218 ' ANNUAL REPORT OF THE Off. Dac. 



sold off the farm, because as barnyard manure, the plant substance 

 can be restored to the soil, and only as much nitrogen is lost 

 theoretically, as is removed in the animal tissues. One of the most 

 approved methods of agricultural practice is to grow leguminous 

 crops for home consumption and afterward nitrogen consuming 

 crops for sale. One practical farmer grows mixed crops of legu- 

 minous plants, liberally fertilized with potash and phosphoric acid. 

 He converts the first year's crop into silage, which he feeds to his 

 cattle, returning the manure to his soil and converts the second year's 

 produce into hay. The land thus produces highly nitrogenous crops 

 without manure and is left in a high condition for potatoes, or 

 cereal crops, which respond to dressings of nitrogenous fertilizers. 



Having ascertained these facts, the question naturally arises? How 

 can the growth of leguminous plants be encouraged? It has been 

 discovered, that leguminous crops require considerable supplies of 

 potash and phosphatic fertilizers. Potash has considerable to do 

 with the metabolism concerned in the formation of carbohydrates 

 and phosphorus compounds with the nitrogenous metabolism. The 

 writer was impressed by this fact in 1892 on a visit to the Roth- 

 amsted Experiment Farm in England. Whenever nitrogenous fer- 

 tilizers were supplied, there was a natural appearance of grasses 

 on the plots thus treated. Whenever potash replaced the nitrogen, 

 the grasses diminished and leguminous plants occupied the ground. 



From what has preceded, it becomes necessary to study the nodule 

 producing bacteria. Can these be added to the soil, or used so as 

 to increase the number of root nodules per plant? This has been 

 accomplished by the methods of pure culture. Pure cultures of the 

 various races of Rhizobium legurainosarura have been grown and 

 these have been introduced into the soil directly, or on the surface 

 of seeds previously dipped in the liquid-culture media. The United 

 States Department of Agriculture distributes these germs on cotton 

 previously soaked in the liquid culture media, but this method be- 

 ing open to certain objection, culture tubes of pure germ growths 

 are now being largely used. 



The following precautions should be observed in using the pure 

 cultures of the nitrifying organisms. Inoculation of the soil is de- 

 sirable, if it is low in organic matter and has not previously borne 

 leguminous crops, or if the legumes previously grown on the same 

 land have been devoid of nodules, or if the legume to be sown be- 

 longs to a species not closely related to one previously grown on the 

 same soil. For in order to prevent clover sickness, it is advisable to 

 grow in succession a variety of leguminous crops. Inoculation will 

 prove useless, if the legumes usually grown are producing average 

 yields, or, if the roots show nodules in abundance. If the soil is 

 rich in nitrogen, it is useless to inoculate the soil for few nodules 

 are formed under these conditions. Inoculation will be a failure, 

 if the directions are not carefully followed, or if the soil is acid 

 and in need of lime. In most cases failure will result, if the soil 

 needs fertilizers, such as potash, phosphoric acid or lime. In all 

 cases, it should be remembered that soil inoculation will not over- 

 come the results of bad agricultural practice. 



MR. SEEDS: Mr. Chairman, I would like to ask the Professor a 

 question. Professor, if I understand you right, I understood you 



