Copper availability as related to soil copper fractions in oxisols under liming

Abstract

The knowledge of the chemical forms of copper in soils and the relationships of these forms with soil copper availability are important for predicting the copper behavior in the soil-plant system. The present work studies the influence of liming on the available contents of copper as well as on the forms of copper fractions in six types of Oxisols. Soil samples, with and without liming, received copper at rates of 0.0, 20.0 and 40.0 mg dm-3 and remained incubated for 30 days. Then, available copper was extracted with Mehlich-1, Mehlich-3, DTPA and EDTA solutions, and analyzed by atomic absorption spectrophotometry. Additionally, soil samples were extracted in a sequential procedure to determine Cu in fractions of soil, as follows: exchangeable-Cu fraction, organic matter-Cu fraction, Mn oxide-Cu fraction, amorphous Fe oxide-Cu fraction, crystalline Fe oxide-Cu fraction, residual-Cu fraction, and the total Cu content in the soil. Soil samples to which Cu was added presented higher Cu retention in the organic matter fraction with a small percentage retained in the exchangeable-Cu fraction. Liming resulted in a decrease of Cu in the exchangeable and organic matter fractions and an increase in the Fe and Mn oxide fractions and in the residual fraction. Without liming, the organic matter fraction presented the highest contribution to Cu content found in the soil extracts obtained with all extractors, except EDTA. For treatments with liming, Cu contents in the organic matter fraction were better correlated to Cu contents in extracts obtained with DTPA and Mehlich-3.

Micronutrient Soil-Test Levels andEucalyptusFoliar Contents

“…In general, the Mehlich 1 and Mehlich 3 solutions extracted more Cu, Mn, Fe, and Zn from soils than DTPA (Table 2), as reported by other authors (Cancela et al 2001;Nascimento, Fontes, and Melicio 2003;Gonçalves et al 2006;Obrador et al 2007). Acid extractants such as Mehlich 1 and Mehlich 3 have a greater extraction power because of acid dissolution of soil micronutrient fractions such as oxides that are not extracted by DTPA (Cancela et al 2001;Nascimento 2001;Ferreira 2003;Abreu et al 2004).…”

Effect of Liming on the Plant Availability and Distribution of Zinc and Copper among Soil Fractions

“…As the pH increases, the number of negative pH-dependent charges also increases, but the negative charge density at the surface of the colloid increases, and the micronutrients available for the plant decrease. In addition, liming decreases Zn and Cu in the plant-available fractions, that is, exchangeable and organic matter (Shuman 1986;Nascimento et al 2002;Nascimento, Fontes, and Melício, 2003). Thus, information on the redistribution of applied micronutrients into different forms is important to predict the plant accumulation as well as to select appropriate chemical extraction procedures for micronutrient availability assessment.…”

Disponibilidade e fracionamento de Cd, Pb, Cu e Zn em função do pH e tempo de incubação com o solo

“…No entanto, a concentração de Cu em forma trocável foi inferior ao teor do elemento na matéria orgânica, indicando a pouca afinidade dos sítios de troca catiônica pelo elemento (ATANASSOVA & OKAZAKI, 1997;NASCIMENTO et al, 2003). Foi observado aumento de 18% da concentração de Cu na fração trocável e redução de 28, 37 e 43% na fração matéria orgânica, óxidos de ferro amorfo e cristalino entre o maior e o menor tempo de incubação.…”

“…A fitorremediação de solos contaminados por metais pesados tem atraído atenção pelo seu baixo custo e benefícios ambientais (SALT et al, 1998). Entre as técnicas mais eficientes de fitorremediação, a fitoextração consiste no uso de plantas para absorver, transportar e concentrar metais do solo para a parte aérea (NASCIMENTO & XING, 2006). O emprego de agentes quelantes, como EDTA, HEDTA e ácido cítrico, podem aumentar a mobilidade dos metais no solo e suas acumulações em plantas (CHEN et al, 2003), aumentando, portanto, a eficiência da fitoextração.…”