Copper Activity in Soil Solution: II. Relation to Copper Accumulation in Young Snapbeans1
- M. M. Minnich,
- M. B. McBride and
- R. L. Chaney2
Soil solution Cu2+ activity measured in soil saturation extracts was compared with Cu accumulation in young snapbeans (Phaseolus vulgaris L.). Copper was supplied through sewage sludge mixtures of varied Cu concentrations and through Cu-salt additions to the soil. Treatments were a factorial combination of four levels of Cu additions and four levels of total sludge additions. Soil and sludge pH values were limited to pH 5.0 to 5.5. Plant yield differences were minor. Data are reported showing the relationships of root, shoot, and total plant Cu contents with Cu2+ activity, with DTPA-extractable Cu, with soluble Cu, and with sludge Cu concentration. The Cu source (sludge vs. salt) produced distinctly different curves in most every case. Sludge treatments demonstrated nonlinear relationships of Cu activity vs. Cu accumulation; these were fit with exponential functions. Higher shoot Cu concentrations occurred with the Cu salt treatments. Higher root Cu levels occurred at lower Cu2+ activity values with sludge as the Cu source. This probably reflects the superior ability of the sludge to replenish or maintain the Cu supply in soil solution. Total soluble Cu was not related to plant Cu. The proportion of Cu in the sludge was closely linked with shoot Cu (r2 = 0.94); root Cu levels also reflected the proportion of Cu in the sludge, but higher sludge rates resulted in increased root Cu. Increased labile, soluble, Cu-organic complexes with increased sludge rates would explain both the observed differences between salt and sludge treatments and the positive correlation of root Cu and sludge rate. Physiological control of Cu translocation within the plant is implicit in this reasoning. Continual monitoring of soil solution ion activity or a buffering index is needed to improve predictions of plant ion uptake.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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