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United States Department of Agriculture

Agricultural Research Service

Title: Spatial Variability of Grain Cadmium and Selected Soil Characteristics in Adurum Wheat Field

Authors
item Wu, J - CORNELL UNIVERSITY
item Norvell, Wendell
item Hopkins, D - NORTH DAKOTA UNIVERSITY
item Welch, Ross

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 25, 2001
Publication Date: February 1, 2002
Citation: WU, J., NORVELL, W.A., HOPKINS, D.G., WELCH, R.M. SPATIAL VARIABILITY OF GRAIN CADMIUM AND SELECTED SOIL CHARACTERISTICS IN ADURUM WHEAT FIELD. SOIL SCIENCE SOCIETY OF AMERICA JOURNAL. 2002. v. 66. p. 268-275.

Interpretive Summary: Cadmium (Cd) is a heavy metal that is present in all soils, usually as a trace constituent. Accumulation of Cd in edible crops is undesirable because of potential damage to health. Soil salinity, especially chloride (Cl) salinity, has been identified as a factor that enhances the availability of soil Cd. This research measured the degree to which the distribution of Cd in durum wheat grain was linked to the distribution of soil characteristics including extractable Cd, pH, cation exchange capacity, organic matter, and soluble chloride, sulfate, and sodium. The field studied was located in northeastern North Dakota. A total of 124 paired samples of top soil and durum wheat (Triticum durum L.) grain were collected and analyzed. The concentration of Cd in grain (Cdg) averaged 0.182 mg kg-1, but varied over a 15-fold range. The distribution of Cdg and soil properties were strongly spatially dependent. The distribution of fCdg was more similar to a logarithmic function of soil Cl than to any othe measured property. The association of Cdg with soluble sulfate and sodium was also close. Mathematical models of spatial variation were used to create maps for all variables. These showed that elevated Cdg and soil Cl were distributed similarly. About 85% of the variations in the Cdg map were explained by variations in the map for soil Cl. Locations with well or moderately well-drained soils containing lower Cl produced grain with lower Cdg. Conversely, locations with somewhat poorly drained soils with elevated Cl produced grain with higher Cd. The results suggest that knowledge of the spatial distribution of soil characteristics, especially salinity, will aid in the development of agronomic practices to reduce Cd in durum grain.

Technical Abstract: The accumulation of Cd in edible crops is undesirable because of potential damage to health. Soil salinity, especially chloride (Cl) salinity, has been identified as a factor that enhances the availability of soil Cd. The extent & scale of spatial variability in crop Cd & related soil factors was measured in a field with variable salinity in northern North Dakota. We collected 124 paired soil (0-15cm) & durum wheat (Triticum durum L.) grain samples from within an area of about 0.5 ha. The concentration of Cd in grain (Cdg) averaged 0.182 mg kg-1, but varied over a 15-fold range. 8 soil characteristics were measured, including chelate-extractable Cd, pH, cation exchange capacity, organic carbon, & soluble Cl, sulfate, & sodium. Semivariograms showed that the spatial variations of Cdg & soil properties were strongly spatially dependent. The semivariogram for Cdg was more similar to that for the natural log of soil Cl (LnCl) than to any other measured property. A spherical model was fitted to all variograms, except for that of total soil Cd. Maps of Cdg & each soil characteristic were generated by Block Kriging. Analysis of map overlay showed that elevated Cdg & soil Cl were distributed similarly. Locations with well or moderately well-drained soils containing lower Cl produced grain with lower Cdg. Conversely, locations with somewhat poorly drained soils with elevated Cl produced grain with higher Cd. Maps of Cdg & LnCl were highly correlated, so that about 85% of the variations in the Cdg map were explained by variations in the map for soil Cl. Results suggest that knowledge of the spatial distribution of soil characteristics, especially salinity, can aid in the development of agronomic practices to reduce Cd in durum grain.

Last Modified: 11/27/2014
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