.THE USE OF COMFREY (SYMPHYTUM X UPLANDICUM) AS A SOURCE OF PLANT NUTRIENTS
.1 2. h 2 d 1
P.J.C. Harr1S , W.F. Bourne, C. G1tS am an M. Lennartsson
1 bl . . Henry Dou eda¥ Research Assoc1at10n, Ryton-on-Dunsmore, Coventry CV8
3LG, England. Department of Biological Sciences, Coventry Polytechnic,
priory Street, Coventry CV1 5FB, England.
ABSTRACT
Methods for the production of comfrey (Symphytum x uplandicum) liquid
fertilizer and comfrey leafmould are described. Comfrey leaves
decomposed rapidly to give a liquid fertilizer. The concentration of
nitrogen, phosphorus and potassium in the liquid varied between
successive harvests. In trials with radish (Raphanus sativus), liquid
from the first harvest of comfrey leaves in spring gave significantly
greater yields than did two commercial organic liquid fertilizers. In
trials with tomato (Lycopersicon esculentum), with the combined liquid of
all the harvests for one year, yields with comfrey liquid did not differ
significantly from two commercial organic feeds but were significantly
lower than two inorganic liquid fertilizers. The combined comfrey liquid
had higher potassium but lower nitrogen and phosphorus concentrations
than the liquid from the first harvest. In separate trials tomato
plants were grown in a potting compost made by mixing comfrey leaves and
leafmould and the yields compared with those obtained with four commercial
organic composts. In 1988 two of the commercial products gave higher
yields than comfrey leafmould, whereas in 1989 only one of the commercial
products gave a significantly higher yield. It is concluded that comfrey
gives high yields of leaf material and liquid fertilizer. It is a rich
source of nutrients containing particularly high levels of potassium.
...
CONCLUSIONS
Fresh comfrey leaves rapidly decompose, without the addition of water, to
give a high yield of a liquid fertilizer. However, the fertilizer value
of this liquid is very variable depending on the date of harvesting the
comfrey leaves and possibly on the stage of the plant life cycle. Comfrey
liquid is a rich source of potassium but additional source of organic
nitrogen may be ncessary to produce a balanced fertilizer. Comfrey
leafmould is a good balanced nutrient source for composts and compared
favourably with commercial organic potting composts for use by the amateur
gardener.
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