ACTIVE PLANT FOOD, ETC. 



193 



have an average corn possibility of 4.5 bushels for phosphoric 

 acid and 58.6 bushels for potash. Evidently there is greater need 

 of phosphoric acid than of potash, and the two become equal by 

 the addition of sufficient phosphoric acid for 54.1 bushels corn. 



ACTIVE POTASH IN Son. //v PARTS PER MILLION 



Fig. 43. Relation of the potash removed by crops in pot experi- 

 ments to the active potash contained in the soil. 



This, however, is only an illustration. Field experiments must 

 show the exact relation of the two. 



Relation of Total Nitrogen to Results of Pot Experiments. 1 Pot 

 experiments similar to these just described have been used to 

 trace the relation between the total nitrogen of the soil and the 

 effect of the fertilizers. They will be described here on account 

 of their relation to the preceding work. The effect of the fertilizer 

 is, in general, related to the content of nitrogen in the soil. The 

 percentage of nitrogen in the crop increases as the percentage of 

 total nitrogen of the soil increases. The average corn possibility, 

 1 Texas Station Bulletin No. 151. 



