198 Fruit-growing in Arid Regions 



where the swollen regions or tubercles are formed. This 

 low form of plant life is able to take the free nitrogen from 

 the soil-air and change it into forms that plants can use. 

 Consequently, legumes can be grown on land from which 

 nitrogen has been exhausted. 



It is also found that leguminous plants do not thrive in 

 soil where the accompanying bacteria are absent if the 

 nitrogen content of the soil is low. This led to the mak- 

 ing of pure cultures of the bacteria which are now sup- 

 plied in commercial form. These cultures, after being 

 diluted and after sufficient multiplication of bacteria has 

 taken place, are sprinkled % over the land; or better still, 

 seeds are soaked in the culture material just before plant- 

 ing. Such cultures have not been as successful as was 

 anticipated, and in the meantime a mass of overdrawn 

 articles on the subject has been printed in magazines and 

 papers. The result is that many farmers have been led 

 to think that by simply applying the cultures to their 

 land wonderful benefit will result to any and all crops. 

 The truth is, these cultures have no direct effect on any 

 plants other than the legumes. And, moreover, should 

 one wish to secure such material, he must designate the 

 particular crop he intends to grow. Cultures from clover 

 bacteria would not be expected to have any effect on beans 

 or alfalfa. It would be idle to apply these cultures to land 

 that is already producing good crops of any of these plants; 

 and, moreover, the whole subject is yet in an experimental 



How to use Shade-crops 



What crops shall be grown for shade-crops and how they 

 shall be handled, is a difficult question to answer, as the 



