A STUDY OF ONIONS GROWN IN MICROPLOTS ON THREE ORGANIC SOILS EACH CONTAINING FOUR LEVELS OF COPPER

Publisher Website
Google Scholar
Abstract
To assess effects of soil Cu on the yield and nutrition of a crop, onions (Allium cepa ’Autumn Spice’) were grown in field microplots at sites A (peat), B (muck) and C (mucky peat). The surface layers (0–20 cm) of the plots contained four levels of residual fertilizer Cu up to 1200 ppm (wt/wt) at sites A and B and up to 600 ppm at site C. The highest Cu treatment at sites A and B contained about 4–6 times the Cu required for mitigating the excessive decomposition and subsidence of such organic soils. Neither the Cu treatment level nor the total soil Cu concentration influenced crop yields at sites B or C. Crop yield responded positively to the two highest Cu treatment levels at site A where the background level of soil Cu was the lowest among the three sites. The Cu concentrations in the crop at all sites were below the level considered to be phytotoxic (20 ppm). Fe and Zn contents in plants were also not depressed by higher Cu concentrations except for foliar Fe on the highest Cu treatment plots at site A. These plots were intrinsically poorer in Fe than those treated with lesser Cu. Foliar Fe:Cu and Zn:Cu ratios were also lowest, but not below adverse levels, for the highest Cu treatment levels at sites A and B, respectively. Even the highest levels of soil Cu did not reduce N supply for, or N nutrition of, the onion crop, or alter the crop concentrations or uptakes of P, K, Ca, Mg and Mn. Key words: Copper, onions, subsidence, histosol, muck, peat

This publication has 1 reference indexed in Scilit: