The Latent Period:
The second effect of adding seaweed or seaweed meal, to a soil well populated with bacteria, has already been mentioned briefly. It is a more complex matter, and requires consideration in some detail. Basically, the addition of seaweed leads to a temporary diminution of nitrogen available for crops, then a considerable augmentation of the nitrogen total.
When seaweed, or indeed any undecomposed organic matter, is put into the soil, it is attacked by bacteria which break the material down into simpler units -- in a word, decompose it. To do this effectively the bacteria need nitrogen, and this they take from the first available source, the soil.
This means that after seaweed has been added to the soil, there is a period during which the amount of soil nitrogen available to plants is reduced. During this period seed germination, and the feeding and growth of plants, can be inhibited to greater or lesser degree.
[liquid seaweed extract is not subject to this latent period but lacks the vitamins of the fresh & dried seaweed. IMB
This temporary nitrogen deficiency is brought about when any
undecomposed vegetable matter is added to the soil.
In the case of straw, for example, which is ploughed in after harvest, bacteria use up soil nitrogen in breaking down its cellulose, so that a 'latent' period follows. Farmers burn stubble after harvest to avoid this latent period, and the short-term loss of available nitrogen which causes it. But such stubble-burning is done at the cost of soil structure, soil fertility, and long-term supplies of nitrogen which ultimately would have been released from the decomposed straw.
...during this "Latent period" there is a temporary shortage of available nitrogen, while the total nitrogen in the soil is actually being increased.
This increase makes itself felt after the seaweed is completely broken down. Total nitrogen then becomes available to the plant, and there is a corresponding upsurge in plant growth.
It is therefore clear that while seaweed, in common with all organic matter, is beneficial to soil and plant, it has to be broken down, or decomposed, before its benefits are available.
( that liquid seaweed extract is not subject to this latent period.
The nutrients and other substances it contains are available to the plant at once.)
"The Chilcott Method":
This period of decomposition -- or composting, as gardeners know it -- usually extends over months. It can, however, be reduced by the use of dried blood and loam according to the technique created by a Mr. L. C. Chilcott
Only fourteen days of heating up are required before the mixture is used, and no latent period follows.
which are the ones used in agriculture and horticulture, not only contain vitamins common to land plants, but also vitamins which may owe their origin to bacteria which attach themselves to sea plants, in particular vitamin B12. There is still some doubt about this -- B12 may be contained in the seaweed, although in some cases it is in associated bacteria.
Vitamins known to be present in the brown seaweeds include vitamin C (ascorbic acid), which appears in as high a proportion as in alfalfa.
Vitamin A is not present, but its precursor, beta-carotene, is, as well as fucoxanthin, which may also be the precursor of Vitamin A.
B group vitamins present are B1 (thiamine), B2 (riboflavin), B12, as well as pantothenic acid, folic acid and folinic acid.
Also found in brown seaweeds are vitamin E (tocopherol), vitamin K, and other growth-promoting substances. The unusual nature of the vitamin E in seaweed should be stressed. It has valuable characteristics (put technically, a complete set of isomers) found only in such seed oils as wheat germ oil.
Auxins in seaweed include indolyl-acetic acid, discovered in seaweed in 1933 for the first time. Two new auxins, as yet unidentified, but unlike any of the known indolyl-acetic acid types, were also discovered in 1958 in the Laminaria and Ascophyllum seaweeds used for processing into dried seaweed meal and liquid extract.
These auxins have been found to encourage the growth of more cells -- in which they differ from more familiar types of auxin which simply enlarge the cells without increasing their number.
One of the auxins also stimulates growth in both stems and roots of plants, and in this differs from indolyl-acetic acid and its derivatives, which cause cells to elongate but not to divide.
The balanced action of this seaweed auxin has not been found in any other auxin...
...At least two gibberellins (hormones which simply encourage growth, and have not, like auxins, growth-controlling properties too) have been identified in seaweed. They behave like those gibberellins which research workers have numbered A3 and A7 -- although they may in fact be vitamins A1 and A4.