IMPROVING SOILS WITH LEGUMES 145 



alfalfa, or any other nitrogen-gathering legume accom- 

 panied by its particular form of bacteria, in a soil favor- 

 ing the bacterial life on the legumes, one is indeed in- 

 creasing one's nitrogen store very fast. 



The amount of nitrogen gathered will vary accord- 

 ing to the sort of plant grown, and then according as 

 the soil is fitted to make large growth of legumes. That 

 is, in order to help plants in their work of nitrogen gath- 

 ering, one should make the conditions as favorable as 

 possible in all things except supplying nitrogen. The 

 plant that comes to a soil rich in carbonate of lime, rich 

 in phosphorus and potassium, with air enough in it 

 and moisture enough, will gather a great deal more 

 nitrogen than one growing in a soil where any of these 

 factors are lacking. So if one wishes to enrich soil by 

 growing on it cowpeas, clover, or any legume, one 

 should begin by making it dry, by plowing well, and 

 then supplying what phosphorus may be needed. Thus 

 strengthened, the plants will gather very much more nitro- 

 gen than if they struggled to grow in a soil inhospitable 

 because waterlogged, hard or poor in phosphorus or pos- 

 sibly in potassium. 



Dr. Cyril G. Hopkins, experimenting with alfalfa (one 

 of the most energetic gatherers of nitrogen) tested plots 

 with inoculation against plots without, assuming that 

 the uninoculated plots got all their nitrogen from the 

 soil. He found that alfalfa, when supplied with lime 

 and phosphorus, gathered about 252 pounds of nitrogen 

 per acre, worth 15 cents a pound, or $37.80. In con- 

 trast a plot having no inoculation, and neither lime nor 



