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Purpose Silicon (Si) can reduce abiotic stresses in plants and increase crop yield in semiarid climates. We aimed to assess the effect of an amorphous silica-based fertilizer (ASF) applied to soil on the yield, mineral nutrition, and health of an onion crop grown in northeast Brazil. Methods The ASF was applied at the rates of 0, 75, 125, 175, and 225 kg ha− 1. Yield and quality of bulbs as well as leaf concentrations of Si and nutrients were evaluated. Stress amelioration was assessed through Normalized Difference Vegetation Index (NDVI). Results ASF increased the yield of onions and enhanced the concentration of Si, N, P, K, Ca, Mg, B, Mn, Zn, and Cu in leaves. There was no ASF effect on bulb quality. NDVI indicated that applying 225 kg ha− 1 ASF to soil promoted healthier onion plants and the highest yield. Conclusions Silicon increased the yield of onions due to improved plant nutrition and stress amelioration.

Purpose: Silicon (Si) acts to reduce biotic and abiotic stresses in plants. Herein, we aimed to assess the impact of an amorphous silica-based fertilizer (ASF) applied to soil on the yield, mineral nutrition, chlorophyll fluorescence, and postharvest quality of two cultivars of table grapes grown in a semiarid climate. Methods: The cultivars Arra 15 and BRS Vitoria were submitted to the treatments control, 175 or 350 kg ha-1 ASF. Leaf and fruit samples were collected and analyzed for Si, nutrients, and postharvest quality characteristics. Photosynthetic efficiency was assessed by measuring chlorophyll a fluorescence . Results: Both cultivars showed significant responses to Si with the ASF rates of 175 and 350 kg ha-1. The characteristics improved through ASF application compared to the control were: fruit production (6 - 22 %), bunch weight (11 %), number of berries (20 - 34 %), berry crunchiness (20 %), the content of total soluble solids (13 – 20 %), the titratable acidity (13 %), the accumulation of macro and micronutrients (12 – 45 %) and the photosynthetic efficiency (5 – 33 %). Conclusions: Soil-applied Si increases the yield and quality of grapes by improving the plant response to abiotic stresses, being such effects more significant in the dry season.

Uma caracteristica inerente aos solos e a heterogeneidade, todavia, cultivos, sobretudo os mecanizados, como o de cana-de-acucar, tendem a ocasionar alteracoes que aumentam ainda mais a variabilidade nos atributos fisicos do solo. Dessa forma, o objetivo desse trabalho foi avaliar a variabilidade espacial da resistencia a penetracao em solo sob cultivo de cana-de-acucar na microrregiao do Litoral Norte paraibano. O estudo foi realizado em areas de producao de cana-de-acucar pertencentes a Usina Miriri e Bioenergia S/A. Duas areas localizam-se na Fazenda Santa Emilia II, municipio de Rio Tinto e a terceira faz parte da Fazenda Maria da Luz I, situada entre os municipios de Capim, Santa Rita e Sape, estado da Paraiba. Na ordem de solo foram selecionadas tres areas com diferentes condicoes de uso: I. Colheita manual–segundo corte (CMA); II. Colheita mecanizada – segundo corte (CME) e III. Colheita manual e mecanizada (CMM). Em cada area de estudo foram coletadas amostras georreferenciadas nas linhas e entrelinhas de plantio, seguindo malha amostral regular de 20 x 20 m.As amostras foram analisadas no Laboratorio de Fisica do Solo, do Departamento de Solo e Engenharia Rural (DSER), do Centro de Ciencias Agrarias (CCA) da Universidade Federal da Paraiba (UFPB). Para analise dos dados foi utilizada a estatistica descritiva e a geoestatistica.A media nao foi suficiente para representar a distribuicao espacial das areas analisadas; a malha de amostragem foi adequada, dentro das limitacoes do estudo, pois permitiu captar a dependencia espacial em praticamente todas as condicoes estudadas.A area de CMA apresentou os maiores valores de resistencia a penetracao (RP) dentre as tres areas.As areas de CME e CMM seguiram padrao similar, apresentando baixa RP nas camadas mais superficiais e com valores crescentes nas profundidades maiores.Diferente da CMA, a CME e CMM obtiveram valores medios de RP maiores na entrelinha de plantio, o que pode ser explicado por ser a parte que mais sofre os efeitos da compactacao impostas pelo intensivo trafego de maquinas.

Food production in areas contaminated by industrial wastes poses a serious risk to farmers and consumers. Here, we evaluate Cd, Cr, Ni, and Pb concentrations in the soils and the edible parts of lettuce, chives, tomatoes, pepper, and cassava plants grown by small farmers in areas contaminated by slag from an abandoned steel plant in Havana, Cuba. The total, environmentally available, and bioavailable concentrations of metals in the soils and the metals bioconcentration factor in the plants were determined. The risks to human health from food and soil ingestion were estimated. The total and environmentally available concentrations of Cd, Cr, and Pb were above values considered safe by international standards, with likely adverse effect on human health. Cadmium was the most bioavailable metal, reflected in the highest accumulation in the crops' edible parts. Even with negligible DTPA-available Cr concentrations in soils, the Cr concentrations in edible parts of the crops exceeded regulatory levels, suggesting that rhizosphere mechanisms may increase Cr availability. The consumption of vegetables represented 70% of the daily intake dose for Cr, Cd, and Ni, while accidental ingestion of contaminated soil is the predominant human exposure route for Pb. Our results demonstrated the health risks associated with cultivating and consuming vegetables grown on metal contaminated soils in Havana and can assist public policies capable of guaranteeing the sustainability of urban agriculture and food security.

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. RESUMO: 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.