INTRODUCTION 



promotes friendly bacterial action. The produc- 

 tive power of most farming land is proportionate 

 to the amount of organic matter in it. The casual 

 observer, passing by farms, notes the presence or 

 absence of humus-making material by the color 

 and structure of the soil, and safely infers corre- 

 sponding fertility or poverty. Organic matter 

 is the life of the soil. 



A great percentage of the food consumed by 

 Europe and the Americas continues to come out 

 of nature's own stores in the soil, organic and in- 

 organic, without any assistance by man except 

 in respect to selection of seeds, planting, and till- 

 age. The percentage grows less as the store of 

 original supplies grows less and population in- 

 creases. Our science has broadened as the need 

 has grown greater. We have relatively few acres 

 remaining in the United States that do not re- 

 quire intelligent treatment to insure an adequate 

 supply of available plant-food. The total area 

 that has fallen below the line of profitable produc- 

 tiveness is large. Other areas that never were 

 highly productive must supplement the lands orig- 

 inally fertile in order that human needs may be met. 



When soils have been robbed through the greed 

 of man, nature is handicapped in her effort to 



[5] 



