THE SOIL AND ITS IMPROVEMENT 101 



soil, the increase cf bacteria, the unlocking of plant-food, the 

 pulverizing of clods and the formation of a better seed bed 

 for garden seeds. 



10. Legume Nodules. — After peas, beans, or other legumes have 

 grown to a height of five or six inches in window boxes, or the garden, 

 a few plants should be dug with care to not pull the roots from the 

 soil. Rinse the roots in water and examine for nodules (Fig. 59). 



The nodules on legume roots of all kinds are the homes 

 of friendly bacteria. These bacteria enable the plants of this 

 family to secure nitrogen from the air in the soil about them. 

 When nitrogen is thus obtained it aids the grov^th of the crop 

 itself and also supplies nitrogen to other crops which follow 

 in the same soil. 



Unless 'nodules are present, the plants are not obtaining 

 nitrogen from air. Many soils do not contain the bacteria 

 required by different legumes for this purpose. It is often 

 found necessary to supply the bacteria by some process called 

 inoculation. 



11. Inoculating Soil for Legumes. — In two window boxes or 

 two perforated cans, or two similar plots in the garden, have the 

 soil and conditions alike with this exception: Let one be inoculated 

 with alfalfa bacteria. This is done by spreading on the surface of 

 the soil a little soil from a field or plot where alfalfa has grown 

 successfully, having nodules while growing. The inoculation soil is 

 to be raked into the surface immediately when applied, to avoid 

 exposure to bright sunshine. The sun would kill the bacteria. A 

 very small quantity of soil is enough. Inoculation may also be done 

 by using a culture obtained by writing to the Bureau of Plant Indus- 

 try, Washington, D.. 0. The directions which come with it sho"uld 

 be carefully followed. After inoculating one plot or box, each of 

 the two should be sown to alfalfa and allowed to grow until a few 

 inches high. Tlien a few plants may be -dug and the roots washed 

 and examined for nodules. The growth in the two plots should be 

 compared. Does this indicate that inoculation is helpful in the soil 

 you have? 



Some soils need inoculation for certain legumes, while 

 other soils have the bacteria present in abundance. Nearly 

 all good garden soils have plenty of bacteria suitable for such 



