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applied too closely to field conditions. One of such experiments 

 is reported in Bulletin 147 of the Rhode Island Agricultural Ex- 

 periment Station. Several different legumes were grown in spe- 

 cial flowerpots and the amount of nitrogen was determined both 

 in the plants and in the soil. The authors of the bulletin found 

 that all the different legumes that they grew were able to obtain 

 some nitrogen from the air. From their experiments they found 

 that an acre of soy beans may take about 1000 pounds of nitrogen 

 from the air during a period of five years, or 200 pounds per 

 year. Seven-tenths (140 pounds) of the 200 pounds were re- 

 moved in the crop, and three-tenths (60 pounds) remained in the 

 soil. Since one pound of nitrogen costs about 16 cents, 200 

 pounds would cost $32. 



We must be cautious and not jump at the conclusion that every 

 acre of soy beans or any other legume crop, grown in any soil 

 and under all kinds of conditions, would take out of the air an 

 amount of nitrogen worth $32. In some cases it may be done, 

 but in most cases such an amount of nitrogen is probably not re- 

 moved from the air by an acre of legumes. One thing is estab- 

 lished, however, and that is that the legumes with nodules on the 

 roots are enabled to use a certain amount of the atmospheric ni- 

 trogen and that the legumes without nodules are not able to do so. 



INOCULATION. 



We have learned from observations that nodules may not de- 

 velop on all the different legumes in all soils. From this we con- 

 clude that the bacteria which produce nodules are not always 

 present in every field. We find that legumes such as clovers, 

 which have been raised on almost every farm in this State for 

 many years, generally produce plenty of nodules in most soils. 

 Legtmies such as alfalfa, soy beans, and cowpeas, however, which 

 are relatively new crops in this State, do not generally produce 

 nodules. Since it is the bacteria that cause the nodules, and since 

 legumes without nodules are not able to get any nitrogen from 

 the air, it is to our advantage to introduce these nodule-forming 

 bacteria into our fields. Inoculation, therefore, is the introduc- 

 tion into the fields of the bacteria that cause, nodules on legumi- 

 nous crops. 



CROSS-INOCULATION. 



Can one legume be inoculated with the bacteria from a dif- 

 ferent legume? This qviestion is often asked by farmers. 



It seems to be well established that alfalfa can be inoculated 

 with the bacteria from sweet clover. Successful cross-inocula- 

 tion is obtained also between red clover, white clover, and alsike 

 clover. In general it may be stated that cross-inoculation takes 



