilerTM Plus Kit-capillary electrophore-sis detection system.ResultsWhen hemoglobin concentrations exceed 1 ng/μL or HA concentrations ex-ceed 0.1 ng/μL, amplification products could not be obtained by single-locus system in control group. When hemoglobin concentration exceeds 100 ng/μL or HA concentrations exceed 1 ng/μL, the samples could not be amplified by MBM. Inhibitors in different concentrations were amplified successfully in MDA group without any influence from inhibitors.ConclusionMDA has the capability to remove the inhibi-tion of hemoglobin and HA, which is better than MBM and has a certain value in forensic practices.

Influence of long term application of fertilizers on soil organic matter content.

The soil samples were collected from the soils of Long Term Fertilizer Experiments that have been fertilized for the last 25 years from a) control plot (receiving no fertilizer/FYM); b) plot receiving 100% NPK fertilizer application and c) Plot receiving 100% N in the form of FYM, to study the changes in nature and amount of organic matter and these were compared with a similar adjacent soil under natural vegetation. The soil samples were collected from 0-15 cm (surface) and 15-30 cm (sub surface) layers. The humic substances were fractionated by Tyurins method. The total N and available N content was determined and C/N ratio was calculated. The humic acid was isolated, purified and analyzed for oxygen containing functional groups and spectral properties. It was observed that the soil under natural vegetation had a higher total N while the soil under continuous cultivation had higher available N. The C/N ratio of soil under natural vegetation was high compared to the soil under continuous cultivation. These values were high in surface layers compare to sub surface layers. The oxygen containing functional groups in Humic acid (HA) were high in soil under natural vegetation compared to the soil under continuous cultivation. The total acidity and COOH content of surface layers was high compared to sub surface layers in soils under both situations. Phenolic OH groups of subsurface layer was high in soil under natural vegetation and continuous cultivation indicating that this group in sub surface layers and high potential for interaction with clays and metal ions. The higher contents of total acidity and –COOH groups in soil under natural vegetation could be attributed to the difference in chemical composition and molecular weight of humic substances. The E4/E6 ratios of HA’S were less than 5.0 indicating high degree of condensation of aromatic humic acid. The potentiometric titrations of humic acids with standard 0.1 N NaOH indicated a gradual increase in pH with the addition of base thus indicating a high buffering capacity of humic acid. The potentiometric titration curves were sigmoid in nature indicating an apparent mono basic character and had a single break suggesting weak acidic character of humic acids. The conduct metric titrations of humic acids showed a slow increase in the initial stage followed by a steep increase at later stages. The apparent pKa values calculated from potentiometric titration data using Henderson-Hassebalch equation varied from 5.24 to 5.68.

Effect of humic acid and soil on the dissolution performance of depleted uranium in water / 中华放射医学与防护杂志

Objective To study the effect of humic acid (HA) and soil on dissolution performance of depleted uranium (DU).Methods Using the static dissolve-adsorption experiment and inductively coupled plasma-mass spectrometry(ICP-MS) to determine uranium concentration and 235U/238U isotope ratios of the samples at different time and study the dissolution of DU in water.Results The solubility of DU in water was reduced by 90％ by adding HA.Soil could increase the solubility of DU in water by nearly 25％,adding an appropriate amount of HA could play a supporting role on the dissolution of DU,in this experiment adding 5％ of HA was best.Conclusions Soil and HA could produce positive and negative impact on the solubility of DU in water,and the combined effect of the two relied on the complex absorption and complexation reactions of soil,HA and dissolved uranium ions.

Induction of Systemic Resistance of Benzothiadiazole and Humic Acid in Soybean Plants Against Fusarium Wilt Disease

The ability of benzothiadiazole (BTH) and/or humic acid (HA) used as seed soaking to induce systemic resistance against a pathogenic strain of Fusarium oxysporum was examined in four soybean cultivars under greenhouse conditions. Alone and in combination the inducers were able to protect soybean plants against damping-off and wilt diseases compared with check treatment. These results were confirmed under field conditions in two different locations (Minia and New Valley governorates). The tested treatments significantly reduced damping-off and wilt diseases and increased growth parameters, except the number of branches per plant and also increased seed yield. Application of BTH (0.25 g/L) + HA (4 g/L) was the most potent in this respect. Soybean seed soaking in BTH + HA produced the highest activities of the testes of oxidative enzymes followed by BTH in the four soybean cultivars. HA treatment resulted in the lowest increases of these oxidative enzymes. Similar results were obtained with total phenol but HA increased total phenol more than did BTH in all tested cultivars.

Effects of calcium nitrate and humic acid on pepper seedling growth under saline condition.

This study was carried out in order to determine effects of calcium nitrate and humic acid applications on pepper seedling growth under saline condition. A mixture of soil:sand (1:1) was used as a plant growing media including 90 mg kg-1 P2O5, 180 mg kg-1 K2O and 250 mg kg-1 N. Four different doses of humic acid (0, 1000, 2000 and 4000 mg kg-1) and calcium nitrate (0, 50, 100 and 150 mg kg-1) were applied into the growing media. Before sowing Demre variety pepper seeds, 60 m mol NaCl was added into 300 cm3 soil:sand mixture in each pot. Applications of humic acid and calcium nitrate significantly affected pepper seedling growth. 1000 and 2000 mg kg-1 humic acid and 50 mg kg-1 calcium nitrate applications increased fresh and dry leaf weight, fresh and dry root weight, stem diameter, root length and shoot length. The highest rates of humic acid (4000 mg kg-1) and calcium nitrate (100 and 150 mg kg-1) decreased these criteria of pepper seedling under the saline soil condition.

Efeito dos ácidos húmicos na inoculação de bactérias diazotróficas endofíticas em sementes de milho / Effect of the humic acids in endophytic diazotrophic bacteria inoculation in corn seeds

Os ácidos húmicos podem atuar no aumento da população de bactérias diazotróficas introduzidas no interior da planta e, consequentemente, no incremento dos efeitos benéficos sobre a planta hospedeira. Com este trabalho, objetivou-se avaliar o efeito dos ácidos húmicos na inoculação de bactérias diazotróficas endofíticas, em sementes de milho. Foi utilizada a estirpe Herbaspirillum seropedicae Z67 BR 11175. A inoculação das sementes com as bactérias e a adição de ácidos húmicos foram realizadas pelo recobrimento das sementes de milho UENF 506-8, com a mistura de calcário, meio de cultura semisólido, água e cimentante. As sementes recobertas foram semeadas em vasos Leonard. Aos 40 dias após a semeadura, as plântulas foram coletadas, e foi realizada a contagem de bactérias nas raízes pela técnica do Número Mais Provável. Os resultados deste trabalho mostram que os ácidos húmicos não interferem negativamente no crescimento das bactérias e estimulam a colonização da microbiota nativa. No entanto, nas condições avaliadas, a aplicação conjunta de bactérias + ácidos húmicos não estimulou o crescimento da população de bactérias inoculadas nas plântulas de milho.

The objective of this research was to evaluate the effect of the humic acids in the inoculation of endophytic diazotrophic bacteria in corn seeds. It was used the bacteria Herbaspirillum seropedicae Z67 BR 11175. The inoculation of the seeds with the bacteria and the addition of humic acids were accomplished by the coating of the corn seeds UENF 506-8. The coating was accomplished with a mixture of lime, semi-solid middle culture, water and cement. The seeds covered were sown in Leonard vases. Forty days after sowing the plants were collected and the bacteria couting was accomplished in the roots by the Most probable Number technique. The results showed that the humic acids doesn't interfere negatively in the bacteria growth of and they stimulate the colonization of the native microbiota. However, in the appraised conditions, the united application of bacteria + humic acids didn't stimulate the growth of the bacteria population inoculated in the corn seedling.

Germinação e vigor de sementes de milho recobertas e viabilidade do inóculo durante o armazenamento / Germination and vigor of covered corn seeds and viability of the inoculum during storage

Conduziu-se este trabalho com o objetivo de avaliar a qualidade fisiológica das sementes recobertas com diferentes misturas e armazenadas, assim como a sobrevivência das células bacterianas no recobrimento destas. Utilizou-se neste estudo a estirpe H. seropedicae Z67 BR 11175. O recobrimento das sementes de milho ‘UENF 506-8’ foi realizado com a mistura de calcário, meio de cultura semi-sólido, água e cimentante. As sementes foram acondicionadas durante três meses, em sacos de papel multifoliado e armazenadas em duas condições: ambiente de laboratório (temperatura média de 26,2 ºC e UR média de 61,5%) e câmara BOD. A cada30 dias de armazenamento, foram efetuadas determinações do teor de água, contagem de bactérias e avaliações da qualidade fisiológica das sementes. O recobrimento das sementes não altera a perda natural da qualidade fisiológica das sementes durante o armazenamento. Dentre as condições de armazenamento estudadas, a mais adequada para a manutenção das sementes foi a temperatura média de 26,4 ºC e UR média de 61,5 %. As células bacterianas foram observadas nas raízes das plântulas oriundas de sementes revestidas com bactéria, armazenadas por até 60 dias independente da condição de armazenamento.

The aim of this study was to evaluate the physiological quality of stored seeds covered with different mixtures and the period of survival of the bacterial cells in the seed coatings. H. seropedicae Z67 BR 11175 was used in this study. The ‘UENF 506-8’ corn seeds were coated with a mixture preparation consisting of lime, JNFb semi-solid medium, water and cement. The seeds were conditioned for three months in paper bags and stored under two conditions: laboratory (at a temperature of 26.2 ºC and 61.5% relative humidity) and BOD chamber. Every 30 days of storage determinations of the water content, counting of bacteria, and evaluations of the physiologic quality of the seeds were performed. The coating of the seeds did not modify the natural loss of physiological quality of the seeds during the storage. Among the storage conditions studied, the most appropriate for the maintenance of the seeds was the 26.2 ºC and 61.5% of relative humidity. Bacterial cells were detected in the roots of plants originated from coated seeds inoculated with bacterial and stored up to 60 days independently the of storage conditions.

Efeito da adubação orgânica sobre as frações de carbono de solos cultivados com alfacen americana / Organic fertilizer effects upon carbon fractions from soils cultivated with iceberg lettuce

Avaliou-se, neste estudo, o efeito da aplicação de adubos orgânicos, minerais e calagem, nas frações húmica, fúlvica e nos teores de carbono orgânico de um Latossolo Vermelho e de um Cambissolo, cultivados com alface (americana). O experimento, realizado no Departamento de Ciência do Solo da Universidade Federal de Lavras, foi constituído de cinco doses de material húmico (0, 20, 40, 100 e 200 L ha-1), três tipos de adubação (composto orgânico, esterco de aves e mineral) e calagem (com e sem uso de calcário), em cinco repetições. No Cambissolo, a calagem contribuiu para a diminuição do teor de C orgânico nas áreas adubadas com fertilizante mineral e composto, e aumentou o armazenamento de C no solo adubado com esterco de aves. Em relação à adubação mineral, o uso de adubo orgânico aumentou os teores de C-fração ácido húmico e a relação C-húmico/fúlvico. No Latossolo, independente do tipo de adubação, o uso da calagem propiciou o armazenamento no solo de mais C do que o observado na área sem correção da acidez. Os efeitos da calagem e das fontes de nutrientes variaram em função da fração orgânica analisada ou das relações entre seus teores de carbono.

This study evaluated the effects of organic and mineral fertilizers and liming, on humic, fulvic, and organic carbon fractions of an Inceptisol and an Oxisol grown with lettuce. The experiment was carried out at the Soil Science Department of Federal University of Lavras, Minas Gerais state, Brazil. It was performed with 5 levels of soil conditioner (0, 20, 40, 100, 200 L ha-1), 3 fertilizers (organic compost, chicken manure and mineral), and liming (present or absent) using five replications. In the Inceptisol essay, the liming contributed to a decrease in the organic-C content in the mineral and compost fertilized plots, and increased C-accumulation in the treatments under chicken manure. The organic fertilizer increased the content of C-humic acid and the relation Chumic/fulvic. In the Oxisol essay, the liming contributed to C-accumulation when related to the treatments without liming. Liming effects and fertilizers varied as a function of the analyzed organic fractions and C content.

Caracterizacióndde ácidos húmicos y fúlvicos de un mollisol bajo dos coberturas difreentes / Charaterization of humic and fulvic acids from a mollisol under two diferent coverlands

Para evaluar y comparar algunas propiedades de los ácidos húmicos (AH) y fúlvicos (AF) como el grado de condensación y polimerización, el contenido total de carbono, hidrógeno y nitrógeno, y sus constantes de acidez, se analizó la fracción menor a 50 µm de un Mollisol del horizonte Ap, bajo caña de azúcar, y se comparó con un horizonte A, bajo bosque. Para tal fin se hicieron extracciones sucesivas con tetraborato de sodio 0,05 M, pirofosfato de sodio 0,025 M e hidróxido de sodio 0,1M. Las sustancias húmicas se purificaron mediante tratamientos con ácidos inorgánicos en solución al 1% de HCl y HF, resinas de absorción Amberlita XAD-16 e intercambio catiónico R101H+, diálisis y liofilización, y se caracterizaron por análisis elemental, relación E4/E6 y potenciometría ácido-base de acuerdo con las funciones de Gran modificadas. La relación E4/E6 permitió establecer mayores tamaños moleculares y grado de condensación de los ácidos húmicos en relación con los ácidos fúlvicos. Por potenciometría ácido-base se determinaron, en los ácidos húmicos y ácidos fúlvicos, las concentraciones de grupos funcionales ácidos y sus respectivas constantes de acidez. Dos de éstas, tituladas entre pH 4,0 y 6,1 corresponden a grupos carboxílicos, las otras dos entre pH 7,2 y 8,7 son el resultado de grupos -OH fenólicos fuertes y carboxílicos débiles. En el horizonte Ap, bajo caña de azúcar, los resultados demostraron que las prácticas de uso y manejo de este cultivo han llevado a la homogeneización de las sustancias húmicas, mientras que en el horizonte A bajo bosque existen ácidos húmicos y fúlvicos diferenciados por tamaño molecular, aromaticidad y grado de humificación.

In order to determine and to compare some physicochemical properties of humic (HA) and fulvic (FA) acids such as degree of condensation and polymerization, the total C,H,N content and pKa values were analyzed in the smaller fraction (< 50 m) from Ap horizon under sugarcane crop in opposition to A horizon under forest, both Mollisol order. To carry out this aim, successive extractions with sodium tetraborate 0.05 M, sodium pyrophosphate 0.025 M, and sodium hydroxide 0.1 M were made. The purification of these humic substances by treatment with inorganic acids 1% solutions of HCl and HF, Amberlite XAD-16 adsorption resin and R 101H+ cationic exchange, dialysis and freeze driying were done. The humic and fulvic acids were characterized by elemental analysis, E4/E6 relation and acid-base potentiometry. The ratio E4/E6 allows to establish that molecular size and degree of condensation in humic acids were bigger than in fulvic acids. By means of acid-base potentiometry, the concentrations of functional acid groups and their acid constants in the humic and fulvic acids were determined. Four constants were found; first and second between pH 4.0 and 6.1 correspond to differents kinds of carboxyl groups and another two between pH 7.2 and 8.7 come from strong O-H phenolic and weak carboxyl groups. In the Ap horizon under sugarcane the characterization showed that the handling and land use practices promote the homogeneity of humic substances meanwhile in the A horizon under forest; the humic and fulvic acids are different due to their degree of condensation molecular size and humification index.