ISHS Acta Horticulturae 648: South Pacific Soilless Culture Conference - SPSCC
STABILITY OF PEAT ALTERNATIVES AND USE OF MODERATELY DECOMPOSED PEAT AS A STRUCTURE BUILDER IN GROWING MEDIA |
| Authors: | M. Prasad, M.J. Maher |
| Keywords: | Substrate, shrinkage, breakdown, lignin, FT-IR, coir, Hortifibre, Pietal, Toresa, lime rate, H5 peat |
| DOI: | 10.17660/ActaHortic.2004.648.17 |
| Abstract:
Breakdown of the physical structure of a growing medium can have a detrimental effect on long term crops such as container nursery stock. In this situation, the physical stability of the growing medium becomes important in maintaining favourable growing conditions. Some materials which have been suggested as substitutes for peat can undergo a large and rapid loss of structure. In this experiment four possible peat replacers or extenders, three woodfibres and composted coconut fibre (coir), were assessed for breakdown over a 21 month period. Pots filled with the materials or with a 50:50 mix with a H5 peat were placed in a ebb and flood bench in a glasshouse. Breakdown was assessed by measuring shrinkage of the medium. Two rates of lime were included. The materials were analysed for lignin content and by Fourier Transform Infrared (FT-IR) spectroscopic analysis at the start and end of the experiment. The results showed that the woodfibres generally break down rapidly over time in relation to H5 peat. There were differences in the extent of break down between the woodfibres.Composted coir was found to be relatively stable. The addition of H5 peat to all the non-peat materials led to a reduction in the rate of break down. The addition of lime accelerated break down. Breakdown of the materials was strongly negatively related to the initial lignin content and to the FT-IR peak ratio 1600/1056 cm-1 (lignin to cellulose). The change in the ratio 1600/1056 cm-1 and 1380/2900 cm-1 over time were strongly correlated with break down. Other initial FT-IR peak ratios, 1600/2900 cm-1, 1380/2900 cm-1 and 1485/1056 cm-1 were also correlated with breakdown. | |
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