ADVANTAGES AND DISADVANTAGES OF CAT-METHOD FOR THE CHEMICAL ANALYSIS OF HORTICULTURAL SUBSTRATES AS COMPARED TO SEVERAL OTHER EXTRACTION SOLUTIONS

The advantages and disadvantages of CAT (0,0 1 M CaCl₂ + 0,002 M DTPA) method for the analysis of horticultural substrates as compared to several other extraction methods are discussed.
Acid, well buffered extraction solutions have the disadvantage of overestimation P content of substrate.
Main disadvantage of CAT as compared to water is the risk of overestimation Mn.
However water also has several disadvantages as compared to CAT. They include underestimation of exchangeable cations (e.g.
K⁺, NH₄⁺, Na⁺) and underestimating of phosphorus in substrates with high pH (e.g. compost). Particular difficult is the determination of some trace elements within the deficiency range because very often amounts near zero are extracted and therefore no distinction between deficiency and normal supply is possible.
All these disadvantages do not occur with the CAT method which contains an exchangeable cation and a chelator.
Therefore the CAT method offers an interesting alternative for the rational analysis of a number of macro- and trace elements in horticultural substrates.

International Symposium on Growing Media and Hydroponics

D. Alt

https://doi.org/10.17660/ActaHortic.2001.548.81