Retention and leaching of copper and zinc in "Tabuleiro" soils as influenced by nutrient carrier

Abstract

The "tabuleiro" soils, due to their topography and physical  properties, would be advantageous for agricultural development. However, they are sandy, highly leached and extremely infertile. Deficiencies reported include thoso of copper and zinc. Nutrient carriers which are not readily leached, but which will gradually release available forms for uptake by the crop would be most suitable. Determinations of the retention and leaching of copper and zinc, as related to carrier, were made on samples taken from 0-20 and 20-40 cm depths of Red Yellow Podzolic and Hydromorfic Podzol soils from the State of Pernambuco. The 0-20cm layer of the Blodgett soil of Western Montana was included for comparison. Both elements were readily retained by the top soils, and to a greater extent than for subsoils. The Red Yellow Podzolic soil retained more copper and zinc than Hydromorfic Podzol soil at comparable depths. The organic fractions retained much more copper and zinc than mineral fractions of the same soil. The Blodgett soil retained more copper than the corresponding depth of Brazilian soils, however zinc was retained almost equally. The sulphate forms of copper and zinc were leached less readily than resin adsorbed or chelated forms. Up to 100 percent of the copper or zinc added in these latter two forms was leached from the soil. Effects of adding peat to the soil or removing soil organic matter were variable with respect to copper or zinc retention. Results suggest that salt forms of copper and zinc may be very efficient for combatting deficiencies.