New York Agricultural Experiment Station. 59 



at practically the cost of materials separately. In such cases there 

 may be some advantages in buying the mixed goods since it saves 

 the slight inconvenience of home mixing. But the difficulty here 

 is that the formula is seldom determined by those who know in 

 what proportions the three ingredients can be most profitably 

 used. For example take the Long Island formula 4-8-10 which 

 is put up especially for the potato growers of Long Island. This 

 formula is very generally used although experimental evidence 

 shows that it contains at least three times as much potassium as 

 is profitable. The large increase produced by bonemeal in this 

 experiment again testifies to the value of phosphorus. 



How to mix fertilizers. — If one has decided upon a certain number 

 of pounds per acre of each of two or more fertilizing materials, as 

 for instance 100 lbs. nitrate of soda, 300 lbs. acid phosphate and 50 

 lbs. muriate of potassium, then obviously he has only the very simple 

 problem of mixing these three materials in those proportions and 

 applying 450 lbs. per acre of the mixture. Indeed, it is hardly necessary 

 to make the problem of home mixing any more complicated than this. 



However, as the farmer begins to study more intently the subject 

 of fertilizers he will soon begin to think of pounds nitrogen, phos- 

 phorus and potassium per acre instead of pounds of the fertilizing 

 materials per acre. This method is, of course, more definite since the 

 different materials carrying nitrogen, phosphorus and potassium vary 

 greatly in the percentage of the fertilizing element which they carry; 

 but the problem is almost as simple as in the first case. The mixer 

 has only to compute the number of pounds of the purchased materials 

 needed to supply the quantities of the elements used per acre, by 

 dividing the number of pounds of each element required by the 

 percentage of it found in the material used. Suppose, then, he 

 decides to apply per acre 15 lbs. of nitrogen, 20 lbs. of phosphorus 

 and 20 lbs. potassium, and that he selects as materials to be used 

 nitrate of soda (15 per ct. N), acid phosphate (6f per ct. P = 15 per 

 ct. P2O5) and sulphate of potassium (40 per ct. K=48 per ct. K2O). 

 The computation will be as follows : 



Lbs. needed Percentage Lbs. of material 



Element. per acre. in material. to be used. 



N 15 -r- .15 = 100 nitrate of soda. 



P 20 -H .06f = 300 acid phosphate. 



K 20 -r .40 = 50 muriate of potassium. 



450 mixture. 



These materials are then mixed in those proportions, and 450 lbs. 

 (the sum) applied per acre. The arithmetic is sometimes more com- 

 plex than this, but in any case it is only a simple problem in percentage. 



If the percentages of the different elements in such a mixture are 

 desired, it is only necessary to divide the number of pounds of each 

 element by the whole number of pounds in the mixture. In the ex- 



