ISHS Acta Horticulturae 481: International Symposium on Growing Media and Hydroponics
RELATIVE BREAKDOWN OF PEAT AND NON-PEAT GROWING MEDIA |
| Authors: | M. Prasad, J. O'Shea |
| Keywords: | H5 (Irish) peat, H2 (Swedish) peat, H2 (Finnish) peat, H3 (Baltic) peat, H4 (German) peat, wood fibre, air space, steaming, FTIR, Lignin, Cellulose |
| Abstract:
Incubation techniques were used to study the breakdown of peat and non-peat materials. Stability of the growing media is important, particularly where the crops are grown over a long term e.g. large ornamental plants in pots and for closed systems e.g. roses. If the growing medium is not stable it can result in anoxic conditions for the roots leading to poor growth. The peats studied were of varying degrees of decomposition from bogs in Ireland, Finland, Germany, Baltic States and Sweden. Non-peat material studied was woodfibre from France and Germany. Particle sizes of the peat had a major effect on the breakdown, with fine peat breaking down more than coarse peat. The degree of volume loss varied from 47% for H2 (Finnish) peat to 5% for coarse H5 (Irish) peat. Airspace decreased from 21% to as low as 3.5% over the 15 month incubation period for fine textured H2 Peat. Reduction in air space was related to volume reduction. In another trial, peat from bogs in Baltic states, Sweden, Ireland and Germany of two sizes (0–3mm and 5–10mm) were compared, and the loss in volume after nearly 2 years incubation was in the order of 13–20% for H4 and H5 peats and 29–40% for H2 and H3 peats. The degree of breakdown was inversely related to decomposition (von Post scale) and particle size. Woodfibres showed an even greater volume loss of the order of 50%. Steaming of H2 or H5 peats did not appear to have a significant effect on break down, as evidenced by changes in particle size. FTIR (Fourier Transform Infrared) analysis of peat taken before and after incubation, showed a trend towards enrichment of lignin and decrease in cellulose. | |
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