1921.] Phosphatic Manures. I NT 



range roughly from 16 to 32 per cent, total phosphates; few 

 range above that figure, and several are below it. When it is 

 remembered that a few years ago high grade slags approximated 

 to 40 per cent, total phosphates, it is obvious that dressings of 

 a 20 per cent, slag must be doubled in quantity to effect the 

 same improvement. Industrial conditions resulting in short 

 time being worked in the steel works may prove a further 

 factor in limiting output. It would seem important, therefore, 

 to confine the use of slag mainly to grassland, and make up 

 the phosphates required elsewhere by dressings of other 

 manures. There are cases where slag appears to confer no 

 benefit on poor pasture, and it seems questionable whether, 

 where that is so, any other form of phosphatic manure would 

 do better. It is worth mentioning, however, that an absolute 

 lack of potash in some soils may prevent any visible result 

 from dressings of phosphates, while on other soils a rough, 

 matted and fibrous covering greatly handicaps the slag in 

 reaching the soil. A very thorough harrowing is imperative to 

 set this condition right. 



The second consideration is the possibility of substituting 

 superphosphates for basic slag in order to take advantage of 

 the state of supplies. Local experience or experiment may 

 prompt the use of superphosphates on grassland in place of 

 slag. Approximately 5J cwt. of 85 per cent, superphosphate 

 equals a dressing of 5 cwt. high-grade basic slag. Generally, 

 superphosphate may be substituted where it has been 

 customary to use slag in cropping: the former is more rapid in 

 action and thus, as a rule, better suited to arable farming. In 

 consequence of this rapidity, its maximum effect is more 

 quickly reached, but where seeds are only down for one year, 

 the influence of this manure applied to the nurse crop will be 

 all that is required. Where there is hesitation to substitute 

 superphosphate for slag altogether, the two may be mixed. 

 Superphosphate will act rapidly on soil with a good lime 

 content. 



Thirdly, there is the use of phosphatic manures other than 

 those already discussed. A review of experiments conducted 

 in this country shows that finely ground mineral phosphate is 

 valuable in the north of England and also in Scotland and in 

 Wales. Good results have also attended its use in Essex, and 

 has been applied also with benefit in other districts, notably 

 in those with a high rainfall, and on soils rich in organic 

 matter. 



