Cadmium, silicon and nutrient accumulation by maize plants grown on a contaminated soil amended with a diatomaceous Earth fertilizer / Acúmulo de cádmio, silício e nutrientes por plantas de milho cultivadas em solo contaminado e adubado com fertilizante terra diatomáceas

Given that cadmium (Cd) poses high persistence in the environment and toxicity to humans, strategies to either decrease or avoid Cd entry in the trophic chain are fundamental to secure food safety. Here we assessed the effects of applying rates of Si as a diatomaceous Earth-based fertilizer on the amelioration of Cd toxicity towards maize plants grown on soil with or without pH correction. Besides determining Si and Cd concentrations, we also evaluated plant accumulation of nutrients (N, P, K, Ca, Mg, Fe, Mn, Cu, and Zn) as a function of Si doses applied to the soil. Results showed that both the Si application and the liming had a positive effect on biomass and nutrient uptake, but the Si effect on plants performance took place irrespectively to the soil pH. Silicon ameliorated Cd phytotoxicity in both limed and unlimed soils by decreasing Cd concentration in shoots and improving biomass yield and plant nutrition. Silicon alleviation of Cd-inhibitory effects on plants was more effective in the unlimed soil owing to the higher Cd availability in acidic soils. Also, taking into account the reduced transfer of Cd to shoots driven by Si, lower Cd accumulation in maize grains is likely, with implications to food safety. So, further studies on field conditions are warranted.(AU)

Considerando que o cádmio (Cd) apresenta alta persistência no ambiente e toxicidade aos seres humanos, estratégias para diminuir ou evitar a entrada de Cd na cadeia trófica são fundamentais para garantir a segurança alimentar. Neste contexto, avaliamos os efeitos de silício (Si) aplicado como fertilizante a base de terra diatomácea na amenização da toxicidade do Cd em milho cultivado em solo contaminado, com e sem correção de pH. Além de determinar as concentrações de Si e Cd, o acúmulo de nutrientes nas plantas (N, P, K, Ca, Mg, Fe, Mn, Cu e Zn) em função das doses de Si aplicadas ao solo foi avaliado. Os resultados mostraram que tanto a calagem quanto o Si tiveram efeitos positivos na biomassa e na absorção de nutrientes, mas o efeito do Si no desenvolvimento das plantas foi independente da reação do solo. O Si reduziu a fitotoxidade por Cd em ambos os solos, corrigidos e não corrigidos, diminuindo a concentração de Cd na parte aérea. A amenização da toxicidade de Cd foi mais efetiva em solos sem correção, devido à maior disponibilidade de Cd em solos ácidos. Os benefícios da aplicação de Si sobre a produção de biomassa, composição mineral e fitotoxidade do Cd foram observados em plantas cultivadas em solos com e sem correção. Considerando a transferência reduzida de Cd para a parte aérea promovida pelo Si, é provável que ocorra menor acúmulo de Cd nos grãos de milho, com implicações para a segurança alimentar.(AU)

Physicochemical characterization of fertilizers containing concentrated suspensions of CuO, MnCO3 and ZnO

The utilization of insoluble sources of micronutrients as concentrated suspensions (CSs) is increasing in Brazilian agriculture; however, much information regarding the physicochemical characterization of these products is required to demonstrate the absorption behavior by plant leaves. This study aimed to characterize the CSs available on the Brazilian market to support their potential use as foliar fertilizers. We selected five CSs containing Mn, five CSs containing Zn and three CSs containing Cu from five different companies. In each product, the mean particle size was evaluated by dynamic light scattering (DLS), the particle shape and size were evaluated by scanning electron microscopy (SEM), the aggregation degree was determined by the zeta potential and the heavy metal contents were determined by acid digestion followed by reading on ICP-OES. The mean hydrodynamic diameter of fertilizers containing Cu, Mn and Zn was 315 ± 55, 378 ± 184 and 435 ± 107 nm, respectively. The zeta potential varied from –20 to –30 mV, indicating potential particle aggregation and formation of higher structures. SEM images indicated great variation in the size and shape of the particles in each product. All products exhibited concentrations of toxic elements within the legislation thresholds. The average particle size of CSs currently marketable in Brazil does not allow their classification as nanomaterials (< 100 nm). Therefore, their foliar absorption is unlikely, once the particle size is higher than the exclusion limit observed for stomata and cuticle pathways, as well as the nutrient content as ions is low according to the solubility constant.

Physicochemical characterization of fertilizers containing concentrated suspensions of CuO, MnCO3 and ZnO

The utilization of insoluble sources of micronutrients as concentrated suspensions (CSs) is increasing in Brazilian agriculture; however, much information regarding the physicochemical characterization of these products is required to demonstrate the absorption behavior by plant leaves. This study aimed to characterize the CSs available on the Brazilian market to support their potential use as foliar fertilizers. We selected five CSs containing Mn, five CSs containing Zn and three CSs containing Cu from five different companies. In each product, the mean particle size was evaluated by dynamic light scattering (DLS), the particle shape and size were evaluated by scanning electron microscopy (SEM), the aggregation degree was determined by the zeta potential and the heavy metal contents were determined by acid digestion followed by reading on ICP-OES. The mean hydrodynamic diameter of fertilizers containing Cu, Mn and Zn was 315 ± 55, 378 ± 184 and 435 ± 107 nm, respectively. The zeta potential varied from –20 to –30 mV, indicating potential particle aggregation and formation of higher structures. SEM images indicated great variation in the size and shape of the particles in each product. All products exhibited concentrations of toxic elements within the legislation thresholds. The average particle size of CSs currently marketable in Brazil does not allow their classification as nanomaterials (< 100 nm). Therefore, their foliar absorption is unlikely, once the particle size is higher than the exclusion limit observed for stomata and cuticle pathways, as well as the nutrient content as ions is low according to the solubility constant.(AU)

Selectivity of organic compounds to the egg parasitoid Telenomus remus Nixon (Hymenoptera: Plastygastridae) / Seletividade de compostos orgânicos ao parasitoide de ovos Telenomus remus Nixon (Hymenoptera: Platygastridae)

The selectivity of insecticides, bio-protective mixtures, and biofertilizers used in organic soybean production was evaluated for adults and pupae of the egg parasitoid Telenomus remus Nixon (Hymenoptera: Platygastridae) under laboratory conditions in accordance with protocols proposed by the International Organization for Biological Control (IOBC). The products sprayed (dosage/180L of water) were: 1) Baculovírus anticarsia 140x109 cpi; 2) Bacillus thuringiensis 16.8g; 3) Azadirachtin-A, azadirachtin-B, nimbina and salamina 9.6 ppm; 4) Rotenoids 4 liters; 5) Nitrogen 1.3%, phosphorus 3.0% and total organic carbon 8.0% 3 liters; 6) Sodium silicate 2% 4 liters; 7) Copper 7% + calcium 3.3% 1.8 liters; 8) Sulfur 20% + quicklime 10% 1.8 liters; 9) Chlorpyrifos 384g (positive control); 10) Distilled H2O (negative control). The results of experiments using pupae indicate that the organic compounds were classified as harmless (Class 1), except for the copper 7% + calcium 3.3% and sulfur 20% + quicklime 10%, which were classified as slightly harmful (Class 2). The contact bioassay with adults showed that all products were classified as harmless (Class 1). Only chlorpyrifos (384g) was classified as harmful (Class 4) for both stages of the parasitoid. However, the use of this product (chlorpyrifos) is not permitted in organic farming, and even in conventional farming is recommended, where feasible, replacement of the product with one compatible with the preservation of T. remus in nature. Thus, the products tested and used in organic soybean production were considered compatible with the parasitoid eggs of T. remus.(AU)

A seletividade de diferentes inseticidas, caldas fitoprotetoras e biofertilizantes utilizados na produção de soja orgânica foi avaliada sobre adultos e pupas do parasitoide de ovos Telenomus remus Nixon (Hymenoptera: Platygastridae) em condições de laboratório, de acordo com protocolos propostos pela Organização Internacional para o Controle Biológico (IOBC). Os produtos (dose/180 L de água) foram: 1) Baculovírus anticarsia 140x109 cpi; 2) Bacillus thuringiensis 16,8g; 3) Azadirachtin-A, azadirachtin-B, nimbina e salamina 9,6ppm; 4) Rotenoides 4% 4 litros; 5) Nitrogênio 1,3%, fósforo 3,0% e carbono orgânico total 8,0% 3 litros; 6) Silicato de Sódio 2% 4 litros; 7) Cobre 7% + Cálcio 3,3% 1,8 litros; 8) Enxofre 20% + cal virgem 10% 1,8 litros; 9) Clorpirifós 384g (controle positivo); 10) Água destilada (controle negativo). O resultado dos experimentos para a fase de pupa indicaram que os compostos orgânicos foram classificados como inócuos (classe 1), exceto para as misturas cobre 7% + cálcio 3,3% e enxofre 20% + cal virgem 10%, que foram classificados como levemente nocivos (classe 2). O teste de contato com os adultos mostrou que todos os produtos foram classificados como inócuos (classe 1). Somente clorpirifós foi classificado como nocivo (classe 4) para ambas as fases de desenvolvimento do parasitoide. Entretanto, a utilização deste produto (clorpirifós) não é permitida em cultivos orgânicos, e mesmo na agricultura convencional recomenda-se, quando viável, a substituição desse produto por outro compatível com a preservação de T. remus na natureza. Sendo assim, os produtos testados e utilizados na produção orgânica de soja foram considerados compatíveis com o parasitoide de ovos T. remus.(AU)

Selectivity of organic compounds to the egg parasitoid Telenomus remus Nixon (Hymenoptera: Plastygastridae) / Seletividade de compostos orgânicos ao parasitoide de ovos Telenomus remus Nixon (Hymenoptera: Platygastridae)

The selectivity of insecticides, bio-protective mixtures, and biofertilizers used in organic soybean production was evaluated for adults and pupae of the egg parasitoid Telenomus remus Nixon (Hymenoptera: Platygastridae) under laboratory conditions in accordance with protocols proposed by the International Organization for Biological Control (IOBC). The products sprayed (dosage/180L of water) were: 1) Baculovírus anticarsia 140x109 cpi; 2) Bacillus thuringiensis 16.8g; 3) Azadirachtin-A, azadirachtin-B, nimbina and salamina 9.6 ppm; 4) Rotenoids 4 liters; 5) Nitrogen 1.3%, phosphorus 3.0% and total organic carbon 8.0% 3 liters; 6) Sodium silicate 2% 4 liters; 7) Copper 7% + calcium 3.3% 1.8 liters; 8) Sulfur 20% + quicklime 10% 1.8 liters; 9) Chlorpyrifos 384g (positive control); 10) Distilled H2O (negative control). The results of experiments using pupae indicate that the organic compounds were classified as harmless (Class 1), except for the copper 7% + calcium 3.3% and sulfur 20% + quicklime 10%, which were classified as slightly harmful (Class 2). The contact bioassay with adults showed that all products were classified as harmless (Class 1). Only chlorpyrifos (384g) was classified as harmful (Class 4) for both stages of the parasitoid. However, the use of this product (chlorpyrifos) is not permitted in organic farming, and even in conventional farming is recommended, where feasible, replacement of the product with one compatible with the preservation of T. remus in nature. Thus, the products tested and used in organic soybean production were considered compatible with the parasitoid eggs of T. remus.

A seletividade de diferentes inseticidas, caldas fitoprotetoras e biofertilizantes utilizados na produção de soja orgânica foi avaliada sobre adultos e pupas do parasitoide de ovos Telenomus remus Nixon (Hymenoptera: Platygastridae) em condições de laboratório, de acordo com protocolos propostos pela Organização Internacional para o Controle Biológico (IOBC). Os produtos (dose/180 L de água) foram: 1) Baculovírus anticarsia 140x109 cpi; 2) Bacillus thuringiensis 16,8g; 3) Azadirachtin-A, azadirachtin-B, nimbina e salamina 9,6ppm; 4) Rotenoides 4% 4 litros; 5) Nitrogênio 1,3%, fósforo 3,0% e carbono orgânico total 8,0% 3 litros; 6) Silicato de Sódio 2% 4 litros; 7) Cobre 7% + Cálcio 3,3% 1,8 litros; 8) Enxofre 20% + cal virgem 10% 1,8 litros; 9) Clorpirifós 384g (controle positivo); 10) Água destilada (controle negativo). O resultado dos experimentos para a fase de pupa indicaram que os compostos orgânicos foram classificados como inócuos (classe 1), exceto para as misturas cobre 7% + cálcio 3,3% e enxofre 20% + cal virgem 10%, que foram classificados como levemente nocivos (classe 2). O teste de contato com os adultos mostrou que todos os produtos foram classificados como inócuos (classe 1). Somente clorpirifós foi classificado como nocivo (classe 4) para ambas as fases de desenvolvimento do parasitoide. Entretanto, a utilização deste produto (clorpirifós) não é permitida em cultivos orgânicos, e mesmo na agricultura convencional recomenda-se, quando viável, a substituição desse produto por outro compatível com a preservação de T. remus na natureza. Sendo assim, os produtos testados e utilizados na produção orgânica de soja foram considerados compatíveis com o parasitoide de ovos T. remus.