PHOSPHATIC MANURES 233 



tity of phosphoric acid can, therefore, be applied to the 

 soil in the form of Thomas' phosphate, but the difference 

 in the results obtained is often very small when the 

 conditions are moderately well suited to the action of 

 both manures. When this is not the case, the difference 

 in favour of one or other may be very marked, and the 

 question as to which of the two should be preferred can 

 only be determined by experiment in each particular 

 case. 



Application of Basic Slag. Thomas' phosphate is com- 

 monly applied at the rate of from 5 to 10 cwts. per acre. 

 In the opinion of many men of large experience, anything 

 less than half a ton per acre is of comparatively little 

 use. In experiments conducted by the author, however, 

 on the application of basic slag to grass lands, it was 

 invariably found that, in the end, better results were 

 obtained by applying small quantities every year, than 

 by applying the same total quantity at a single dressing. 

 Basic slag is generally applied to grass in the back end of 

 the year or as early as possible in the spring in order that 

 it may become more thoroughly mixed with the soil. For 

 other crops it may be applied any time before sowing the 

 seed and harrowed in, but for roots better results are 

 obtained by applying it to the rows at the time of drilling 

 the seed than by broad -casting during the winter or early 

 spring. 



It should not be mixed with acids or acid salts, or even 

 with neutral salts which react with lime. For example, 

 if it be mixed with sulphate of ammonia the following 

 reaction takes place: 



(NH 4 ) 2 S0 4 + CaO = CaS0 4 + 2NH 3 + H 2 



Sulphate of Lime. Calcium Ammonia. Water, 

 ammonia. sulphate. 



This change, it will be seen, not only causes loss of 

 ammonia but also tends to destroy the basic character of 



