CHEMICAL ANALYSIS OF SOILS 55 



dition in the field. It is therefore impossible at present to draw any 

 certain conclusions from the results of such an analysis that are 

 applicable to field conditions. 



If, however, an analysis shows only a very small amount of nitrogen, 

 then one may conclude that the soil is deficient in this element and 

 will probably be benefited by its application. But this may be as 

 easily told by a simple inspection of the field while plants are growing. 

 A soil deficient in nitrogen is constantly showing its condition in the 

 plants. Short growth of straw and vine, failure to develop a full, 

 dark-green color, and the growth of sorrel and ox-eye daisy, all tell as 

 accurately as the chemist with all his skill that the soil lacks nitrogen. 

 And it is the same with the other constituents. It is only when a 

 soil is extremely deficient in certain plant-foods that an analysis shows 

 the cause of the trouble. 



The great majority of all soils, good and poor agriculturally, differ only 

 in narrow limits as to their composition. Every soil that yields well 

 does not contain more plant-food than one that yields less; on the 

 other hand, many soils that give poor yields are often rich : in plant- 

 food. 



Two samples of soil were recently examined in the chemical labora- 

 tory. On one of the soils alfalfa grows readily, on the other it has 

 failed. It might seem that the cause could be discovered by analyzing 

 the two samples. Following are the results : 



No. 1 , that does not grow alfalfa lAfo. 2, that grows alfalfa 



Nitrogen (N) . . 

 Phosphoric acid (P 2 O 5 ) 

 Potash (K 2 O) . . . 

 Lime (CaO) . . . 

 Magnesia (MgO) 



0.07 per cent Nitrogen (N) . . . 0.07 per cent 



0.12 per cent Phosphoric acid (P 2 O 5 ) 0.12 per cent 



0.14 per cent Potash (K 2 O) . . . 0.13 per cent 



0.17 per cent Lime (CaO) ... 0.20 per cent 



0.24 per cent Magnesia (MgO) . . 0.22 per cent 



Organic matter (humus) 3.45 per cent Organic matter (humus) 3.15 per cent 



Soils have an average weight of 2,000,000 Ib. per acre for a depth 

 of eight inches, and the composition of the two soils by weight is as 

 follows : 



No. 1 No. 2 



.07 N = 1,400 Ib. per acre. 0.07 N = 1,400 Ib. per acre. 



.12 P 2 O 5 = 2,400 Ib. per acre. 0.12 P 2 O 5 = 2,400 Ib. per acre. 



.14 K 2 O = 2,800 Ib. per acre. 0.13 K 2 O = 2,600 Ib. per acre. 



.17 CaO = 3,400 Ib. per acre. 0.20 CaO = 4,000 Ib. per acre. 



.24 MgO = 4,800 Ib. per acre. 0.22 MgO = 4,400 Ib. per acre. 



3.45 humus = 69,000 Ib. per acre. 3.15 humus = 63,000 Ib. per acre. 



