RHP pH buffer test on growing media constituents

H. Verhagen, I. Geuijen
For years, peat has been the main component of growing media. Due to its decomposition, peat has a high content of humic and fulvic acids, which buffer cations. This cation exchange capacity (CEC) not only buffers nutritional elements such as ammonium, potassium, calcium, and magnesium, but also buffers hydrogen and thus the pH of the growing medium. Nowadays, growing media consist of constituents other than peat. Among others, coir, wood fiber, bark, and green waste compost are often used in growing media. These materials differ strongly from peat in general in terms of size of the buffer and initial pH. Whereas most sphagnum moss peats do require a certain amount of liming to set the desired pH, other organic constituents can show pH levels that are considered too high for many cultures. When producing a growing medium with various components, it can be difficult to achieve the desired pH. For this reason, RHP has developed a pH buffer test. Based on titration, the pH buffer of a constituent is measured. With the results, it can be calculated which pH level is realized when combining various constituents. Also, when applied to ready-to-use growing media, the pH buffer test provides insight into the stability or instability of the pH in a culture.
Verhagen, H. and Geuijen, I. (2024). RHP pH buffer test on growing media constituents. Acta Hortic. 1389, 237-240
DOI: 10.17660/ActaHortic.2024.1389.26
growing media, constituents, pH, pH-buffer, test method

Acta Horticulturae