226 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



Russell and Hutchinson on soil sterilization. They found that 

 after the soil had been sterilized plants grew very vigorously in 

 it. The reason for this vigorous growth is probably that owing to 

 intensive cultivation the bacterial flora had got out of balance, and 

 that a certain comparatively big amoeba that feeds on the beneficial 

 bacteria had got the upper hand. 



Owing to its larger size, this amceba is more vulnerable, and 

 suffers more than the beneficial bacteria from the sterilization ; con- 

 sequently, after that operation, the latter, being relieved to a large 

 extent of the preying of the amceba, are able again to flourish, with the 

 result that they carry on their work more vigorously than ever, and 

 large quantities of dormant food material are again prepared for the 

 plant. 



The reason why I have mentioned this is that the work of the 

 Americans goes to show that the mineral manures act on the soil 

 as a partial sterilization : that is, to bring about to a slight extent 

 the state of things to which I have just referred ; and for this reason 

 they are beginning to regard them as useful, mainly for combating 

 the soil toxins. 



This is a most interesting theory, and if correct — as there seems 

 every reason to believe — provides a further instance of the use of 

 minerals. 



The practical conclusion of the matter is therefore probably 

 this :— 



Use organic manures as a base to supply humus, and thus improve 

 the texture of your soil and enable you to get a good tilth and a 

 good seed-bed, to give you gradual feeding of the crop, which 

 promotes healthy growth and good quality, and to provide humus 

 to feed bacteria. 



Use mineral manures as a top dressing for rapid growth, and to 

 act as a sterilizer to keep the bacterial flora in balance. 



