SEA BA.M1!:)(^ AS A SOUKClv t)F POTASH. II3 



of possibility that in time the huge quantities of seaweed which 

 are at our disposal may be used not only to supply our own 

 needs in this respect, but to furnish raw materials for industries 

 at present dependent upon oversea supplies. 



It is a question for practical investigation whether, when 

 used for fertilisation, it should be applied as harvested or after 

 being ashed. The Board of Agriculture and Fisheries, in the 

 leaflet quoted above, recommend its direct apphcation to land, 

 remarking that : 



Seaweed contains about as nnich nitrogen as farniyaul manure, but. 

 as it is present as slow acting organic nitrogen, it is scarcely so valuable 

 as in average dung in which a certain proportion is present in the active 

 available form of soluble ammonia compounds. As the seaweed decays 

 rapidly in the soil, however, some of its nitrogen soon becomes available. 

 The amount of phosphate in seaweed is only about one-half or one-third 

 that of dung; on the other hand seaweed is on the average considerably 

 richer in potasli. It will be seen, therefore, that it is desirable as a rule to 

 supplement it with a phosphatic manure. Seaweed contains no fibre. 

 and, consequently, does not produce the black fibrous material character- 

 istic of the dung-heap ; in decomposing it forms soluble substances which 

 easily wash away. For the same reason it decomposes more complete!}' 

 than dung. It is even said to facilitate the decomposition of dung on light 

 soils and in dry districts, but there is no definite proof of this. A ton of 

 dung and seaweed would break down in the soil more quickly than a ton 

 of dung alone and would therefore have less of a drying effect if put on 

 late. The freedom of seaweed from weed seeds and from spores of 

 disease organisms is of considerable advantage on light soils where weeds 

 are common, or on soils liable to such diseases as finger-and-toe, the spores 

 of which can hardly be kept out of dung. 



Experiments to test the manurial value of seaweed have been made 

 at Trondlijem, at the Rhode Island Experiment Station and by a few 

 workers in Great Britain. In Hendrick's trials seaweed proved fully as 

 effective as dung for early potatoes, so far as quantity of produce was 

 concerned, but it somewhat retarded ripening. On the other hand, sea- 

 weed and superphosphate proved l:'etter than dung and superphosphate. 

 It is, however, on such gross feeding crops as mangolds and the cabbage 

 tribe that seaweed would be expected to show its fulK st effects. 



Reference has already been made to the fact that seaweed decomposes 

 more completely than dung, and is converted into soluble or gaseous sub- 

 stances. It should therefore not be allowed to rot in heaps by itself. l)Ui 

 should be put straight on to the land, or. if this is not practicable, mixed 

 with dung or other material which will absorb some of the decomposition 

 products. The value of a heap of seaweed is much lessened by exposure 

 to rain but exceptions to this rule may arise in the case of special garden 

 crops. 



Juritz (loc. cit.) says: — 



Nothing being thus, as a rule, gained by making compost with sea- 

 weeds or allowing them to ferment, the practice generally is to employ 

 such articles as a green manure by way of top-dressings, or to plough 

 ^hem into the soil while fresh, rapid deca\ resulting in the production of 

 speedy effects on the crops; whvle, in consequence of their prolific growth. 

 each succeeding season is likely to place ready to h;ind a fresh su])ply of 

 seaweeds. 



So rapid, indeed, is tlie growth of seaweed that at a spot on the 

 Scottish coast where all the growing seaweed had been removed, within 

 six months there was again :i thick .growth of ribbon kelp two feet, long, 

 and of ordinary kel)i six feel long. 



