;HS 
l n*x ■ n ro 
UNITED STATES DEPARTMENT OF AGRICULTURE 
LLETIN No. 1280 
"been rev. 
— see rcv.ed* 
binders at 
Washington, D. C. 
October, 1924 
1 of file. &24J 
THE COMPUTATION OF FERTILIZER MIXTURES FROM CONCENTRATED 
MATERIALS 
By Albert R. Merz, Associate Chemist, and William H. Ross, Chemist, Bureau 
of Soils 
CONTENTS 
Page 
Introduction 1 
The triangular system for fertilizer mixtures 4 
Factors that influence the concentration of fertilizers fl 
Concentrated fertilizer compounds 7 
Standard fertilizer mixtures for concentrated materials 10 
INTRODUCTION 
The principal inorganic materials now used in the manufacture of 
fertilizers are acid phosphate, sodium nitrate, ammonium sulphate 
and various potash salts. All of these materials, which amount to 
70 per cent of the total consumed in the fertilizer industry in this 
country, have the feature in common that they contain but one 
fertilizing element. A number of organic materials such as cotton- 
seed meal, tankage, and fish scrap contain marketable quantities of two, 
or even all three, of the essential constituents of fertilizers ; but it often 
happens that the value of one of the constituents so much exceeds that 
of the others that the latter are frequently disregarded. The calcu- 
lation of the materials required in the manufacture of the great bulk 
of mixed fertilizers is therefore a comparatively simple matter. 
Thus, for example, the quantity of a material, such as ammonium 
sulphate with 25 per cent ammonia, required in a ton (2,000 pounds) 
of a fertilizer mixture to contain, say, 8 per cent of ammonia is 
simply obtained by multiplying the latter percentage by 2,000 and 
dividing by the former percentage (2,000x8/25=640). Or, in 
general, if a is the per cent of ammonia in the material, and A the 
desired percentage of ammonia in the complete fertilizer, then X 
Cthe quantitv of material required) is given bv the equation 
2,000^1 
a 
In the same way, the quantities Y and Z of the phosphoric acid 
and potash materials required in a complete fertilizer are given by 
the equations: 
Y =2,000-f and Z =2,000 - 
o c 
97378— 24f 1 
