SOIL TEXTURE AND COMPOSITION 



91 





j^doopoo lbs. Soil 





Nitrogen 



Phosphorus 



Potassium 



Logan (Greenville) 

 Nephi Dry-farm 



4,904 

 3,744 



2,700 

 8,388 



60,560 

 87,840 



These soils are below the average in nitrogen, above the aver- 

 age in phosphorus, and up to the maximum in potassium. The sur- 

 face foot of the soil of the Greenville farm contains sufficient 

 nitrogen for fifty-one 50-bushel crops of wheat, enough phos- 

 phorus for 169 crops, and sufficient potassium for 1,045 wheat 

 crops. The Nephi Dry-farm soil has sufficient nitrogen for 

 thirty-nine 50-bushel wheat crops, phosphorus for 523, and potas- 

 sium for 1,514 50-bushel wheat crops. 



It is, therefore, evident that in both of these soils the limiting 

 element in crop production is nitrosren which soon must be re- 

 placed; otherwise, ..aximum crops cannot be produced. The 

 time when the phosphorus will become the limiting element is 

 much more distant, whereas the potassium problem is one for the 

 future. The problem then which confronts the users of these 

 soils is to learn how to render the phosphorus and potassium avail- 

 able as needed by the growing plant and how to add the nitrogen 

 to the soil. This can be accomplished by means of soil bacteria. 

 Therefore, the present problem in soil fertility for these and 

 many other western soils is a problem in soil bacteriology. 



THE BIOLOGICAL AGENCIES IN THE SOIL 



The microorganisms of the soil are the means of maintaining 

 the nitrogen of our bank account of soil fertility and the means 

 by which we can unlock the phosphorus and potassium and obtain 

 it in the form of maximum crops. Hence, how many microor- 

 ganisms are there in the soil? Are there different classes? If 

 so, what are their functions? 



The microorganisms of the soil can be divided into two classes: 



