PLANTS AND OURSELVES 17 



knowing why plants behave as they do ; why the doing of 

 certain things produces good results, and why the doing 

 of other things produces poor results. Farms cannot be 

 run best by rules alone. Each field is a problem in itself, 

 and the farmer needs to know how to solve his problems 

 for himself. To do this he must understand the principles 

 of plant life. He must understand the conditions which 

 are most favorable to plant growth, and learn to recognize 



Corn standing in shocks. 



what conditions are unfavorable to it. He must under- 

 stand why it is that crop plants gradually poison the soil 

 for themselves, and why it is an advantage to change 

 the crops. He must understand why plants of the clover 

 family increase the fertility of the soil, and why it is that 

 deep plowing and frequent crumbling of the surface also 

 increase it. He must understand the relation of water 

 to plant life, and why drainage increases fertility. He 

 must understand the principles which should guide him in 



