Application of high Cu compost to Swiss chard and basil.

A greenhouse container experiment was conducted to evaluate the effect of high Cu compost on basil and Swiss chard productivity, and the accumulation of As, Ca, Fe, Hg, K, Mg, Na, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, S and Se in growth medium and plant tissue. The Cu content of the compost was over 1200 mg/kg, much higher than Canadian standards for type B compost quality. The treatments consisted of control soil (0% compost), and 20, 40 and 60% (by volume) of high Cu compost added to soil. All compost application treatments (20, 40 and 60%) resulted in increased dry matter yields in Swiss chard and basil. Addition of high Cu compost influenced basil plant development. Plants from the 20 and 40% treatments had higher numbers of buds and flowers. There were no differences between the control and 60% compost treatments with respect to flower initiation. Addition of 20, 40 and 60% compost to the soil resulted in increased EXCH fractions of Cu, but not of Mn and Zn. Compost additions resulted in increase in the HNO(3) extractable, CARB, FeMnOX, and in OM fractions of Cu, Mn and Zn in soils. Compost application increased soil pH and EC, soil HNO(3) extractable Ca, K, Mg, P, Na, B and Pb, but did not alter soil HNO(3) extractable Cd, Co, Cr, Mo, Ni, Se. Increased rates of compost application decreased tissue Ca in basil, tissue Na in both plants, increased tissue K, Mg in both plants, but, did not alter tissue P, Co, Cr, Mo, Ni of either plants, and B in basil. Tissue As, Hg, Pb, and Se from all treatments were under the detection limits of VGA-AAS (for As, Hg, Se) and ICP (for Pb). Compost additions altered basil oil chemical composition. Copper in the essential oil of basil was below 0.25 mg/l. In conclusion, the addition of high rates of relatively immature high Cu compost may not always increase Cu concentration in plants and in plant oils.