GOOD SOILS BACK OF GOOD CROPS 13 



peculiar tendency of nitrogen makes it a very dif- 

 ficult element for the farmer to control. It is 

 costly. 



For a great many reasons we see that any method 

 or practice that will increase the store of nitrogen 

 in the soil will greatly improve its fertility. It has 

 been determined that all leguminous plants have 

 the peculiar power of fixing the free nitrogen gas of 

 the air, which exists in such great abundance, and 



FERTILIZING THE COWPEA 



No. 1. Phosphorus and potassium, but no nitrogen. 

 No. 2. Nitrogen, but no phosphorus and potassium. 

 No. 3. No fertilizers applied. 



changing it to the form of nitrates, in which form 

 it can be readily used by all species of plants. This 

 fixation is accomplished by means of a minute 

 micro-organism in the soil, which attaches itself to 

 the roots of these plants, causing the development 

 of a small tubercle or swelling, and inside this 

 tubercle or swelling the free nitrogen gas of the air 

 is changed to nitrates. So far as we know, the 

 leguminosae are the only plants that are able to 

 fix this nitrogen in quantities large enough to be of 



