SOME GENERAL PRINCIPLES 53 



In many soils the germs which produce nodules 

 are present when clovers are first grown on them. 

 But where they are not present, the clover plants 

 have no more power to gather nitrogen than wheat 

 or other non-leguminous crops. But since in other 

 soils they are almost entirely absent, how shall they 

 be introduced ? The process of introducing them is 

 generally referred to as a process of inoculation, and 

 soils when treated successfully are said to be inocu- 

 lated. 



Three methods have been adopted. By the first, 

 as previously indicated, the grower perseveres in 

 sowing clover at short intervals in the rotation. He 

 may also add farmyard manure occasionally, and 

 v.ms, through the inherent power of multiplication in 

 the bacteria, they increase sufficiently to enable the 

 land to grow good crops. By the second method, 

 inoculating is effected through soil which is pos- 

 sessed of the requisite bacteria ; and by the third, it 

 is effected through the aid of a prepared product 

 named nitragin. 



When fields are to be inoculated by using soil it is 

 obtained from areas which have grown clovers suc- 

 cessfully quite recently, and which are, therefore, 

 likely to be well filled with the desired bacteria. In 

 some instances the seed is mixed with the soil and 

 these are. sown together. To thus mix the seed with 

 the soil and then sow both together broadcast or 

 with a seed drill is usually effective, and it is prac- 

 ticable when minimum quantities of soil well laden 

 with germs are used. In other instances the soil 

 containing germs is scattered broadcast before or 



