Location: Application Technology Research Unit
Title: Cation exchange capacity of pine bark and peat substrates Authors
Submitted to: HortTechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 21, 2014
Publication Date: N/A
Interpretive Summary: Cation exchange capacity (CEC) is an important soil and substrate chemical property. It describes a substrate's ability to retain cation nutrients. Higher CEC values for a substrate generally result in greater amounts of nutrients retained in the substrate and available for plant uptake, and greater buffering against change in pH over time. The objective of this research was to determine which management factors affect CEC of pine bark substrates, the most common substrate type used in nursery crop production in the eastern U.S. We determined the variability of CEC in different sources of pine bark, as well as the influence of particle size, substrate pH, and peat amendment on pine bark CEC. We determined that particle size of the pine bark had the greatest effect on CEC. Substrate pH and peatmoss amendment had little or no effect on CEC. Nursery producers should choose a bark source with the greatest percentage of fine particles to maximize CEC.
Technical Abstract: Cation exchange capacity (CEC) describes the maximum quantity of cations a soil or substrate can hold while being exchangeable with the soil solution. While CEC has been studied for peat-based substrates, relatively little work has documented factors that affect CEC of pine bark substrates. The objective of this research was to determine the variability of CEC in different sources of pine bark and determine the influence of particle size, substrate pH, and peat amendment on pine bark CEC. Four sources of nursery-grade pine bark and sphagnum peatmoss were collected and separated in to several particle size classes and measured for CEC. Pine bark was also amended with varying rates of elemental sulfur (S) and dolomitic limestone to generate varying levels of substrate pH. The CEC varied with bark source. Part of this variation is attributed to differences in particle size of the bark sources. Pine bark and peatmoss CEC increased with decreasing particle size, although the change in CEC from coarse to fine particles was greater with pine bark than peatmoss. Substrate pH from 4.02 to 6.37 had no effect on pine bark CEC. The pine bark source with the highest CEC had similar CEC to sphagnum peat. Amending this source of pine bark with sphagnum peat had no effect on composite CEC.