|Authors: ||M.J. Maher, M. Prasad|
|Keywords: ||degree of decomposition, pH, water quality|
Peats which are more decomposed may have a greater buffering capacity and therefore be more stable with regard to pH and physical structure than younger peats.
Peats from three sources, Ireland (H5 on the von Post scale), Latvia (H2) and Lithuania (H2) in combination with three rates of dolomitic lime (2, 3 and 4 kg m-3) were studied for their effect on pH and stability of the growing medium and on the growth of Hebe pinguifolia ‘Sutherlandii’ over a period of one year.
Two experiments were conducted in ebb and flood benches: one irrigated with hard (325 mg L-1 bicarbonate) water and the second with rainwater (zero bicarbonate). With soft water, pH in the H5 peat declined gradually while it was stable in the H2 peats.
Where hard water was used, pH rose sharply in the second half of the experiment but much less in the H5 than in the H2 peats.
At the low rate of lime, shrinkage of the growing medium was similar for all three peats but higher lime rates increased shrinkage in the H2 peats.
The Lithuanian (H2) peat produced the heaviest plants at a lime rate of 2 kg m-3 but at 4 kg m-3 fresh weight was greatest in the H5 peat.
Growing medium shrinkage was significantly and positively related to the pH of the medium towards the end of the experiments.
Plant fresh weight was significantly and negatively related to growing medium shrinkage and to pH.
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