ISHS Acta Horticulturae 511: XXV International Horticultural Congress, Part 1: Culture Techniques with Special Emphasis on Environmental Implications - Nutrient Management
CHARACTERIZATION OF PHYTOAVAILABLE HEAVY METAL CONTENTS IN COMPOST-PEAT SUBSTRATES - METHODS AND TOXICITY LEVELS |
| Authors: | M.K. Schenk, A.S. Bucher |
| Keywords: | Petunia x hybrida, Aqua regia extraction, CaCl-DTPA extraction, CaCl2 extraction, Cd, compost-peat substrates, Cu, H2O extraction, NH4OAc extraction, toxicity levels, Zn |
| Abstract:
Petunias were grown in mixtures of 40 vol% compost and 60 vol% white peat. The pH levels were 4, 5, 6, and 7. The compost contained different levels of heavy metals which were added to the raw material before composting. Extractable Cd, Cu and Zn contents were determined by extraction of fresh and dried substrates with H2O, 1 M NH4NO3, 0.1 M CaCl2, 1 M NH4OAc, CaCl2-DTPA (0.01 M and 0.002 M) and aqua regia. For Zn the result of CaCl2-extraction of dried substrate reflected the phytoavailability quite well. The best prediction of plant Cu content was obtained by the extraction of fresh substrates with CaCl2-DTPA. Plant Cd content could be described by the amount of Cd extracted with aqua regia from compost-peat substrates. Yield reduction was only observed with extremely high heavy metal levels whereas induced chlorosis appeared even at lower levels. Thus, the occurrence of chlorosis was chosen as toxicity parameter. Petunia leaves became chlorotic at mg kg-1 plant d.m.: 160 Zn, 12.3 Cu and 3 Cd, which was related to toxicity levels in the compost-peat substrate in mg 1–1: 6 Zn (CaCl2 extract) and 3 Cu (CaCl2-DTPA extract). For Cd two toxicity levels in the substrate were determined: 0.26 and 0.67 mg 1–1 substrate at pH 4 and pH 5 to 7, respectively. | |
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