Caracteriza����o e classifica����o de gleissolos da v��rzea do rio Solim��es (Manacapuru e Iranduba), Amazonas, Brasil

As v��rzeas do rio Solim��es s��o ��reas inund��veis com predom��nio de Gleissolos, onde se estabeleceu grande parte da popula����o rural do Estado do Amazonas. Os objetivos deste trabalho foram caracterizar e classificar cinco perfis de Gleissolos, distribu��dos em tr��s ��reas da bacia do M��dio Amazonas, localizados nas v��rzeas dos munic��pios de Manacapuru e Iranduba. Ap��s a descri����o morfol��gica dos solos, coletaram-se amostras dos seus horizontes para caracteriza����o f��sica, qu��mica e mineral��gica. Similarmente, todos os perfis apresentaram expressiva gleiza����o na matriz do solo, com cores cinzenta a cinzenta-esverdeada, nos horizontes mais superficiais, e cinzenta-clara a cinzenta-escura, nos subsuperficiais, denotando a redu����o do ferro. Os teores mais elevados da fra����o areia em horizontes de subsuperf��cie indicaram presen��a de diferentes camadas de deposi����o fluvial, enquanto os elevados teores de silte evidenciaram a natureza sedimentar recente e o baixo grau de desenvolvimento pedogen��tico desses solos. Os c��tions predominantes nos solos foram Ca2+ e Mg2+, que apresentaram porcentagens de s��dio troc��vel (PST), com amplitude de varia����o entre 0,70 e 2,09. Os valores de carbono org��nico encontrados foram menores de 80 g kg-1, apresentando a natureza mineral dos sedimentos rec��m-depositados. A composi����o mineral��gica da fra����o argila revelou presen��a significativa de argilominerais 2:1, mas sem grande variabilidade entre os perfis. Esses resultados refletiram-se em elevada soma e satura����o por bases, caracterizando solos eutr��ficos e com argila de atividade alta.

Caracteriza����o de terras pretas arqueol��gicas no sul do estado do Amazonas

As Terras Pretas Arqueol��gicas (TPAs) s��o unidades de solo que apresentam como caracter��sticas alta fertilidade, colora����o escura e presen��a de fragmentos cer��micos. Sobre a forma����o das TPAs, a hip��tese mais bem aceita entre os pesquisadores �� que essas foram originadas a partir de processos antr��picos provocados pelos homens pr��-colombianos. Diante disso, objetivou-se caracterizar TPAs localizadas nos munic��pios de Apu�� e Manicor��, na regi��o sul do Estado do Amazonas. Foram selecionados sete locais de ocorr��ncia de TPAs, sendo abertas trincheiras e os perfis do solo caracterizados morfologicamente. Procedeu-se �� coleta de amostras de solo em cada horizonte para as seguintes an��lises f��sicas e qu��micas: composi����o granulom��trica, argila dispersa em ��gua, grau de flocula����o, densidade do solo, densidade de part��culas e porosidade total, pH em ��gua e KCl, Ca2+, Mg2+, K+ e Al3+ troc��veis, P dispon��vel, H+Al e C org��nico, al��m dos teores dos ��xidos do ataque sulf��rico, ��xidos livre e formas mal cristalizadas. A textura dos horizontes A antr��picos variaram de franco-arenosa a franco-argilosa. Os fragmentos cer��micos e material l��tico apresentaram-se em quantidades e profundidades semelhantes no horizonte A dos perfis estudados, sugerindo certa similaridade dos fatores antr��picos que promoveram sua forma����o. Os horizontes antr��picos dos perfis P3, P4 e P7 apresentaram car��ter eutr��fico e teores altos a muito altos de f��sforo dispon��vel, quando comparados aos perfis P1, P2, P5 e P6, evidenciando heterogeneidade das TPAs.

Chemical properties and mineralogy of soils with plinthite and petroplinthite in Iranduba (AM), Brazil

Large areas of Plinthosols with ferruginous materials such as plinthite and/or petroplinthite are fairly common in the Brazilian Amazon basin. This work was carried out to investigate the chemical behavior, mineralogical composition and weathering stage of four representative soil profiles with plinthite and petroplinthite, in Iranduba, AM (Central Amazon). Three well-drained soil profiles at high elevations were studied (P1, Plinthic Vetic Ferralsol; P2 and P3, Vetic Endopetric Plinthosol) and a contrasting poorly drained soil (P4 Haplic Plinthosol), located at low elevation. After profile descriptions, soil samples were collected from each horizon, air-dried, sieved (2 mm), and analyzed for particle-size distribution, pH, exchangeable cations (Al3+, Ca2+, Mg2+, K+, and Na+), as well as available P and total organic carbon (TOC) content. The minerals present in the clay and sand fractions, as well as in the ferruginous materials were identified by X-ray Diffraction (XRD). The weathering stage of these soils was assessed by means of Ki and Kr indexes, and the amounts of free and amorphous Fe and Al oxides by using dithionite citrate bicarbonate (DBC) and ammonium oxalate dissolution procedures, respectively. The results showed that all soils were extremely unfertile, with pH levels ranging between strong and moderate acidity, very low sum of bases and organic matter content, and of available P. The mineralogy of the soil profiles was very similar, mainly of the well-drained soils, with predominance of kaolinite and quartz in the clay and sand fractions, respectively. In the poorly-drained P4, 2:1 clay particles were also observed. These profiles can be considered highly developed according to the Ki index, however, the Ki value of P4 was higher, indicating that this soil was less developed than the others. In summary, these profiles with plinthite and petroplinthite can be characterized as highly developed and infertile soils and are, with exception of P4, well-drained.

Doses de gesso em cafeeiro: influ��ncia nos teores de c��lcio, magn��sio, pot��ssio e ph na solu����o de um latossolo vermelho distr��fico

O desbalan��o entre Ca2+, Mg2+ e K+ no solo como consequ��ncia das aplica����es elevadas de gesso deve-se ��s rela����es de tamanho (raio i��nico) e densidades de cargas (rela����o carga/raio) de cada esp��cie i��nica. Quanto maior a densidade de carga, mais intensa ser�� a liga����o i��nica do c��tion com ��ons de cargas opostas como OH- e SO4-2. Dessa maneira, o uso excessivo de gesso agr��cola, sem considerar o balan��o de cargas das part��culas do solo; o equil��brio i��nico; e a CTC podem resultar em expressiva lixivia����o ao longo do perfil do solo. O objetivo deste estudo foi avaliar o efeito de elevadas doses de gesso (0, 7 e 56 t ha-1) nos teores de Ca2+, Mg2+, K+ e pH na solu����o de um Latossolo Vermelho distr��fico cultivado com cafeeiro, obtida pelo m��todo adaptado do extrato aquoso. O solo foi amostrado nas profundidades de 0,15-0,25; 0,35-0,45; 0,75-0,85; 1,15-1,25 e 2,35-2,45 m na linha de plantio, em quatro tratamentos: G-0 - gesso no preparo (aplica����o ocorreu em setembro de 2008, distribu��do a lan��o, na quantidade de 2 t ha-1) e sem gesso na linha de plantio; G-7 - gesso adicionado durante a prepara����o do solo (2 t ha-1), na mesma condi����o do G-0 e 7,0 t ha-1 de gesso na linha de plantio; G-56 - gesso adicionado durante a prepara����o do solo (2 t ha-1), na mesma condi����o do G-0 e 56 t ha-1 de gesso na linha de plantio (nessas parcelas experimentais as entrelinhas de plantio foram cobertas com braqui��ria); e CV-7: aus��ncia de braqui��ria na entrelinha, com gesso no preparo e 7 t ha-1 de gesso na linha, com tr��s repeti����es distribu��das em blocos ao acaso, totalizando 60 amostras. Ap��s 16 meses da adi����o de gesso, observou-se redu����o do pH na solu����o do solo nas profundidades de 0,15-0,25; 0,35-0,45 e 0,75-0,85 m. A aplica����o de gesso agr��cola foi eficiente na melhoria do ambiente radicular no subsolo, aumentou a concentra����o de Mg2+ e Ca2+ na solu����o do solo, mas reduziu o K+ em profundidade, a partir de 0,85 m. Os teores de Ca2+ e Mg2+ troc��veis na solu����o do solo estiveram acima do n��vel cr��tico; entretanto, os teores de K+ troc��vel se mantiveram na faixa do valor cr��tico, indicado para o desenvolvimento da cultura.

Impacto do manejo dos res��duos da colheita, do preparo do solo e da aduba����o na produtividade de eucalipto

Tem sido cada vez maior a preocupa����o das empresas do setor florestal em adotar pr��ticas pautadas na conserva����o do solo e da ��gua. Nesse sentido, este trabalho teve por objetivo avaliar o impacto do manejo dos res��duos da colheita, do preparo do solo e do uso de res��duos industriais, na fertilidade do solo e produtividade de eucalipto. O experimento foi iniciado ap��s o corte raso de um plantio comercial de EUCALYPTUS GRANDIS, onde os res��duos da colheita foram manejados (retirada de todo o res��duo; remo����o da casca e dos galhos com di��metro superior a 3,0 cm; e manuten����o de todos os res��duos na superf��cie do solo). Em seguida, realizaram-se o preparo do solo (com subsolador de uma e tr��s hastes), a aplica����o dos res��duos industriais (res��duo de celulose e cinzas) na superf��cie do solo e o plantio de mudas de EUCALYPTUS GRANDIS X E. UROPHYLLA Foi utilizado o delineamento em blocos ao acaso, contendo oito tratamentos e quatro repeti����es. Os tratamentos consistiram da combina����o dos diferentes tipos de manejo dos res��duos da colheita, preparo do solo e aplica����o dos res��duos industriais. Cada parcela experimental foi composta por cinco linhas com 19 plantas cada. Aos 83 meses ap��s o plantio, foram medidos o DAP (di��metro �� altura do peito) e a altura das ��rvores, para c��lculo do volume de madeira. A fertiliza����o e a manuten����o dos res��duos da colheita florestal elevaram os teores de Ca2+ e Mg2+ troc��veis no solo. A manuten����o total dos res��duos vegetais na ��rea ap��s a colheita resultou em aumento de 71,7 m�� ha-1 de madeira, quando comparado �� remo����o de todos os res��duos. N��o houve diferen��a entre os modos de preparo do solo com subsolador de uma e tr��s hastes, quanto ao volume de madeira. Os maiores volumes de madeira foram obtidos dos tratamentos que receberam as maiores quantidades de res��duo de celulose e cinzas, ao mesmo tempo em que foi mantida parte do res��duo vegetal ap��s a colheita. A aplica����o do res��duo de celulose e cinzas favoreceu a manuten����o e, ou, aumento da produtividade do eucalipto.

Atributos qu��micos do solo associados �� produtividade do trigo em um talh��o com diferentes potenciais produtivos

Potenciais produtivos distintos t��m sido verificados entre talh��es, bem como dentro desses, em ��reas sob muitos anos de plantio direto (PD). Ferramentas de agricultura de precis��o (AP) podem auxiliar a identificar tais diferen��as, mas para manejar eficientemente a fertilidade do solo nessas condi����es a amostragem deve ser representativa. Este trabalho teve como objetivo avaliar a influ��ncia de atributos qu��micos do solo, conforme a camada ou profundidade de amostragem, na produtividade da cultura do trigo, em uma ��rea sob PD de longa dura����o, utilizando zonas de um talh��o com potenciais produtivos distintos. O estudo foi feito em Reserva do Igua��u, PR, em ��rea com 25 anos de PD e cinco anos de ado����o de t��cnicas de AP. A partir de mapas de colheita anteriores, identificaram-se duas zonas, Z1 (alta produtividade) e Z2 (baixa produtividade), onde se estabeleceram malhas com 16 unidades amostrais. A produtividade do trigo foi estimada em tr��s pontos por unidade, coletando-se amostras de solo de 0,0-0,1 e de 0,1-0,2 m nos mesmos pontos. A produtividade do trigo foi 22 % maior em Z1 do que em Z2, de acordo com os mapas de colheita utilizados. Os teores de carbono org��nico do solo (Corg) foram maiores em Z1, nas duas camadas do solo. Na camada de 0,1-0,2 m, a satura����o (m%) e os teores de Al3+ foram significativamente maiores em Z2; nessa camada, Z1 apresentou maiores valores de pH e satura����o por bases (V%) e teores de Ca2+, Mg2+ e K+. Houve correla����o positiva da produtividade com os teores de Corg nas duas camadas do solo. Considerando somente a camada de 0,1-0,2 m, a correla����o foi positiva com os valores de pH e V% e com a disponibilidade de Ca2+, Mg2+ e K+; e negativa, com a disponibilidade de Al3+. As diferen��as na fertilidade do solo entre Z1 e Z2 se deram principalmente na camada de 0,1-0,2 m e foram associadas �� diferen��a de produtividade do trigo, indicando ser importante a presen��a desse estrato na amostragem do solo em ��reas de PD de longa dura����o, visando representar corretamente o estado de fertilidade do solo.

Soil fertility, nutrition and yield of maize and barley with gypsum application on soil surface in no-till

Annual crop yield and nutrition have shown differentiated responses to modifications in soil chemical properties brought about by gypsum application. The aim of this study was to evaluate the effect of gypsum application rates on the chemical properties of a Latossolo Bruno (Clayey Oxisol), as well as on the nutrition and yield of a maize-barley succession under no-till. The experiment was set up in November 2009 in Guarapuava, Parana, Brazil, applying gypsum rates of 0.0, 1.5, 3.0, 4.5, and 6.0 Mg ha-1 to the soil surface upon sowing maize, with crop succession of barley. Gypsum application decreased the levels of Al3+ and Mg2+ in the 0.0-0.1 m layer and increased soil pH in the layers from 0.2-0.6 m depth. Gypsum application has increased the levels of Ca2+ in all soil layers up to 0.6 m, and the levels of S-SO4(2-) up to 0.8 m. In both crops, the leaf concentrations of Ca and S were increased while Mg concentrations have decreased as a function of gypsum rates. There was also an effect of gypsum rates on grain yield, with a quadratic response of maize and a linear increase for barley. Yield increases were up to 11 and 12 % in relation to control for the maximum technical efficiency (MTE) rates of 3.8 and 6.0 Mg ha-1 of gypsum, respectively. Gypsum application improved soil fertility in the profile, especially in the subsurface, as well as plant nutrition, increasing the yields of maize and barley.

Effect of rock powder and vinasse on two types of soils

Can vinasse accelerate the change of minerals in rock dust to obtain fertilizers, using residues from alcohol agro-industries and mining? Answering this question was the main objective of this study. Therefore, an experiment was set up in the laboratory in a completely randomized design using Polyvinyl Chloride (PVC) columns, in which the 0-50 cm layers of a clayey soil (eutroferric Red Oxisol) and sandy soil (Typic Quartzipsamment) were reproduced. We applied three different rates of basalt powder (0.0; 2.0, and 4.0 t ha-1) and one rate of vinasse (200 m�� ha-1) to the soils. The control was made by treatments with water (200 m�� ha-1) with the same rates of rock powder. Samples were first collected on the surface of each column (1, 15, 30, 45, 60, and 90 days after the application of vinasse and rock powder), and, at the end of the experiment, at the various depths and in leached water, to determine pH and the concentration of soluble Ca2+, Mg2+, and K+. There was a significant effect of the solvent and the soil on the surface layer, with higher concentrations found in the treatments with vinasse and in clayey soil, confirming the potential of vinasse to alter minerals in basalt powder. The resulting levels from the beginning to the end of the experiment suggest that sorption phenomena with neoformed mineral phases or organic acids may have occurred. It may be concluded that the use of rock powder and vinasse mixtures is a promising alternative for soil fertilization and recycling of waste from the sugarcane and mining industries.

Effects of surface application of calcium-magnesium silicate and gypsum on soil fertility and sugarcane yield

Lime application recommendations for amendment of soil acidity in sugarcane were developed with a burnt cane harvesting system in mind. Sugarcane is now harvested in most areas without burning, and lime application for amendment of soil acidity in this system in which the sugarcane crop residue remains on the ground has been carried out without a scientific basis. The aim of this study was to evaluate the changes in soil acidity and stalk and sugar yield with different rates of surface application of calcium, magnesium silicate, and gypsum in ratoon cane. The experiment was performed after the 3rd harvest of the variety SP 81-3250 in a commercial green sugarcane plantation of the S��o Luiz Sugar Mill (47º 25' 33" W; 21º 59' 46" S), located in Pirassununga, S��o Paulo, in southeast Brazil. A factorial arrangement of four Ca-Mg silicate rates (0, 850, 1700, and 3400 kg ha-1) and two gypsum rates (0 and 1700 kg ha-1) was used in the experiment. After 12 months, the experiment was harvested and technological measurements of stalk and sugar yield were made. After harvest, soil samples were taken at the depths of 0.00-0.05, 0.05-0.10, 0.10-0.20, 0.20-0.40, and 0.40-0.60 m in all plots, and the following determinations were made: soil pH in CaCl2, organic matter, P, S, K, Ca, Mg, H+Al, Al, Si, and base saturation. The results show that the application of gypsum reduced the exchangeable Al3+ content and Al saturation below 0.05 m, and increased the Ca2+ concentration in the whole profile, the Mg2+ content below 0.10 m, K+ below 0.4 m, and base saturation below 0.20 m. This contributed to the effect of surface application of silicate on amendment of soil acidity reaching deeper layers. From the results of this study, it may be concluded that the silicate rate recommended may be too low, since the greater rates used in this experiment showed greater reduction in soil acidity, higher levels of nutrients at greater depths and an increase in stalk and sugar yield.

EFFECT OF ALTERNATIVE MULTINUTRIENT SOURCES ON SOIL CHEMICAL PROPERTIES

The current high price of potassium chloride and the dependence of Brazil on imported materials to supply the domestic demand call for studies evaluating the efficiency of alternative sources of nutrients. The aim of this work was to evaluate the effect of silicate rock powder and a manganese mining by-product, and secondary materials originated from these two materials, on soil chemical properties and on brachiaria production. This greenhouse experiment was conducted in pots with 5 kg of soil (Latossolo Vermelho-Amarelo distrófico - Oxisol). The alternative nutrient sources were: verdete, verdete treated with NH4OH, phonolite, ultramafic rock, mining waste and the proportion of 75 % of these K fertilizers and 25 % lime. Mixtures containing 25 % of lime were heated at 800 ºC for 1 h. These sources were applied at rates of 0, 150, 300, 450 and 600 kg ha-1 K2O, and incubated for 45 days. The mixtures of heated silicate rocks with lime promoted higher increases in soil pH in decreasing order: ultramafic rock>verdete>phonolite>mining waste. Applying the mining waste-lime mixture increased soil exchangeable K, and available P when ultramafic rock was incorporated. When ultramafic rock was applied, the release of Ca2+ increased significantly. Mining subproduct released the highest amount of Zn2+ and Mn2+ to the soil. The application of alternative sources of K, with variable chemical composition, altered the nutrient availability and soil chemical properties, improving mainly plant development and K plant uptake, and are important nutrient sources.

RELA����O ENTRE ATRIBUTOS F��SICOS E QU��MICOS DOS SOLOS E A PRODUTIVIDADE DE CAPIM DOURADO NA REGI��O DO JALAP��O, TO

Na regi��o do Jalap��o, no Estado do Tocantins, existem grandes ��reas cont��nuas de Neossolos Quartzar��nicos, com desenvolvimento do capim dourado (Syngonanthus nitens),esp��cie nativa utilizada na confec����o de artesanatos nessa regi��o, possuindo destacada import��ncia na economia local. O objetivo deste estudo foi verificar a rela����o entre os atributos f��sicos e qu��micos dos solos e a produtividade de capim dourado nos Campos Limpos ��midos associados ��s Veredas no Parque Estadual do Jalap��o. Foram coletadas amostras de solo e escapos de capim dourado e realizadas medi����es de declividade do terreno ao longo de caminhamento ou transe����es perpendiculares ��s linhas de drenagem das Veredas selecionadas para o estudo. Foram identificados tr��s tipos principais de solos ao longo das transe����es: Neossolo Quartzar��nico ��rtico t��pico, Neossolo Quartzar��nico hidrom��rfico t��pico e Organossolo H��plico f��brico t��pico. A produtividade de capim dourado foi analisada por meio de modelos de regress��o m��ltipla, envolvendo 26 vari��veis dos solos. Em raz��o da signific��ncia, o modelo final ficou constitu��do por seis dessas vari��veis: pH, Mg2+, Ca2+, areia fina, argila e umidade do solo. O modelo de regress��o quadr��tica m��ltipla envolvendo essas seis vari��veis contemplou R2 de 0,85 e R2 ajustado de 0,81 da rela����o avaliada, onde a umidade dos solos foi a vari��vel mais importante.

Genesis, Characterization, and Classification of Mangrove Soils in the Suba�� River Basin, Bahia, Brazil

ABSTRACT Preservation of mangroves, a very significant ecosystem from a social, economic, and environmental viewpoint, requires knowledge on soil composition, genesis, morphology, and classification. These aspects are of paramount importance to understand the dynamics of sustainability and preservation of this natural resource. In this study mangrove soils in the Suba�� river basin were described and classified and inorganic waste concentrations evaluated. Seven pedons of mangrove soil were chosen, five under fluvial influence and two under marine influence and analyzed for morphology. Samples of horizons and layers were collected for physical and chemical analyses, including heavy metals (Pb, Cd, Mn, Zn, and Fe). The moist soils were suboxidic, with Eh values below 350 mV. The pH level of the pedons under fluvial influence ranged from moderately acid to alkaline, while the pH in pedons under marine influence was around 7.0 throughout the profile. The concentration of cations in the sorting complex for all pedons, independent of fluvial or marine influence, indicated the following order: Na+>Mg2+>Ca2+>K+. Mangrove soils from the Suba�� river basin under fluvial and marine influence had different morphological, physical, and chemical characteristics. The highest Pb and Cd concentrations were found in the pedons under fluvial influence, perhaps due to their closeness to the mining company Plumbum, while the concentrations in pedon P7 were lowest, due to greater distance from the factory. For containing at least one metal above the reference levels established by the National Oceanic and Atmospheric Administration (United States Environmental Protection Agency), the pedons were classified as potentially toxic. The soils were classified as Gleissolos Tiom��rficos ��rticos (s��licos) s��dico neofluviss��lico in according to the Brazilian Soil Classification System, indicating potential toxicity and very poor drainage, except for pedon P7, which was classified in the same subgroup as the others, but different in that the metal concentrations met acceptable standards.

ATRIBUTOS QU��MICOS E F��SICOS DE SOLO CULTIVADO COM OLER��CEAS EM MICROBACIA HIDROGR��FICA, AP��S DESASTRE AMBIENTAL

RESUMO A mat��ria org��nica do solo �� uma importante fonte prim��ria de nutrientes ��s plantas e influencia a infiltra����o, reten����o de ��gua, suscetibilidade �� eros��o e agrega����o do solo. No entanto, esse processo est�� condicionado �� qualidade e quantidade da mat��ria org��nica aportada. O objetivo deste trabalho foi avaliar a influ��ncia do desastre ambiental causado pela chuva em ��reas de produ����o de oler��ceas na regi��o Serrana do Rio de Janeiro. Foram selecionadas as seguintes ��reas: A1: sem impacto (testemunha); A2: soterramento total e cultivo de aveia + ervilhaca; A3: transbordamento do rio e cultivo de milheto + girassol; A4: transbordamento do rio e grande deposi����o de areia com cultivo de aveia-preta; A5: transbordamento do rio com grande deposi����o de areia e sem cultivo; e A6: transbordamento do rio em pequena escala e sem cultivo. As propriedades ed��ficas analisadas foram: textura; densidade do solo (Ds); densidade de part��culas (Dp); di��metro m��dio ponderado (DMP) e di��metro m��dio geom��trico (DMG) de agregados est��veis em ��gua; pH(H2O), Al3+, Ca2++Mg2+, Na+, H+Al, K, P e carbono org��nico total (COT); e fra����es granulom��tricas e qu��micas da mat��ria org��nica. Os maiores valores de DMP e DMG foram observados nas ��reas A3 e A6, que seguem a mesma tend��ncia dos maiores teores de argila. Os teores de COT e suas fra����es qu��micas e f��sicas apresentaram diferen��as em rela����o �� testemunha com os menores valores verificados nas ��reas que foram submetidas ao impacto pelo transbordamento do rio e grande deposi����o de areia. As ��reas que foram impactadas pelo soterramento com predom��nio da fra����o argila apresentaram valores semelhantes ou superiores aos da testemunha. As vari��veis foram selecionadas e avaliadas por meio da an��lise de componentes principais, que evidenciou distin����o entre as ��reas estudadas, com separa����o entre elas associada �� textura do solo e densidade de part��culas.

Electrical Conductivity and Chemical Composition of Soil Solution: Comparison of Solution Samplers in Tropical Soils

ABSTRACT Soil solution samplers may have the same working principle, but they differ in relation to chemical and physical characteristics, cost and handling, and these aspects exert influence on the chemical composition of the soil solution obtained. This study was carried out to evaluate, over time, the chemical composition of solutions extracted by Suolo Acqua, with the hydrophilic membrane (HM) as a standard, using soils with contrasting characteristics, and to determine the relationship between electrical conductivity (EC) and concentration of ions and pH of soil solution samples. This study was carried out under laboratory conditions, using three soils samples with different clay and organic matter (OM) contents. Soil solution contents of F−, Cl−, NO−3, Br−, SO42−, Na+, NH4+, K+, Mg2+, Ca2+, were analyzed, as well as inorganic, organic, and total C contents, pH, and EC, in four successive sampling times. Soil solution chemical composition extracted by the Suolo Acqua sampler is similar to that collected by the HM, but the Suolo Acqua extracted more Na+ and soluble organic C than the HM solution. Solution EC, cation and anion concentrations, and soluble C levels are higher in the soil with greater clay and OM contents (Latossolo and Cambissolo in this case). Soil solution composition varied over time, with considerable changes in pH, EC, and nutrient concentrations, especially associated with soil OM. Thus, single and isolated sampling of the soil solution must be avoided, otherwise composition of the soil solution may not be correctly evaluated. Soil solution EC was regulated by pH, as well as the sum of cation and anion concentrations, and the C contents determined in the soil liquid phase.

Do Rates and Splitting of Phosphogypsum Applications Influence the Soil and Annual Crops in a No-Tillage System?

ABSTRACT Applications of phosphogypsum (PG) provide nutrients to the soil and reduce Al3+ activity, favoring soil fertility and root growth, but allow Mg2+ mobilization through the soil profile, resulting in variations in the PG rate required to achieve the optimum crop yield. This study evaluated the effect of application rates and splitting of PG on soil fertility of a Typic Hapludox, as well as the influence on annual crops under no-tillage. Using a (4 �� 3) + 1 factorial structure, the treatments consisted of four PG rates (3, 6, 9, and 12 Mg ha-1) and three split applications (P1 = 100 % in 2009; P2 = 50+50 % in 2009 and 2010; P3 = 33+33+33 % in 2009, 2010 and 2011), plus a control without PG. The soil was sampled six months after the last PG application, in stratified layers to a depth of 0.8 m. Corn, wheat and soybean were sown between November 2011 and December 2012, and leaf samples were collected for analysis when at least 50 % of the plants showed reproductive structures. The application of PG increased Ca2+ concentrations in all sampled soil layers and the soil pH between 0.2 and 0.8 m, and reduced the concentrations of Al3+ in all layers and of Mg2+ to a depth of 0.6 m, without any effect of splitting the applications. The soil Ca/Mg ratio increased linearly to a depth of 0.6 m with the rates and were found to be higher in the 0.0-0.1 m layer of the P2 and P3 treatments than without splitting (P1). Sulfur concentrations increased linearly by application rates to a depth of 0.8 m, decreasing in the order P3>P2>P1 to a depth of 0.4 m and were higher in the treatments P3 and P2 than P1 between 0.4-0.6 m, whereas no differences were observed in the 0.6-0.8 m layer. No effect was recorded for K, P and potential acidity (H+Al). The leaf Ca and S concentration increased, while Mg decreased for all crops treated with PG, and there was no effect of splitting the application. The yield response of corn to PG rates was quadratic, with the maximum technical efficiency achieved at 6.38 Mg ha-1 of PG, while wheat yield increased linearly in a growing season with a drought period. Soybean yield was not affected by the PG rate, and splitting had no effect on the yield of any of the crops. Phosphogypsum improved soil fertility in the profile, however, Mg2+ migrated downwards, regardless of application splitting. Splitting the PG application induced a higher Ca/Mg ratio in the 0.0-0.1 m layer and less S leaching, but did not affect the crop yield. The application rates had no effect on soybean yield, but were beneficial for corn and, especially, for wheat, which was affected by a drought period during growth.