ACTIVE PLANT FOOD, ETC. 



Average 

 sibil 



Percentage of corn possibility 



nitrogen in soil (bushels per acre) 



O.OOO to O.O2 5-7 



O.O2I to 0.04 9.4 



0.041 to 0.06 13.6 



0.061 to o. 16 22.3 



o.i6itoo.i8 42.9 



Interpretation of Soil Analysis with Weak Solvents. The "corn 

 possibility" figures may be used for the purpose of ascertaining 

 the probable relative deficiency of a soil. Suppose, for example, 

 a soil contains .086 per cent, nitrogen, 8 parts per million active 

 phosphoric acid, and 105 parts per million active potash. 

 Referring to the tables, we find : 



Corn possibility 

 (bushels) 



For nitrogen 22.0 



For active phosphoric acid 4.5 



For active potash 102.0 



Thus this soil would probably be most deficient in phosphoric 

 acid, next in nitrogen, and least in potash, if tested in pot experi- 

 ments. 



The active phosphoric acid and potash and the total nitrogen 

 are not, however, the only things to consider under field con- 

 ditions. The form of the phosphoric acid, depth of soil, kind of 

 cultivation, season, etc., all influence the size of the crop. It is 

 thus not possible to say that the corn possibility represents what 

 should actually be produced in the field. Field results must be 

 worked out for different localities, as no doubt climate and tem- 

 perature will cause soils of the same analysis to give different 

 results in different sections. 



The fact that there is possibly a close relation between chemical 

 analyses and field results is shown in certain results secured at 

 the Texas Experiment Station. 1 Eight soils in which total 

 nitrogen was probably the controlling condition, averaged n 

 bushels per acre corn possibility, while the actual yield as claimed 

 by the farmers was 18 bushels. Five soils controlled by active 

 1 Proc. Int. Cong, of Applied Chem., 1912. 



