|Authors: ||H.E. Kresten Jensen, M. Leth, J.J. Lønsmann Iversen|
|Keywords: ||peat substitute, ammonium sulphate, urea, pig slurry, composting, water retention, volumetric water content, plant growth|
Shredded straw of Miscanthus x ogiformis Honda ‘Giganteus’ was composted with tap water as control and ammonium sulphate, urea, or pig slurry as N-source.
The C/N (w/w) was 27 with ammonium sulphate, 27 with urea, 19 with pig slurry and 96 with tap water.
Within two days of composting peak temperatures rose to 65°C for pig slurry and within three days 59°C for ammonium sulphate, 41°C for urea and 59°C for tap water.
After five months the composts were compared to unfertilized peat and fertilized peat as growth substrates for Hedera helix ‘Mein Hertz’ and Fatsia japonica. Un-rooted cuttings of Hedera and pre-rooted cuttings of Fatsia were grown in 9 cm pots according to a standard growing program using ebb and flood liquid fertilization under glass.
After 12 weeks shoot lengths of Hedera were similar in composts with Miscanthus and urea, or pig slurry and fully fertilized peat (13.5 -16.0 cm). Shoot lengths were shorter for compost with Miscanthus and water and unfertilized peat (8.3 - 8.5 cm) and compost from Miscanthus and ammonium sulphate (5.5 cm). Dry weight per Hedera plant was highest for the fully fertilized peat (1.4 g), lower for composts with urea or pig slurry (0.9 – 1.0 g) and for composts with ammonium sulphate, or water and unfertilized peat (0.5 –0.6 g). For Fatsia dry weight was greatest with fertilized peat (1.8 g). Ammonium sulphate, and urea composts and unfertilized peat gave similar results (1.2 g), while pig slurry and water composts gave lowest dry weights (0.8 g and 0.5 g). Volumetric water content at suction of 10 cm water was greater for the fully fertilized peat (80%) than for the composts with pig slurry (60%) and ammonium sulphate (32%). Pig slurry resulted in high electrical conductivity (EC) and high concentrations of K, P, Mn, Na, Cl, Cu and Zn.
It was concluded that compost of Miscanthus plus a N-source is a potential substitute for peat.
Supraoptimal concentrations of nutrients in compost containing pig slurry may be overcome by using diluted pig slurry as nitrogen source.
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