BIOLOGY O F SEAWEEDS O F ECONOMIC IMPORTANCE
217
in 14 days. By contrast Carpophyllum remained recognizable after
1 year. Macrocystis application increased the yield of dwarf beans.
Little (1953) reported on decomposition rates and manurial values of
some common brown seaweeds. Many of the earlier studies on the
manurial value of seaweeds were based on mineral analysis, but there is
evidence that seaweed application is not of value as a sole dressing.
Francki (1958) stated that manurial values should not be based solely
on mineral analyses. Thus application of dried Pachymenia and
Durvillea meal to soils of pH 6 or below resulted in the release of
manganese in toxic quantities. Francki (1960a,b), in further investigation of the manurial values of desiccated, sun-dried meals of Pachymenia himantophora and Durvillea antarctica, used tomato plants,
beetroot and radish as a means of bioassay. The general effects of
applying Pachymenia were found to be those associated with manganese toxicity and phosphorus deficiency, particularly in soils of low
pH where a noticeable depression of growth was observed. Results with
Durvilleu indicated metabolic changes normally associated with an
inadequacy of available nitrogen, suggesting an immobilization of the
element. Whilst Durvillea had no effect on soil consistency, Pachymenia
induced marked waterlogging of soil and a general impermeability.
From these results the suggestion was made that changes in ionic
milieu, physical structure, soil microorganisms and production of
growth-affecting organic compounds might follow dressing with these
marine algae. Milton (1964) has stated that direct application of seaweed meals does indeed cause an inhibitory action on plant growth, but
that this is overcome after a latent period of 15 weeks. In this initial
period the nitrate and ammonium contents of the soil diminish, suggesting selective growth of microorganisms, but this is followed by a
period of increased nitrogen content with a consequent stimulatory
effect on plant growth. Partial composting with loam and urea cuts
this induction period down to 14 days. Pressurized alkaline hydrolysis
and liquefaction had the same result as composting, and retained the
trace element content. Such an extract can be used as a direct soil
dressing or applied as foliar sprays. In general there is a marked
improvement in root growth and in crumb structure of the soil. The
beneficial effects of seaweed applications for their trace element content
has been commented on by Booth (1964b). Myklestad (1964) stated that
Laminaria hyperborea was more valuable as a soil dressing in Norway
on either newly cultivated ground or on soil in a poor condition ; its
value on well manured soil was far less marked. MacFarlane (1964b)
observed that fields in the Channel Islands dressed with seaweeds
showed marked water retaining properties during summer droughts.
217
in 14 days. By contrast Carpophyllum remained recognizable after
1 year. Macrocystis application increased the yield of dwarf beans.
Little (1953) reported on decomposition rates and manurial values of
some common brown seaweeds. Many of the earlier studies on the
manurial value of seaweeds were based on mineral analysis, but there is
evidence that seaweed application is not of value as a sole dressing.
Francki (1958) stated that manurial values should not be based solely
on mineral analyses. Thus application of dried Pachymenia and
Durvillea meal to soils of pH 6 or below resulted in the release of
manganese in toxic quantities. Francki (1960a,b), in further investigation of the manurial values of desiccated, sun-dried meals of Pachymenia himantophora and Durvillea antarctica, used tomato plants,
beetroot and radish as a means of bioassay. The general effects of
applying Pachymenia were found to be those associated with manganese toxicity and phosphorus deficiency, particularly in soils of low
pH where a noticeable depression of growth was observed. Results with
Durvilleu indicated metabolic changes normally associated with an
inadequacy of available nitrogen, suggesting an immobilization of the
element. Whilst Durvillea had no effect on soil consistency, Pachymenia
induced marked waterlogging of soil and a general impermeability.
From these results the suggestion was made that changes in ionic
milieu, physical structure, soil microorganisms and production of
growth-affecting organic compounds might follow dressing with these
marine algae. Milton (1964) has stated that direct application of seaweed meals does indeed cause an inhibitory action on plant growth, but
that this is overcome after a latent period of 15 weeks. In this initial
period the nitrate and ammonium contents of the soil diminish, suggesting selective growth of microorganisms, but this is followed by a
period of increased nitrogen content with a consequent stimulatory
effect on plant growth. Partial composting with loam and urea cuts
this induction period down to 14 days. Pressurized alkaline hydrolysis
and liquefaction had the same result as composting, and retained the
trace element content. Such an extract can be used as a direct soil
dressing or applied as foliar sprays. In general there is a marked
improvement in root growth and in crumb structure of the soil. The
beneficial effects of seaweed applications for their trace element content
has been commented on by Booth (1964b). Myklestad (1964) stated that
Laminaria hyperborea was more valuable as a soil dressing in Norway
on either newly cultivated ground or on soil in a poor condition ; its
value on well manured soil was far less marked. MacFarlane (1964b)
observed that fields in the Channel Islands dressed with seaweeds
showed marked water retaining properties during summer droughts.