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Characterization of phytoavailable zinc in compost‐peat substrates — Comparison of methods
Author(s) -
Bucher Annette S.,
Schenk Manfred K.
Publication year - 1997
Publication title -
zeitschrift für pflanzenernährung und bodenkunde
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 0044-3263
DOI - 10.1002/jpln.19971600511
Subject(s) - compost , peat , extraction (chemistry) , chemistry , aqua regia , zinc , environmental chemistry , agronomy , chromatography , metal , ecology , organic chemistry , biology
Compost of separately collected green yard and organic household wastes may contain high amounts of Zn. Hence, substrates basing on compost can result in Zn phytotoxicity. The aim of the investigations was to identify a suitable reagent to characterize phytoavailable Zn in compost‐peat substrates. Petunia hybrids were cultivated in compost‐peat substrates with increasing Zn amounts (basic load, 400, 800, 1600 mg kg −1 d.m. aqua regia soluble). Extractable Zn was determined by extraction of fresh and dried substrates with H 2 O, 1 M NH 4 NO 3 , 0.1 M CaCl 2 , 1 M NH 4 OAc, and CaCl 2 ‐DTPA (0.01 M + 0.002 M). The Zn content of plants increased significantly with increasing Zn application and decreasing pH. The result of CaCl 2 and NH 4 OAc extraction reflected the influence of pH on Zn phytoavailability quite well and the correlation with the plant Zn content was very good. Extraction with H 2 O and NH 4 NO 3 did not give acceptable results. Extraction with CaCl 2 ‐DTPA was inconsistent for all trials and thus not suitable. The percentage of CaCl 2 ‐extractable Zn in relation to the aqua regia soluble content at the same pH varied over the trials. Thus, the phytoavailable content of the substrates is influenced by additional factors, besides Zn supply and pH. The result of CaCl 2 extraction of dried substrates resulted in the best reflection of Zn phytoavailability and was used for all further investigations, including determination of critical values of phytotoxic Zn. Plant yield was not influenced by the Zn treatments. However, Zn induced chlorosis of petunias occurred at a plant Zn content > 160 mg kg −1 d.m. and a phytoavailable Zn content in the substrate > 6 mg l −1 in CaCl 2 extract and > 2.6 mg l −1 in NH 4 OAc extract, respectively.