Maria Ligia de Souza Silva

Deficiências de macronutrientes no estado nutricional da mamoneira cultivar Iris

The objectives of this work were to evaluate the effect of macronutrient deficiencies on growth and on nutritional status of castor beans ( Ricinus communis L.), and to obtain the symptoms of the lack of N, P, K, Ca, Mg and S. Nutrient solutions containing all macronutrients and those from which one of these elements was omitted were the treatments used. The following determinations were made: chlorophyll (indirectly), nitrate reductase activity, NO 3 - -N, H2PO4 - -P and K + , both on soluble fractions, and by spot tests. Deficiencies of N, Ca, S and Mg were the most limiting for dry matter production, followed in decreasing order by those of K and P. The highest concentrations of macronutrients were measured in roots and lower leaf blades. Critical levels of N and Ca in the upper leaf blades and of Mg in lower petioles were respectively, 46.7, 13.8, 6.5 g kg -1 . Deficiencies affected chlorophyll meter readings. Nitrate reductase activity was correlated with chlorophyll readings. Soluble contents of N, P and K in the leaves were lower in plants deficient in the respective element. The same was found when spot tests were applied on the leaf sap.

Heavy metal toxicity in rice and soybean plants cultivated in contaminated soil

Os metais pesados podem-se acumular no solo, causando fitotoxicidade em plantas, apresentando alguns sintomas especificos. Por esta razao, este estudo avaliou os sintomas especificos, em plantas de arroz e de soja, causados por excesso de metais pesados no solo. As plantas de arroz e de soja foram cultivadas em vasos, contendo solos com diferentes quantidades de metais pesados. O delineamento experimental foi inteiramente casualizado, com quatro repeticoes, utilizando-se duas culturas e sete amostras de solos com diferentes niveis de contaminacao. As plantas de arroz e de soja exibiram diferentes respostas as elevadas concentracoes desses metais no solo. Por exemplo, altas concentracoes de Zn disponivel no solo causaram fitotoxicidade no arroz e na soja, principalmente cloroses e inibicao do crescimento das plantas. As plantas de arroz acumularam maiores teores de Cu, Mn, Pb e Zn e foram mais sensiveis as concentracoes elevadas desses elementos no solo, absorvendo-os mais facilmente do que as plantas de soja. Alem disso, altas concentracoes de Zn no solo reduziram a concentracao de Fe na parte aerea das plantas de soja e de arroz para niveis considerados deficientes.

Fracionamento de metais pesados em solo contaminado antes e após cultivo de arroz

The objective of the present work was to evaluate the distribution of Cd, Cu, Mn, Pb and Zn among the different fractions of contaminated soil, before and after rice cultivation. Seven soil samples with different degrees of contamination were studied using a randomized experimental design, with four replicates. Using an ICP-OES we analyzed the contents of heavy metals in fractions of soil, the organic matter therein, the oxides and the residual content before and after rice cultivation. The largest concentrations of Cd, Cu, Mn and Zn in the soil are found in the fractions with stable chemical bonds.

Availability of heavy metals in contaminated soil evidenced by chemical extractants

Heavy metals have been accumulating in Brazilian soils, due to natural processes, such as atmospheric deposition, or human industrial activities. For certain heavy metals, when in high concentrations in the soil, there is no specific extractant to determine the availability of these elements in the soil. The objective of the present study was to evaluate the availability of Cd, Cu, Fe, Mn, Pb and Zn for rice and soybeans, using different chemical extractants. In this study we used seven soil samples with different levels of contamination, in completely randomized experimental design with four replications. We determined the available concentrations of Cd, Cu, Fe, Mn, Pb and Zn extracted by Mehlich-1, HCl 0.1 mol L -1 , DTPA, and organic acid extractants and the contents in rice and soybeans, which extracts were analyzed by ICP-OES. It was observed that Mehlich-1, HCl 0.1 mol L -1 and DTPA extractants were effective to assess the availability of Cd, Cu, Pb and Zn for rice and soybeans. However, the same was not observed for the organic acid extractant.

Copper and zinc quantification in contaminated soil as evaluated by chemical extractants

Trace elements are potentially toxic to the environment. Their toxicity in soils relies on their type of chemical associations. Hence it is important to determine the chemical form they occur in the soils in order to assess their quantities. The objective the present work was to evaluate the possibility of using the concentrations of Cu and Zn in different soil fractions and the total concentration as predictors of their quantification by comparing the classical extractants DTPA, Mehlich-1 and HCl. Comparisons were made also with the concentrations of absorbed by rice and soybean in contaminated soil. Seven soil samples with a different degree of contamination were studied using a randomized experimental design, with four replicates. By using an ICP-OES we analyzed the concentrations of Cu and Zn in the diagnostic leafs, at the end of the cycle (LCE) and several of its content in the soil: available extracted with the DTPA, Mehlich-1 and HCl extractants, soluble+exchangeable contents, bound to organic matter, to oxides and the total content. For both, soybean and rice, the concentrations of Cu and Zn extracted from the sequential extraction was found to be correlated with the concentration in LCE. For soybean, Zn concentration extracted with DTPA was correlated with the total concentration, while Cu concentration extracted with three extractors, DTPA, Mehlich-1 and HCl, correlated with the total concentration, probably due to the high concentration of Cu and Zn in this soil. For rice, both Cu and Zn concentration as extracted by the three extracting solutions correlated with the concentration of all the fractions and with the total concentration.

Influência do nitrogênio e enxofre na produção do feijoeiro

Na fisiologia das plantas, limitacoes de nitrogenio (N) ou enxofre (S) sao manifestadas no ponto de convergencia das rotas assimilatorias, o que ocasiona acumulo ou carencia de produtos sintetizados. O objetivo do trabalho foi avaliar a influencia da interacao entre o N e S no desenvovlimento da cultura do feijoeiro. O experimento foi conduzido em casa de vegetacao, em vasos contendo 4 dm 3 de solo. O experimento foi instalado em esquema fatorial 2 x 5, sendo duas doses de N (80 e 120 mg dm -3 ) e cinco doses de S (0, 30, 60, 90 e 120 mg dm -3 ), com tres repeticoes por tratamento. Os tratamentos foram aplicados aos vasos e semeado o feijao. O experimento foi conduzido por 80 dias, ao final do ciclo as plantas foram separadas em graos e parte aerea. As amostras vegetais da parte aerea foram secas, moidas e analisadas em relacao ao teor de N e S. A produtividade de graos do feijoeiro foi influenciada pela adubacao nitrogenada e sulfatada, sendo que o mesmo nao ocorreu para a producao de materia seca da parte aerea. A absorcao de S pela cultura do feijoeiro foi diretamente influenciada pela adubacao nitrogenada. A relacao N/S na cultura do feijoeiro foi diretamente influenciada pela adicao de N e S. Os valores de N/S nao correlacionaram-se com a producao de graos ou materia seca da parte aerea.

Gesso agricola como fonte de enxofre para a cultura do morango

There are several studies on plant responses to Sulfur (S), but few are specific to the strawberry crop. The requirement for nutrients and the nutritional status of plants is a particular attribute of each species that should be taken into account when determining the plant’s nutritional demand. The objective of this study was to evaluate the application of S and phosphate (P) rates in the development and productivity of strawberry crops. An experiment was conducted in a greenhouse in pots containing 2 kg soil (Oxisol) in Guarapuava city of Paraná State. The experiment consisted of a 6 × 2 factorial outlined in a randomized block design with three replications, with six doses of S: 0, 10, 20, 30, 40 and 50 mg kg-1 in the form of gypsum, and two doses of P: 300 and 600 mg kg-1 of P2O5. The Albion variety of strawberry plants was transplanted to pots and grown for 170 days. The fruits were harvested and weighed throughout the experiment; a similar procedure was followed for the shoots at the end of the experiment. The shoots and fruits were dried, weighed, ground, and analyzed for the content of S, Ca, and P. The production of strawberry fruits was influenced by S rates, with the highest productivity obtained by using S rates of 60 and 37 mg kg-1 with the application of 300 and 600 mg kg-1 of P, respectively.