178 Agricultural Chemistry. 



pecially sensitive to acid conditions of the soil. This is probably 

 because such a medium is unfavorable for the activity of 

 nitrogen-fixing bacteria. This condition cannot develop in a soil 

 properly stocked with lime. 



The leguminous grain crops such as beans or peas are less ex- 

 hausting tft the minerals of the soil than are the hays of legumes, 

 for they develop a less extensive root system. These crops show 

 the same general distribution of constituents between the grain 

 and straw as do the cereal crops, and, as with the latter crops, 

 the greater part of the nitrogen and phosphoric acid is removed 

 in the seed. 



Requirements of root crops. The true root crops are pre- 

 eminently soil- exhausting crops. Not only do they assimilate 

 greater amounts of ash constituents per acre than the other 

 crops removed from the soil, with the exception of alfalfa, but 

 they remove more nitrogen than the cereals or grasses. In the 

 case of turnips, this amount of nitrogen is seen to be twice that 

 removed by cereal grains or meadow hay, and in the case of 

 mangels, it is three times as much as these crops contain. It is 

 important to realize that the root crops are entirely dependent 

 upon the soil for this important element of plant food. Potash 

 is uniformly conspicuous for its high proportion in the ash of 

 these crops. Its presence is explained by the fact already ob- 

 served, that this mineral is essential to the production of starch 

 and sugar, which are predominant compounds in these crops. 

 Since the amounts of phosphoric acid removed by these crops are 

 also uniformly high, it is apparent, as demonstrated also by prac- 

 tice, that they require especially complete and heavy manuring 

 when grown under intensive cultivation. 



Requirements of fruit crops. This class of crops is less ex- 

 haustive and less dependent upon immediate manuring than the 

 crops already discussed; the individual requirements will be 

 considered later. 



Requirements of forest growth. Timber growth exceeds most 

 of the other crops discussed in the annual production of dry mat- 



