206 



different times of the year, indicate that weed cut in October is 

 poorer than that cut in March or May. His results are: 



Average 

 Per Cent. 



75 

 18 



1.2 

 0.09 



British results are summarised as follows, the sea-weed examined 

 being in the wet condition: 



Per Cent. 



Water 70 to 80 



Organic Matter . . . 13 to 20 



Nitrogen 0.3 to 0.8 



Potash 0.8 to i.o 



Phosphoric acid . . 0.02 to 0.17 



A considerable amount of water is lost on drying in the air, 

 and if the weed has not been washed by rain in the meantime, its 

 value is increased four, five, or even six fold. 



It is difficult to form an estimate of the money value of seaweed 

 to the farmer. The fertilising materials present in i ton of seaweed 

 possessing the average composition would cost 8s. to zos. if pur- 

 chased from a dealer. This value is arrived at by allowing 125. 

 for each per cent, of nitrogen, 45. for each per cent, of potash, 

 and 35. for each per cent, of phosphoric acid. No account is 

 taken of the sodium, calcium and magnesium salts, which on most 

 soils, but especially light soils, would be distinctly beneficial; nor 

 is any allowance for a possible stimulating effect of the iodides 

 present (i). 



(i) In a recent dispute on the value of seaweed at Rosyth, the values 

 assigned by experts to sea-weed varied from is. per ton to 95. 3 1 /., d. In the 

 end the arbitrator fixed the value at 43. gd. 



See North British Agriculturist, quoted in Nature, Aug. 4, 1910, p. 151. Ed. 



