Distribuição das formas de potássio no solo em decorrência da aplicação de calcário / Potassium forms distribution in soil as a result of lime application

O potássio existe no solo em diferentes formas e todas se encontram em equilíbrio químico dinâmico com o K da solução do solo, o qual determina a disponibilidade para as plantas e é influenciado pelo pH. O objetivo deste trabalho foi avaliar o efeito da elevação do pH e da aplicação de K na distribuição desse nutriente em suas diversas formas, em algumas classes de solos. O experimento foi conduzido em laboratório, utilizando-se cinco solos catarinenses. Os tratamentos consistiram de uma combinação fatorial entre doses de calcário (0, 0,25, 0,5, 1,0 e 1,5 vezes a quantidade de calcário indicada para elevar o pH até 6,0) e aplicação ou não de 1000 mg kg-1de K. A adição de K juntamente com calcário proporcionou aumentos no pH dos solos um pouco mais baixos em comparação com a aplicação somente do corretivo da acidez. O K na solução do solo foi a forma mais afetada pela adição de calcário, cujos teores diminuíram em todos os solos, independentemente da adição ou não de K. O aumento do pH também proporcionou diminuição do K extraível em quatro dos cinco solos, à exceção do Argissolo. Os teores de K não trocável foram os menos afetados pela calagem. A elevação do pH afeta a distribuição relativa do K entre as principais formas em que esse nutriente se encontra no solo e isso pode afetar sua disponibilidade às plantas.(AU)

All forms of potassium in the soil are in a dynamic equilibrium with K in the soil solution, which affects K availability to the plants and it is affected by the soil pH. The objective of this study was to evaluate the effect of the soil pH and K application on the distribution of soil K forms in five Brazilian soils. The experiment was conducted in laboratory, using five soils. Treatments consisted of a factorial combination including rates of limestone (0, 0.25, 0.5, 1.0 and 1.5 times the amount of lime indicated by the SMP method to raise soil pH to 6.0) and two rates of K (0 and 1000 mg kg-1). Addition of KCl, together with limestone, promoted lower values of soil pH relatively to limestone alone. Solution K was the most sensitive K form affected by liming rates, which decreased in all soils with increases on K rate, regardless of K addition. Exchangeable K also decreased in all soils with the increase on lime applied, except on the Argisol. The non-exchangeable K levels were the least affected by liming. Addition of lime affects the distribution of K among all K forms and this may affect the availability of K to the plants.(AU)

Sensitivity of tuberous roots crops to salinity in a protected environment / Sensibilidade de culturas de raízes tuberosas à salinidade em ambiente protegido

Soil salinity has been a limiting barrier for the production of vegetables in protected environments. Thus, the understanding of the sensitivity of species to this stress factor must be explored, seeking better growing conditions.Under the hypothesis that beet and radish crops are sensitive to variations in soil salinity, even at low levels, the objective of this work was to evaluate the development and productivity of these two species in soils with different salinities in a protected environment. The experimental design was completely randomized and treatments were formed by the soil salinity levels, obtained with the application of saline solution (NaCl in water), considering the soil electrical conductivity of 0.36 dS m-1as low salinity, of 1.05 dS m-1as moderate salinity and 2.43 dS m-1as elevated. For all variables analyzed, except for the relative chlorophyll index in beet plants, it was found that the increase in soil salinity resulted in significant development losses of beet and radish plants. Therefore, we concluded that beet and radish crops are sensitive to the variation in soil salinity, even in relatively low concentrations, making these species an unattractive choice for cultivation in systems that present this problem.(AU)

A salinidade dos solos tem sido uma barreira limitadora para a produção de hortaliças em ambientes protegidos. Assim, o entendimento quanto a sensibilidade das espécies a esse fator de estresse deve ser explorado, buscando melhores condições de cultivo. Sob a hipótese de que as culturas de beterraba e rabanete são sensíveis às variações da salinidade do solo, mesmo em níveis baixos, o objetivo deste trabalho foi avaliar o desenvolvimento e a produtividade dessas duas espécies em solos comdiferentes salinidades em ambiente protegido. O delineamento experimental foi inteiramente casualizado e os tratamentos foram formados pelos níveis de salinidade do solo, obtidos com a aplicação de solução salina (NaCl em água), considerando a condutividade elétrica do solo de 0,36 dS m-1como baixa salinidade, de 1,05 dS m-1como salinidade moderada e 2,43 dS m-1como elevada. Para todas as variáveis analisadas, com exceção do índice relativo de clorofila em plantas de beterraba, verificou-se que o aumento da salinidade do solo resultou em perdas significativas de desenvolvimento de plantas de beterraba e rabanete. Assim, concluímos que as culturas de beterraba e rabanete são sensíveis à variação da salinidade do solo, mesmo em concentrações relativamente baixas, tornando essas espécies uma escolha pouco atrativa para cultivo em sistemas que apresentam este problema.(AU)

Total organic carbon concentrations in ecosystem solutions of a remote tropical montane forest respond to global environmental change.

The response of organic carbon (C) concentrations in ecosystem solutions to environmental change affects the release of dissolved organic matter (DOM) from forests to surface and groundwaters. We determined the total organic C (TOC) concentrations (filtered <1-7 µm) and the ratios of TOC/dissolved organic nitrogen (DON) concentrations, electrical conductivity (EC), and pH in all major ecosystem solutions of a tropical montane forest from 1998 to 2013. The forest was located on the rim of the Amazon basin in Ecuador and experienced increasing numbers of days with >25°C, decreasing soil moisture, and rising nitrogen (N) deposition from the atmosphere during the study period. In rainfall, throughfall, mineral soil solutions (at the 0.15- and 0.30-m depths), and streamflow, TOC concentrations and fluxes decreased significantly from 1998 to 2013, while they increased in stemflow. TOC/DON ratios decreased significantly in rainfall, throughfall, soil solution at the 0.15-m depth, and streamflow. Based on Δ14 C values, the TOC in rainfall and mineral soil solutions was 1 year old and that of litter leachate was 10 years old. The pH in litter leachate decreased with time, that in mineral soil solutions increased, while those in the other ecosystem solutions did not change. Thus, reduced TOC solubility because of lower pH values cannot explain the negative trends in TOC concentrations in most ecosystem solutions. The increasing TOC concentrations and EC in stemflow pointed at an increased leaching of TOC and other ions from the bark. Our results suggest an accelerated degradation of DOM, particularly of young DOM, associated with the production of N-rich compounds simultaneously to changing climatic conditions and increasing N availability. Thus, environmental change increased the CO2 release to the atmosphere but reduced DOM export to surface and groundwater.

Phosphorus availability and dynamics in soil affected by long-term ruzigrass cover crop.

The use of grasses as cover crops in the off-season of cash crops under no-till has been largely adopted. However, soil phosphorus (P) uptake was previously shown to be reduced when ruzigrass is introduced in the rotation, affecting the viability and sustainability of this cropping system. The objective of this study was to assess the effect of ruzigrass on soil P availability and desorption kinetics under different P fertilizer application rates. A long-term field experiment where soybean (Glycine max) has been grown in rotation with ruzigrass (Urochloa ruziziensis) or fallow for 10 years, with the application of 0, 13, and 26 kg ha-1 of P, was evaluated for two consecutive years. Soil P desorption kinetics was assessed using diffusive equilibrium (DET) and gradient in thin films (DGT) techniques, as well as the DGT-induced fluxes in soils model (DIFS). Microbial biomass P (MBP) was assessed to verify if soil solution P (PDET) was reduced due to immobilization by microorganisms. Ruzigrass reduced MBP and PDET especially when P fertilizer was applied. The concentration of labile P (PDGT) was also lower after ruzigrass than in fallow. The soil ability to resupply P to soil solution was lower after ruzigrass regardless of P rates due to a slower desorption in response to the perturbation imposed by DGT. Growing ruzigrass as cover crop in the soybean off-season decreases soil P availability regardless of P fertilizer application rates by fundamentally reducing P mobility and P resupply from soil solid phase into soil solution.

Lime and calcium-magnesium silicate in the ionic speciation of an Oxisol

Plant residues and certain fertilizers accelerate soil acidification and increase the levels of aluminum-Al+3 in soils under no-tillage (NT). Silicates act as acidity amendments and as a source of silicon as in H4SiO4. An increase in the pH of soil solution causes the deprotonation of H4SiO4 and generates the anionic form (H3SiO4). The aim of this study was to evaluate the ionic speciation of Si, Al, Ca, Mg and K in aqueous extracts by means of a software calculation. Since 2006, a field experiment has been under way on an Oxisol under NT subjected to lime and calcium-magnesium silicate applications under four crop systems. The amendments were applied in Oct 2006 and in Oct 2011, aiming to raise base saturation to 70 %. Soil samples were collected in Oct 2013, at depths of 0-5, 5-10, 10-20, 20-40 and 40-60 cm. Both Ca and Mg formed complexes with dissolved organic carbon (DOC) whereas the same was not observed for potassium. These three basic cations were mostly in their free forms regardless of treatment, while Al was mostly complexed with DOC even at the lowest depths (40-60 cm). The highest value of free Al form was 15 %. Si was almost 100 % as H4SiO4, and its activity was similar to its concentration in solution for all crop systems and at all depths, regardless of amendment applied. The percentages of H3SiO4 and Al-H3SiO42+ were irrelevant, providing more phytoavailable H4SiO4 in soil solution.

Lime and calcium-magnesium silicate in the ionic speciation of an Oxisol

Plant residues and certain fertilizers accelerate soil acidification and increase the levels of aluminum-Al+3 in soils under no-tillage (NT). Silicates act as acidity amendments and as a source of silicon as in H4SiO4. An increase in the pH of soil solution causes the deprotonation of H4SiO4 and generates the anionic form (H3SiO4). The aim of this study was to evaluate the ionic speciation of Si, Al, Ca, Mg and K in aqueous extracts by means of a software calculation. Since 2006, a field experiment has been under way on an Oxisol under NT subjected to lime and calcium-magnesium silicate applications under four crop systems. The amendments were applied in Oct 2006 and in Oct 2011, aiming to raise base saturation to 70 %. Soil samples were collected in Oct 2013, at depths of 0-5, 5-10, 10-20, 20-40 and 40-60 cm. Both Ca and Mg formed complexes with dissolved organic carbon (DOC) whereas the same was not observed for potassium. These three basic cations were mostly in their free forms regardless of treatment, while Al was mostly complexed with DOC even at the lowest depths (40-60 cm). The highest value of free Al form was 15 %. Si was almost 100 % as H4SiO4, and its activity was similar to its concentration in solution for all crop systems and at all depths, regardless of amendment applied. The percentages of H3SiO4 and Al-H3SiO42+ were irrelevant, providing more phytoavailable H4SiO4 in soil solution.(AU)

Effects of zinc addition to a copper-contaminated vineyard soil on sorption of Zn by soil and plant physiological responses.

The occurrence of high levels of Cu in vineyard soils is often the result of intensive use of fungicides for the preventive control of foliar diseases and can cause toxicity to plants. Nowadays many grape growers in Southern Brazil have replaced Cu-based with Zn-based products. The aim of the study was to evaluate whether the increase in Zn concentration in a soil with high Cu contents can interfere with the dynamics of these elements, and if this increase in Zn may cause toxicity to maize (Zea mays L.). Soil samples were collected in two areas, one in a vineyard with more than 30 years of cultivation and high concentration of Cu and the other on a natural grassland area adjacent to the vineyard. Different doses of Cu and Zn were added to the soil, and the adsorption isotherms were built following the Langmuir's model. In a second experiment, the vineyard soil was spiked with different Zn concentrations (0, 30, 60, 90, 180, and 270mg Zn kg(-1)) in 3kg pots where maize was grown in a greenhouse for 35 days. When Cu and Zn were added together, there was a reduction in the quantities adsorbed, especially for Zn. Zn addition decreased the total plant dry matter and specific leaf mass. Furthermore, with the increase in the activity of catalase, an activation of the antioxidant system was observed. However, the system was not sufficiently effective to reverse the stress levels imposed on soil, especially in plants grown in the highest doses of Zn. At doses higher than 90Znmgkg(-1) in the Cu-contaminated vineyard soil, maize plants were no longer able to activate the protection mechanism and suffered from metal stress, resulting in suppressed dry matter yields due to impaired functioning of the photosynthetic apparatus and changes in the enzymatic activity of plants. Replacement of Cu- by Zn-based fungicides to avoid Cu toxicity has resulted in soil vineyards contaminated with these metals and damaging of plant photosynthetic apparatus and enzyme activity.

Soil water dynamics and litter production in eucalypt and native vegetation in southeastern Brazil

High productivity of eucalypt plantations is the result of advances in research that have led to gradual improvements in intensive silvicultural technology. High productivity notwithstanding, eucalypt plantations remain the focus of environmental concerns. Our study aimed to compare the soil water regime, litter fall and nutrients dynamics either in a fragment of native forest or in an adjacent stand of growing eucalypt. We took field measurements during the first three years of eucalypt plantation in a sandy soil in the southeastern region of Brazil. Soil moisture and internal drainage were higher during the early stages of growth of the eucalypt stand, as compared with native vegetation. However, one and a half years after planting, available soil water was similar in both vegetations. Higher water availability under the eucalypt stand during the first year occurs because of silvicultural operations (soil preparation and weed control) and the small size of eucalypt trees; these factors increase water infiltration and decrease transpiration. Total leaf fall, over the study period, was similar for both ecosystems; however, differences were observed in the winter and early spring of 2010. The transfer of nutrients to soil by leaf fall was similar except for N and S, which was higher in native vegetation. Nitrogen concentration in the soil solution was higher in native vegetation, but K was higher under the eucalypt stand, mainly to a depth of up to 0.2 m.(AU)

Soil water dynamics and litter production in eucalypt and native vegetation in southeastern Brazil

High productivity of eucalypt plantations is the result of advances in research that have led to gradual improvements in intensive silvicultural technology. High productivity notwithstanding, eucalypt plantations remain the focus of environmental concerns. Our study aimed to compare the soil water regime, litter fall and nutrients dynamics either in a fragment of native forest or in an adjacent stand of growing eucalypt. We took field measurements during the first three years of eucalypt plantation in a sandy soil in the southeastern region of Brazil. Soil moisture and internal drainage were higher during the early stages of growth of the eucalypt stand, as compared with native vegetation. However, one and a half years after planting, available soil water was similar in both vegetations. Higher water availability under the eucalypt stand during the first year occurs because of silvicultural operations (soil preparation and weed control) and the small size of eucalypt trees; these factors increase water infiltration and decrease transpiration. Total leaf fall, over the study period, was similar for both ecosystems; however, differences were observed in the winter and early spring of 2010. The transfer of nutrients to soil by leaf fall was similar except for N and S, which was higher in native vegetation. Nitrogen concentration in the soil solution was higher in native vegetation, but K was higher under the eucalypt stand, mainly to a depth of up to 0.2 m.

Phytoremediation of lead by jack beans on a Rhodic Hapludox amended with EDTA

A greenhouse study was conducted to evaluate the effects of ethylenediamine tetraacetic acid (EDTA) addition to soils on the lead (Pb) phytoextraction potential of jack beans (Canavalia ensiformis L.). In a pot experimentSoil samples (dystrophic Rhodic Hapludox) were treated with six Pb rates (0, 100, 200, 350, 1,200, and 2,400 mg kg-1 soil) applied as Pb(NO3)2 without and with EDTA application (0 and 0.5 g kg-1, respectively). Lead, Cl-, NO3-, NH4+, SO4(2-), H2PO4-, Zn2+, Cu2+, Fe3+, Al3+, Ca2+, Mg2+, K+ and DOC (dissolved organic carbon) concentrations obtained in a saturation soil extract (soil:water ratio of 1:0.3) were used for Pb speciation by means of the software Visual-Minteq 2.30. Soil Pb-availability was assessed with Diethylene triamine pentaacetic acid (DTPA) extraction. EDTA treated soils showed higher Pb (as PbEDTA2-), and Fe (as FeEDTA-) concentrations in soil solution leading to higher uptake of these elements by the jack bean. On the other hand, it decreased the concentration of stable complexes as Pb-DOC and Fe-DOC. EDTA also induced better nutrition to plants building up the concentration of non target metals (Ca, K, Mg, Zn, Cu, Fe and Mn) in shoots. Shoot dry matter yield remained constant even at the highest Pb rates after EDTA treatment. Jack bean can be considered as a potential Pb-phytoextractor. In addition, the DTPA solution was effective to assess Pb availability to the plants at all applied Pb rates.

Este estudo teve como objetivo avaliar, em condições de casa de vegetação, os efeitos do ácido etilenodiamino tetraacético (EDTA) no potencial fitoextrator do feijão-de-porco (Canavalia ensiformis L.). Amostras de um Latossolo Vermelho distrófico foram tratadas com seis doses de Pb (0, 100, 200, 350, 1.200 e 2.400 mg kg-1 de solo) aplicadas como Pb(NO3)2 com e sem a aplicação de EDTA (0 e 0,5 g kg-1, respectivamente) e colocadas em vasos. A concentração de Pb2+, Cl-, NO3-, NH4+, SO4(2-), H2PO4-, Zn2+, Cu2+, Fe3+, Al3+, Ca2+, Mg2+, K+ e COD (carbono orgânico dissolvido) foram determinadas no extrato de saturação (razão solo:água de 1:0,3) e utilizadas para especiação iônica através do software Visual-Minteq 2.30. A disponibilidade de Pb foi avaliada com solução extratora de ácido dietilenotriamino pentacético (DTPA). O solo tratado com EDTA apresentou maior concentração de Pb (como PbEDTA2-) e Fe (como FeEDTA-) na solução do solo levando a maior absorção destes elementos pelo feijão de porco. Por outro lado reduziu a concentração das espécies Pb-COD e Fe-COD. O EDTA também contribuiu com melhor nutrição da planta devido ao aumento da concentração de outros nutrientes (Ca, K, Mg, Zn, Cu, Fe e Mn) na parte aérea. A produção de matéria seca foi constante mesmo para as doses mais altas de Pb no solo. O feijão-de-porco possui potencial fitorremediador. O extrator DTPA foi efetivo em avaliar a disponibilidade de Pb para as plantas para todas as doses de Pb aplicadas.

Phytoremediation of lead by jack beans on a Rhodic Hapludox amended with EDTA

A greenhouse study was conducted to evaluate the effects of ethylenediamine tetraacetic acid (EDTA) addition to soils on the lead (Pb) phytoextraction potential of jack beans (Canavalia ensiformis L.). In a pot experimentSoil samples (dystrophic Rhodic Hapludox) were treated with six Pb rates (0, 100, 200, 350, 1,200, and 2,400 mg kg-1 soil) applied as Pb(NO3)2 without and with EDTA application (0 and 0.5 g kg-1, respectively). Lead, Cl-, NO3-, NH4+, SO4(2-), H2PO4-, Zn2+, Cu2+, Fe3+, Al3+, Ca2+, Mg2+, K+ and DOC (dissolved organic carbon) concentrations obtained in a saturation soil extract (soil:water ratio of 1:0.3) were used for Pb speciation by means of the software Visual-Minteq 2.30. Soil Pb-availability was assessed with Diethylene triamine pentaacetic acid (DTPA) extraction. EDTA treated soils showed higher Pb (as PbEDTA2-), and Fe (as FeEDTA-) concentrations in soil solution leading to higher uptake of these elements by the jack bean. On the other hand, it decreased the concentration of stable complexes as Pb-DOC and Fe-DOC. EDTA also induced better nutrition to plants building up the concentration of non target metals (Ca, K, Mg, Zn, Cu, Fe and Mn) in shoots. Shoot dry matter yield remained constant even at the highest Pb rates after EDTA treatment. Jack bean can be considered as a potential Pb-phytoextractor. In addition, the DTPA solution was effective to assess Pb availability to the plants at all applied Pb rates.

Este estudo teve como objetivo avaliar, em condições de casa de vegetação, os efeitos do ácido etilenodiamino tetraacético (EDTA) no potencial fitoextrator do feijão-de-porco (Canavalia ensiformis L.). Amostras de um Latossolo Vermelho distrófico foram tratadas com seis doses de Pb (0, 100, 200, 350, 1.200 e 2.400 mg kg-1 de solo) aplicadas como Pb(NO3)2 com e sem a aplicação de EDTA (0 e 0,5 g kg-1, respectivamente) e colocadas em vasos. A concentração de Pb2+, Cl-, NO3-, NH4+, SO4(2-), H2PO4-, Zn2+, Cu2+, Fe3+, Al3+, Ca2+, Mg2+, K+ e COD (carbono orgânico dissolvido) foram determinadas no extrato de saturação (razão solo:água de 1:0,3) e utilizadas para especiação iônica através do software Visual-Minteq 2.30. A disponibilidade de Pb foi avaliada com solução extratora de ácido dietilenotriamino pentacético (DTPA). O solo tratado com EDTA apresentou maior concentração de Pb (como PbEDTA2-) e Fe (como FeEDTA-) na solução do solo levando a maior absorção destes elementos pelo feijão de porco. Por outro lado reduziu a concentração das espécies Pb-COD e Fe-COD. O EDTA também contribuiu com melhor nutrição da planta devido ao aumento da concentração de outros nutrientes (Ca, K, Mg, Zn, Cu, Fe e Mn) na parte aérea. A produção de matéria seca foi constante mesmo para as doses mais altas de Pb no solo. O feijão-de-porco possui potencial fitorremediador. O extrator DTPA foi efetivo em avaliar a disponibilidade de Pb para as plantas para todas as doses de Pb aplicadas.

Growth and yield of corn irrigated with saline water

Corn (Zea mays L.) is an important crop in Brazil and is cultivated in all regions, including the semi-arid area of Brazil, where the occurrence of irrigation water with high concentration of salts is common. Evaluating the growth and yield of the maize hybrid 'AG 6690' irrigated with water of different salinity levels was the objective of this experiment. Sowing was performed in pots with 12 seeds on May 23, 2003, and seedlings were thinned to two plants per pot. Irrigation was accomplished when the mean soil matric potential of each treatment was approximately -30 kPa using water with seven different electrical conductivities (ECi), varying from 0.3 to 4.5 dS m-1, which were obtained by addition of NaCl and CaCl2 in the equivalent proportion of 1:1. The dry weights of all parts of the corn plants as well as their evapotranspiration and water use efficiency were reduced by salinity. Grain yield decreased by 21 and 20% for each unit increase of ECi and electrical conductivity of soil solution (ECs) above the respective threshold values of 1.7 and 4.3 dS m-1, respectivelly. Plants were able to maintain the leaf area index unaltered under moderate saline conditions.

O milho (Zea mays L.) é uma importante cultura no Brasil, sendo cultivado em todas as regiões, incluindo a região do semi-árido, onde é comum a ocorrência de águas com alta concentração de sais. Avaliar o crescimento e a produção do milho, híbrido 'AG 6690', irrigado com águas de diferentes níveis de salinidade foi o objetivo deste trabalho. O plantio foi realizado em vasos com 12 sementes por vaso, em 23 de maio de 2003, e realizado o desbaste deixando-se apenas duas plantas por vaso. A irrigação foi realizada sempre que o potencial mátrico médio do solo de cada tratamento aproximava-se de -30 kPa, utilizando-se águas com sete diferentes condutividades elétricas (ECi) variando entre 0,3 e 4,5 dS m-1, as quais foram alcançadas pela adição de NaCl e CaCl2 na proporção equivalente de 1:1. O peso seco de todas as partes da planta foi reduzido pela salinidade, assim como a evapotranspiração e a eficiência de uso de água. A produção reduziu por 21 e 20% para cada aumento unitário de ECi e ECs (condutividade elétrica da solução do solo) acima dos valores limiares de 1,7 e 4,3 dS m-1, respectivamente. As plantas foram capazes de manter a área foliar constante sob condições de salinidade moderada.

Growth and yield of corn irrigated with saline water

Corn (Zea mays L.) is an important crop in Brazil and is cultivated in all regions, including the semi-arid area of Brazil, where the occurrence of irrigation water with high concentration of salts is common. Evaluating the growth and yield of the maize hybrid 'AG 6690' irrigated with water of different salinity levels was the objective of this experiment. Sowing was performed in pots with 12 seeds on May 23, 2003, and seedlings were thinned to two plants per pot. Irrigation was accomplished when the mean soil matric potential of each treatment was approximately -30 kPa using water with seven different electrical conductivities (ECi), varying from 0.3 to 4.5 dS m-1, which were obtained by addition of NaCl and CaCl2 in the equivalent proportion of 1:1. The dry weights of all parts of the corn plants as well as their evapotranspiration and water use efficiency were reduced by salinity. Grain yield decreased by 21 and 20% for each unit increase of ECi and electrical conductivity of soil solution (ECs) above the respective threshold values of 1.7 and 4.3 dS m-1, respectivelly. Plants were able to maintain the leaf area index unaltered under moderate saline conditions.

O milho (Zea mays L.) é uma importante cultura no Brasil, sendo cultivado em todas as regiões, incluindo a região do semi-árido, onde é comum a ocorrência de águas com alta concentração de sais. Avaliar o crescimento e a produção do milho, híbrido 'AG 6690', irrigado com águas de diferentes níveis de salinidade foi o objetivo deste trabalho. O plantio foi realizado em vasos com 12 sementes por vaso, em 23 de maio de 2003, e realizado o desbaste deixando-se apenas duas plantas por vaso. A irrigação foi realizada sempre que o potencial mátrico médio do solo de cada tratamento aproximava-se de -30 kPa, utilizando-se águas com sete diferentes condutividades elétricas (ECi) variando entre 0,3 e 4,5 dS m-1, as quais foram alcançadas pela adição de NaCl e CaCl2 na proporção equivalente de 1:1. O peso seco de todas as partes da planta foi reduzido pela salinidade, assim como a evapotranspiração e a eficiência de uso de água. A produção reduziu por 21 e 20% para cada aumento unitário de ECi e ECs (condutividade elétrica da solução do solo) acima dos valores limiares de 1,7 e 4,3 dS m-1, respectivamente. As plantas foram capazes de manter a área foliar constante sob condições de salinidade moderada.

Emergence and growth of corn and soybean under saline stress

Emergence and seedling growth may be severely affected by salinity, mainly for sensitive crops. The objective of the present study was to verify the tolerance of corn and soybean to the irrigation water salinity (ECi) during the emergence and initial development stages. Seeds of corn, hybrid 'AG-6690', and soybean, cv. 'Conquista', were sown in pots containing material from a sandy-loam soil and irrigated with water of increasing salinity levels, from 0.3 to 5.9 dS m-1, giving nine levels of ECi obtained by the addition of an equivalent proportion of sodium and calcium chloride, except for ECi = 0.3 dS m-1 (tap water). Emergence of corn was not affected by salinity but seedling development was reduced for ECi above 1.5 dS m-1. Emergence and growth of soybean were reduced by water salinity and the crop was more tolerant during the emergence (ECi = 2.7 dS m-1) than in the initial development (ECi = 1.0 dS m-1) stage. Salinity of soil solution (ECs) was linearly correlated to ECi and affected the growth of corn and soybean for ECs higher than 3 and 2 dS m-1, respectively.

A emergência e o crescimento inicial podem ser severamente afetados pela salinidade, principalmente para culturas sensíveis. O objetivo do presente estudo foi verificar a tolerância do milho e da soja à salinidade da água de irrigação (CEi) nas fases de emergência e desenvolvimento inicial das plantas. Sementes de milho, híbrido 'AG-6690', e soja, cv. 'Conquista', foram semeadas em vasos contendo material de solo franco-arenoso e irrigadas com água de níveis crescentes de salinidade, variando de 0,3 a 5,9 dS m-1, totalizando nove níveis de CEi obtidos pela adição de cloreto de sódio e de cálcio em proporções equivalentes, exceto para CEi = 0,3 dS m-1 (água de torneira). A emergência do milho não foi afetada pela salinidade da água, mas o desenvolvimento das plantas foi reduzido para CEi acima de 1,5 dS m-1. A emergência e o crescimento da soja foram reduzidos pela salinidade, sendo mais tolerante na fase de emergência (CEi = 2,7 dS m-1) do que no desenvolvimento inicial das plantas (CEi = 1.0 dS m-1). A salinidade da solução do solo (CEs) foi linearmente correlacionada à CEi e afetou o crescimento do milho e da soja para CEs acima de 3 e 2 dS m-1, respectivamente.

Crescimento, morfologia radicular e liberação de compostos orgânicos por plântulas de soja em função da atividade de alumínio na solução do solo de campo natural

Aluminum toxicity in soils is considered one of the major limitations to crop production. However, some plants are able to tolerate high aluminum concentrations due to its complexation with root organic acids exudates. The simultaneous effect of pH ranges and aluminum concentration in soil solution on soybean seedlings root development was studied in a Rhodic Paleudult soil solution under natural grasses vegetation. Soybean seedlings were grown in growth chamber for three days in aerated test tubes containing 40ml soil solution (4.2µmol Al L-1), submmited to four aluminum concentrations (0.0, 0.3, 0.6 and 1.2mmol L-1) and three pH levels (4.0, 5.0 and 6.0). Root and aerial growth decreased under more acidic conditions (pH 4.0). Root growth was less affected by rhyzotoxic aluminum species at pH 5.0, even when submitted to high concentration of aluminum to the soil solution.

A toxicidade do alumínio em solos é considerada uma das maiores limitações para a produção das culturas. No entanto, algumas plantas são capazes de tolerar altas concentrações de alumínio por sua complexação com ácidos orgânicos exsudados pelas raízes. No intuito de estudar os efeitos concomitantes de faixas pH e de alumínio no desenvolvimento radicular de plântulas de soja, desenvolveu-se um trabalho na solução de um Argissolo Vermelho distrófico típico de campo natural. Cultivou-se, em câmara de crescimento, plântulas pré-germinadas de soja durante três dias dentro de tubos de ensaio aerados contendo 40ml da solução do solo (4,2µmol de Al L-1), submetidos a quatro concentrações de alumínio (0,0; 0,3; 0,6 e 1,2µmol L-1) e três níveis de pH (4,0; 5,0 e 6,0). O crescimento radicular e da parte aérea da soja foi menor em condições mais ácidas (pH 4,0). Em condições de acidez intermediária (pH H2O 5,0), o crescimento radicular foi menos afetado pelas espécies rizotóxicas de alumínio, mesmo quando submetidas a elevadas concentrações de alumínio na solução do solo.

Crescimento, morfologia radicular e liberação de compostos orgânicos por plântulas de soja em função da atividade de alumínio na solução do solo de campo natural

Aluminum toxicity in soils is considered one of the major limitations to crop production. However, some plants are able to tolerate high aluminum concentrations due to its complexation with root organic acids exudates. The simultaneous effect of pH ranges and aluminum concentration in soil solution on soybean seedlings root development was studied in a Rhodic Paleudult soil solution under natural grasses vegetation. Soybean seedlings were grown in growth chamber for three days in aerated test tubes containing 40ml soil solution (4.2µmol Al L-1), submmited to four aluminum concentrations (0.0, 0.3, 0.6 and 1.2mmol L-1) and three pH levels (4.0, 5.0 and 6.0). Root and aerial growth decreased under more acidic conditions (pH 4.0). Root growth was less affected by rhyzotoxic aluminum species at pH 5.0, even when submitted to high concentration of aluminum to the soil solution.

A toxicidade do alumínio em solos é considerada uma das maiores limitações para a produção das culturas. No entanto, algumas plantas são capazes de tolerar altas concentrações de alumínio por sua complexação com ácidos orgânicos exsudados pelas raízes. No intuito de estudar os efeitos concomitantes de faixas pH e de alumínio no desenvolvimento radicular de plântulas de soja, desenvolveu-se um trabalho na solução de um Argissolo Vermelho distrófico típico de campo natural. Cultivou-se, em câmara de crescimento, plântulas pré-germinadas de soja durante três dias dentro de tubos de ensaio aerados contendo 40ml da solução do solo (4,2µmol de Al L-1), submetidos a quatro concentrações de alumínio (0,0; 0,3; 0,6 e 1,2µmol L-1) e três níveis de pH (4,0; 5,0 e 6,0). O crescimento radicular e da parte aérea da soja foi menor em condições mais ácidas (pH 4,0). Em condições de acidez intermediária (pH H2O 5,0), o crescimento radicular foi menos afetado pelas espécies rizotóxicas de alumínio, mesmo quando submetidas a elevadas concentrações de alumínio na solução do solo.

Emergence and growth of corn and soybean under saline stress

Emergence and seedling growth may be severely affected by salinity, mainly for sensitive crops. The objective of the present study was to verify the tolerance of corn and soybean to the irrigation water salinity (ECi) during the emergence and initial development stages. Seeds of corn, hybrid 'AG-6690', and soybean, cv. 'Conquista', were sown in pots containing material from a sandy-loam soil and irrigated with water of increasing salinity levels, from 0.3 to 5.9 dS m-1, giving nine levels of ECi obtained by the addition of an equivalent proportion of sodium and calcium chloride, except for ECi = 0.3 dS m-1 (tap water). Emergence of corn was not affected by salinity but seedling development was reduced for ECi above 1.5 dS m-1. Emergence and growth of soybean were reduced by water salinity and the crop was more tolerant during the emergence (ECi = 2.7 dS m-1) than in the initial development (ECi = 1.0 dS m-1) stage. Salinity of soil solution (ECs) was linearly correlated to ECi and affected the growth of corn and soybean for ECs higher than 3 and 2 dS m-1, respectively.

A emergência e o crescimento inicial podem ser severamente afetados pela salinidade, principalmente para culturas sensíveis. O objetivo do presente estudo foi verificar a tolerância do milho e da soja à salinidade da água de irrigação (CEi) nas fases de emergência e desenvolvimento inicial das plantas. Sementes de milho, híbrido 'AG-6690', e soja, cv. 'Conquista', foram semeadas em vasos contendo material de solo franco-arenoso e irrigadas com água de níveis crescentes de salinidade, variando de 0,3 a 5,9 dS m-1, totalizando nove níveis de CEi obtidos pela adição de cloreto de sódio e de cálcio em proporções equivalentes, exceto para CEi = 0,3 dS m-1 (água de torneira). A emergência do milho não foi afetada pela salinidade da água, mas o desenvolvimento das plantas foi reduzido para CEi acima de 1,5 dS m-1. A emergência e o crescimento da soja foram reduzidos pela salinidade, sendo mais tolerante na fase de emergência (CEi = 2,7 dS m-1) do que no desenvolvimento inicial das plantas (CEi = 1.0 dS m-1). A salinidade da solução do solo (CEs) foi linearmente correlacionada à CEi e afetou o crescimento do milho e da soja para CEs acima de 3 e 2 dS m-1, respectivamente.

Internal drainage and nitrate leaching in a corn-black oat-corn succession with two split nitrogen applications

Excessive nitrate leaching represents a potential groundwater contamination. This study was carried out in an experiment area located in the city of Piracicaba/SP- Brazil, on a sandy-clayey loam soil. The objective was to evaluate internal drainage and nitrate leaching at the depth of 0.80 m in a crop succession, using 15N-labeled ammonium sulfate, in two split N applications. Evaluations were based on two corn crops, the first grown during the 2003/2004 cropping season, and the second in the 2004/2005 season, and on a black oat crop grown during the off-season. Treatments consisted of a single 120 kg N ha-1 rate, in the form of labeled (15N) ammonium sulfate, and two split N applications at 30-90 and 60-60 kg N ha-1. The fertilizer was applied in previously-defined subplots, in the first corn cultivation only (2003/04 cropping season). Evaluations included: soil physical and water content characterization; water flux density in the soil, and nitrate leaching at a 0.80 m depth; nitrogen in the soil solution derived from the fertilizer and 15N recovery by the soil solution at the end of the corn and black oat crop cycles. Loss by leaching in the 1st corn cultivation was approximately 96 and 68 kg ha-1 nitrate, for treatments with 60 kg ha-1 and 30 kg N ha-1 applied at seeding, respectively, of which only 3 and 1 kg ha-1 were from the nitrogen fertilizer.

A lixiviação excessiva de nitrato pode ocasionar a contaminação de corpos d'água. O presente trabalho foi desenvolvido em área experimental no município de Piracicaba/SP - Brasil, em um solo de textura areno-argilosa. O experimento teve como objetivo avaliar a drenagem interna e a lixiviação de nitrato à profundidade de 0,80 m com o tempo em uma sucessão de culturas, utilizando-se sulfato de amônio marcado com 15N, com dois parcelamentos de N. As avaliações foram feitas em dois cultivos de milho, o primeiro no ano agrícola 2003/2004, o segundo em 2004/2005, e um de aveia-preta na entressafra. Os tratamentos consistiram de uma dose única de 120 kg ha-1 de N, na forma de sulfato de amônio marcado (15N) e os dois parcelamentos de N foram 30-90 e 60-60 kg N ha-1. O adubo foi aplicado em subparcelas, previamente definidas, apenas no primeiro cultivo do milho (safra 2003/04). Foram avaliados: caracterização físico-hídrica do solo; densidade de fluxo de água no solo e lixiviação de nitrato na profundidade de 0,80 m; nitrogênio na solução do solo proveniente do fertilizante e recuperação de 15N pela solução do solo na profundidade de 0,80 m no final do ciclo das culturas de milho e aveia preta. A perda por lixiviação, a 0,80 m de profundidade, no 1º cultivo de milho, foi de aproximadamente 96 e 68 kg ha-1 de nitrato, para os tratamentos com 60 kg ha-1 e 30 kg ha-1 de N aplicado na semeadura, respectivamente, dos quais apenas 3 e 1 kg ha-1 foram provenientes do fertilizante nitrogenado.

Internal drainage and nitrate leaching in a corn-black oat-corn succession with two split nitrogen applications

Excessive nitrate leaching represents a potential groundwater contamination. This study was carried out in an experiment area located in the city of Piracicaba/SP- Brazil, on a sandy-clayey loam soil. The objective was to evaluate internal drainage and nitrate leaching at the depth of 0.80 m in a crop succession, using 15N-labeled ammonium sulfate, in two split N applications. Evaluations were based on two corn crops, the first grown during the 2003/2004 cropping season, and the second in the 2004/2005 season, and on a black oat crop grown during the off-season. Treatments consisted of a single 120 kg N ha-1 rate, in the form of labeled (15N) ammonium sulfate, and two split N applications at 30-90 and 60-60 kg N ha-1. The fertilizer was applied in previously-defined subplots, in the first corn cultivation only (2003/04 cropping season). Evaluations included: soil physical and water content characterization; water flux density in the soil, and nitrate leaching at a 0.80 m depth; nitrogen in the soil solution derived from the fertilizer and 15N recovery by the soil solution at the end of the corn and black oat crop cycles. Loss by leaching in the 1st corn cultivation was approximately 96 and 68 kg ha-1 nitrate, for treatments with 60 kg ha-1 and 30 kg N ha-1 applied at seeding, respectively, of which only 3 and 1 kg ha-1 were from the nitrogen fertilizer.

A lixiviação excessiva de nitrato pode ocasionar a contaminação de corpos d'água. O presente trabalho foi desenvolvido em área experimental no município de Piracicaba/SP - Brasil, em um solo de textura areno-argilosa. O experimento teve como objetivo avaliar a drenagem interna e a lixiviação de nitrato à profundidade de 0,80 m com o tempo em uma sucessão de culturas, utilizando-se sulfato de amônio marcado com 15N, com dois parcelamentos de N. As avaliações foram feitas em dois cultivos de milho, o primeiro no ano agrícola 2003/2004, o segundo em 2004/2005, e um de aveia-preta na entressafra. Os tratamentos consistiram de uma dose única de 120 kg ha-1 de N, na forma de sulfato de amônio marcado (15N) e os dois parcelamentos de N foram 30-90 e 60-60 kg N ha-1. O adubo foi aplicado em subparcelas, previamente definidas, apenas no primeiro cultivo do milho (safra 2003/04). Foram avaliados: caracterização físico-hídrica do solo; densidade de fluxo de água no solo e lixiviação de nitrato na profundidade de 0,80 m; nitrogênio na solução do solo proveniente do fertilizante e recuperação de 15N pela solução do solo na profundidade de 0,80 m no final do ciclo das culturas de milho e aveia preta. A perda por lixiviação, a 0,80 m de profundidade, no 1º cultivo de milho, foi de aproximadamente 96 e 68 kg ha-1 de nitrato, para os tratamentos com 60 kg ha-1 e 30 kg ha-1 de N aplicado na semeadura, respectivamente, dos quais apenas 3 e 1 kg ha-1 foram provenientes do fertilizante nitrogenado.

Cation exchange capacity of an oxisol amended with an effluent from domestic sewage treatment

The addition of Na-rich anthropogenic residues to tropical soils has stimulated the scientific community to study the role of sodium in both the soil solution and the exchange complex. In this study, several different methods were used to calculate the concentration of exchangeable and soluble cations and this data was then used to establish correlations between the level of these cations and both the accumulation of various elements and the dry weight of maize grown in a greenhouse under different conditions. In the closed environments of the pots, the most suitable method for calculating the effective cation exchange capacity (ECEC) was the cation exchange capacity calculated by cations removed with barium chloride solution (CEC S). Then again, the actual cation exchange capacity (CEC A) should be measured by using Mg adsorption to prevent ionic force from influencing electric charges. A strong positive correlation was obtained between the concentrations of Na in the 1:2 soil:water extracts and the accumulation of Na in the maize plants, indicating saline or double acid extractors are not needed when monitoring the Na concentration only.

A disposição de resíduos antropogênicos ricos em sódio nos solos tropicais tem despertado o interesse da comunidade científica em estudar a participação deste elemento no complexo de troca, bem como na solução no solo. Objetivou-se neste trabalho estabelecer correlações entre as concentrações de cátions trocáveis e de cátions solúveis, obtidos por diferentes métodos, com o acúmulo de elementos e com a massa seca no milho. O experimento foi conduzido em casa de vegetação, sob diferentes condições. Para experimentos em ambiente fechado (vasos), o método mais indicado para o cálculo da capacidade de troca catiônica efetiva (CTCe) é a capacidade de troca catiônica calculada a partir dos cátions removidos com solução de cloreto de bário. Ainda, a capacidade de troca catiônica atual deve ser medida ao pH do solo pela adsorção de Mg, para evitar a influência da força iônica nas cargas elétricas. Obteve-se alta correlação positiva entre a concentração de Na no extrato aquoso 1:2 e o acúmulo deste elemento nas plantas, indicando que quando somente o monitoramento do Na for necessário, pode-se desprezar o uso dos extratores salino ou duplo ácido.