822 Sterilisation of Soil for Glasshouse Work. [Jan., 



longer, but after several years also has to go. Our experi- 

 ments show that this sick soil, after partial sterilisation, 

 can again be made to yield full crops. 



Methods and Cost of Partial Sterilisation. 



So far as the grower is concerned the whole problem 

 resolves itself into one of cost. The advantages of partial 

 sterilisation are : — 



(1) A greater utilisation of the plant food constituents of 

 the soil, resulting from the increased efficiency of the food- 

 making bacteria; 



(2) freedom from such insect and fungoid pests as reside in 

 the soil; 



(3) economy of soil and residual fertilising material, in 

 that spent soil, sick soil, &c, can be used again. 



These advantages do not appeal with equal force to all 

 growers ; they are worth very little to the man who is isolated 

 from all risk of infection and has abundance of virgin soil 

 and manure at his disposal ; they become more significant 

 where supplies of virgin soil and manure are more restricted, 

 or, what is the same thing, have to be paid for ; and, finally, 

 they become very important for cucumber growers who 

 annually sacrifice many tons of rich soil — some of it even 

 richer than farmyard manure * — because it is no longer 

 effective enough for them. 



It is obviously futile for us to consider any methods of 

 partial sterilisation that cost more than the advantages are 

 worth. Fortunately the maximum value can be fixed by the 

 value to the cucumber grower. The cost of wheeling out the 

 old borders and purchasing and carting in new soil is 

 variously estimated, but has been put by growers with whom 

 we have discussed the subject at 2s. to 3s. 6d. a ton in a 

 crowded district. In such a case the grower would still be 

 in pocket if he paid 2s. a ton to have his old soil treated, 



* Two cucumber soils analysed by us had the following composition : 









Farmyard Manure 









(Rothamsted 





Soil A. 



Soil B. 



average). 



Nitrogen 



075 



072 



0*64 



Phosphoric acid 



0*56 



073 



6*23 J 



Available phosphoric acid 



036 



0-46 



Potash 



o'54 



0*50 





Available potash 



0*12 



O'lO 



0'32j 



