224 PASTORAL AND AGRICULTURAL BOTANY > 



ous metabolism. This fact was impressed upon the writer on a visit to 

 the Rothamsted Experiment Farm in England in 1892. Experiments at 

 Rothamsted have demonstrated that whenever nitrogenous fertilizers 

 were supplied to the plots of herbage, the grasses increased in number and 

 abundance. Whenever potash replaced the nitrogen, the leguminous 

 plants began to invade the experimental plats. The student having 

 followed the above discussion may ask the question, if it is not possible 

 to introduce the proper organism, namely, Bacillus radicicola to the soil 

 in order to render more certain the inoculation of the leguminous plants 

 grown either for forage, for human food, or for green manure, as the 

 leguminous plants through the activity, of the nodule-forming bacteria 

 are supplied with a source of nitrogen not available to most other plants? 



Microbe-Seeding. Where nitrogen-fixing bacteria are lacking in a 

 soil, it is possible to introduce them artificially either by transferring soil 

 from an old field, where the desired leguminous crop has been grown suc- 

 cessfully, or by the use of pure cultures of the proper organism. The 

 method of transferring soil is inconvenient and expensive, and the use of 

 the preparation nitragin has not been a success. The organisms grown 

 upon nitrogen-free media have been found beneficial, if added directly 

 to the soil, although negative results are obtained, if the soil already con- 

 tains the proper bacteria, or if the soil is acid, needs fertilizers, such as 

 potash, phosphoric acid, or lime, and is so rich in nitrogen as to prevent 

 the development of the nitrogen-fixing organism. 



Nitrogen-consuming Plants. The point of interest to remember is 

 that the preceding leguminous, nitrogen-storing crop prepares the soil, 

 if used as a green manure, for the succeeding nitrogen-consuming crops, 

 which need their nitrogen in the form of nitrates. Agriculturally speak- 

 ing there are eight groups of nitrogen-consuming plants which may be 

 distinguished : the root, bulb, stem, leaf, flower, fruit, seed, and cereal crops. 

 All of these crops need nitrogenous substance for their best development, 

 because sugar, starch and other carbohydrate reserve materials are only 

 stored in the plant when nitrogen is present in efficient supplies. The 

 proper storage of the various carbohydrates can take place only when the 

 storage cells are supplied with the requisite amounts of nitrogen and 

 potash. If the plant is nitrogen hungry, such carbohydrate reserve 

 supplies are not formed. As a large number of plants used by man and 

 grown in various parts of America in horticultural and agricultural opera- 

 tions have been omitted purposely in order to keep this book within 



