ISHS Acta Horticulturae 450: International Symposium Growing Media and Plant Nutrition in Horticulture
IMPROVEMENT OF THE PHYSICAL CONDITIONS IN PEAT SUBSTRATES DURING THE GERMINATION OF CABBAGE SEEDS IN ORGANIC FARMING (REFEREED) |
| Author: | J. Willumsen |
| Keywords: | Brassica oleracea, propagation, plugs, porosity, aeration, water retention |
| Abstract:
A low content of air in propagation substrates may restrict germination and initial growth of seedlings. Possible ways to increase the air volume were investigated in two experiments where cabbage seeds were germinated in plug trays. The experiments comprised different combinations of substrate compaction, matric potential (suction) and seed coverage. A mixture of light and dark sphagnum peat, finely ground dolomitic limestone and composted poultry manure was chosen as propagation substrate. A loose substrate exposed to suction from a 6 cm 'layer' of sand or peat doubled the percentage of substrate air compared with a compressed substrate without suction. Significant relationships between air volume and seedling emergence were found. Suction and light compaction promoted a better and more even germination and initial growth. Covering the seeds with sand containing calcium carbonate gave a high percentage of inferior seedlings, but only when the air volume of the substrate was low. It is suggested that the uneven germination and emergence under conditions of inadequate aeration were caused by production of toxic levels of ammonia. | |
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