142 THE CULTURE OF FARM CROPS. 



tution ; and make available its natural fertility without add- 

 ing to it. 



But the study of these physical properties of soils is not 

 without an important practical value. For a farm may 

 have a fertile soil and be endowed with an abundance of 

 fit food for crops. It may have every provision for this val- 

 uable use, and yet its condition may be such that only the 

 lowest and most useless plants can support themselves upon 

 it It may produce reeds and rushes; sour unwholesome 

 sedges; useless moses and ferns, and weeds which are wholly 

 valueless for the support of animals, and yet the skillful 

 farmer knowing the principles which relate to the physical 

 properties of soils, may take such an undesirable farm and 

 by a judicious course of improvement may make a garden of 

 it, and wring from it the hidden stores of wealth w r hich lie 

 within it. But to do this he must recognize and understand 

 what the functions of the soil are ; that these are of two kinds 

 and each of these are distinct and separate but important 

 and necessary to the growth of plants. These are 



First. To uphold and sustain the plant and afford it a 

 safe and secure anchorage. 



Second. To absorb air, water and heat and retain these 

 for the promotion of the growth of crops. 



These are its mechanical and physical functions. 



Third. To supply to plants food of whatever kinds may 

 be required for the profitable growth of crops. 



Fourth. To give effect to all those chemical changes 

 which are required to produce the changes in the various 

 elements of this food by which they are prepared for admis- 

 sion into the roots and circulation of plants. 



These functions of the soil are performed in a very inade- 

 quate manner by nature, and while nature contributes the 

 materials, and the forces by which the materials may be 

 made available, yet the use and direction of these are left 

 to mankind, whose labor gives effect to them. And all the 

 operations of the farmer are intended to make these materi- 

 als and forces available; to* aid and assist in, and give full 

 effect to, the performance of these functions of the soil by 



