The Effect of Soil Depth and Canopy of Three Date Palms on Release of Copper from a Calcareous Soil

Copper is an essential micronutrient to plants, which it`s deficiency is common in calcareous soil. Most of the soils are calcareous in Iran, therefore farmers and gardeners may observe the deficiency of this element during the growing season. Given the importance of copper in the nutrition of date trees, especially in calcareous soils, a better understanding of the mechanism and kinetics of copper release from the soil can provide useful information about the factors affecting the bioavailability of this element. Therefore, this study was conducted to investigate the influence of depth and canopy of three palm cultivars on kinetics release of copper. For this purpose, soil samples were collected from three depths of 0-20, 20-40 and 60-40 cm and two locations (under canopy and outside the canopy) with three replications, for three cultivars of date palms; Shahani, Ghasab and Halvan. Extraction was performed in eight different time periods with ammonium bicarbonate Diethylene Triamine Penta acetic acid (AB-DTPA). Results showed that the power function, simple Elovich, and parabolic diffusion were the best fitted models for describing Cu release. The pattern of copper release was fast during the first two hour and decreased at subsequent time. The results of this study indicating the positive effect of date palm canopy on the availability and rate of copper release from calcareous soils. So that the rate of copper release related to the depth of 40-60 cm of the soils under the canopy was higher than the one in the same depth outside the canopy, which can be attributed to root exudations and pH reduction. Among the three cultivars studied in this research, Shahani cultivar had the highest amount of copper release.