ISHS Acta Horticulturae 51: Symposium on Protected Cultivation of Flowers and Vegetables
FLOWER CROPS IN PEAT SUBSTRATES |
| Author: | R.D. Pollock |
| Abstract:
The climate of Guernsey is well-suited to glasshouse crop production (table 1). Winter light is relatively good compared with other parts of N.W. Europe. The island has an equable climate : mild winters which mean lower fuel demands in the winter and cool summers which enhance summer flower quality. Horticulture's contribution of 35% to the total export earnings is a major factor in the Island's economy. Floriculture earning in the region of £6 million contributes 30% of the horticultural revenue (table 2). The three most important flower crops in the island are roses, freesias and iris. Roses are invariably grown in the soil although on many sites soil conditions are not perfect for roses; iris are generally planted directly in the glasshouse border; a proportion of the freesia crop is grown in containers stood outside and moved under glass before flowering. Carnations are increasing in area and value. Generally they are grown in border soil which receives expensive chemical and steam sterilisation between crops to eliminate Phialophora (Verticillium) cinerescens and Fusarium oxysporum. Trials have shown that worthwhile crops of Gerbera can be grown in Guernsey (1). However wilt disease and foot rots can be a serious problem with this crop. Where diseases are known to be soil-borne there could be considerable advantages of soilless substrates could be used. Freesias have been grown in 230 mm bitumenised containers using JIP composts and stood out on specially prepared standing out areas covered with gravel overlying black polythene sheeting (2). It has become increasingly difficult to obtain loam of the required standard (3). Research studies have shown that peat is a suitable medium for growing plants. Penningsfeld (4) in an article summarising eight years studies on the uses of peat suggested the following advantages over soil : freedom from disease, stimulation of growth, particularly root growth and the enhancement of availability of minor elements. Puustjarvi (5) concluded that sphagnum peat of good quality is very much the ideal growing medium. Is has very desirable physical properties : 95 – 97% pore volume or looked at the other way round 3 – 5% of the volume is solid material; it is surface active having a cation exchange capacity of 20 – 100 me l-1 it has a low bulk density 50 –70 kg m-3; it is moisture retentive with about 30% easily available water. Microbiological studies (Küster, 6) have shown that peat is not merely a sterile and biologically inactive substrate used only for its water-Holding capacity. It contains a wide range of organic compounds : auxins, hormones, vitamins, antibiotics etc. | |
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