466 Composition of Seaweed and Use as Manure, [sept., 



ance made for a possible stimulating effect of the iodides 

 present. 



In farm practice seaweed more or less takes the place of 

 dung, but there are several important differences. Seaweed 

 contains no fibre, and, consequently, does not produce the 

 black structureless material characteristic of the dung heap; 

 in decomposing it forms soluble substances which easily 

 wash away. For the same reason it decomposes more 

 completely than dung. It is even said to facilitate the 

 decomposition of dung on light soils and in dry districts, 

 but there is no very definite proof. 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. It also differs from 

 dung in its bacterial flora, but on this question so little is 

 known that any discussion would be premature* 



Experiments to test the manurial value of seaweed have 

 been made at Trondhjem, at the Rhode Island Experiment 

 Station, and by a few workers in Great Britain. In Mr. 

 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, 

 seaweed and superphosphate proved better 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 fullest effects, and systematic experiments | 

 could not fail to bring out some interesting results. 



Reference has already been made to the fact that seaweed 

 decomposes more completely than dung, and is converted 

 into soluble or gaseous substances. It should therefore not 

 be allowed to rot in heaps by itself, but should be put straight 

 on to the land, or, if this is not practicable, mixed with any 

 dung 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. 



Analysis shows that the seaweeds have not all equal 



