Release of Copper, Zinc, and Manganese from Rock Powder with Organic Materials Applied to Soils

Abstract

An incubation experiment was conducted using a sandy (Fluvic Cambisol) and a silty (Endostagnic Cambisol) soil to determine the release of copper (Cu), zinc (Zn), and manganese (Mn) from a sulfide-rich rock powder (grain size <0.5 mm), applied either alone or mixed with organic materials. Finely ground legume straw, wheat straw, and cow dung from an organic farm were used as organic materials. Rock powder and organic materials were mixed thoroughly with soils, moistened to field capacity, and incubated for 42 days. Soil samples were collected at weekly intervals for analysis. The solubility of Cu in soils increased over time with the addition of rock powder but decreased significantly if soils were mixed with organic materials. Treatments with organic materials alone show a lower release than the combination treatments with rock powder. These trends were similar for both soils. Although the solubility of Mn was very high in the sandy soil, it was not significantly affected either by the time of incubation or by the treatments applied. Zinc solubility was greater in organic material treatments than in the combined treatments in either soil. There were significant changes in pH with time as pH decreased in rock powder treatments. This study shows that the rock powder used here could be a potential source of soluble Cu, when used in combination with organic manure, though for Zn and Mn results are not conclusive.

Keywords:

• Chalcopyrite
• cow dung
• legume straw
• micronutrients
• solubility
• sphalerite
• wheat straw

Acknowledgments

Financial support for this study was provided by the Ecological Farming Project (No. 151265) funded by the Norwegian Research Council (NFR). M. Chaudhary is thankful to the Student Education Loan Fund for its financial assistance during her stay in Norway. We appreciate worthy suggestions from Susanne Eich-Greatorex and Hilary Mobbs during writing of this manuscript. Solfrid Lohne and Irene Eriksen Dahl are kindly acknowledged for technical support.