Gardening for Amateurs 



521 



Sterilisation of the Soil 



THE Object. When sterilising soil 

 we do not aim at rendering it 

 sterile ; it should really be our 

 desire to remove from it all potential 

 pests, all vegetable or animal life which 

 will do harm to our crops or usurp the 

 place of our plants. An average sample 

 of soil may contain insects in either the 

 active or quiescent state, tiny eggs which 

 will hatch into insects, seeds of various 

 plants, spores of fungi, lichens or liver- 

 worts, and a large number of bacteria or 

 germs, many of which might carry disease 

 to our crops ; every one can do more or 

 less harm to the garden products, and the 

 aim of soil sterilisation is to remove them 

 all. In horticulture, then, sterilisation is 

 not a process carried to the ultimate de- 

 struction of the fertility of soil, so render- 

 ing it barren ; it is 

 really a partial 

 sterilisation, never 

 too drastic, in case 

 we make the soil 

 poisonous to our 

 plants. It must 

 not destroy the 

 humus which deter- 

 mines the richness 

 of the ground, and 

 it should stop short 

 of killing the micro- 

 organisms engaged 

 in nitrification, or 

 reducing the humus 

 to soluble nitrates 

 for plant food. 

 Total sterilisation is 

 most unwise, partial 

 sterilisation almost 

 a necessity, in 

 modern gardening. 



Methods of Steri- 

 lisation. The pro- 

 cess of sterilisation 

 may be carried out 

 in various ways. 

 Many gardeners find 

 physical methods 



PERFORATED GALVANIZED PLATES 

 FOR SHELVES 





A simple apparatus, made of zinc or 

 galvanised iron, for the sterilisation 

 of soil in flower pots. 



best for the operation ; heat is perhaps the 

 most common of these, and if carefully 

 carried out is the best method yet devised ; 

 great cold would be equally effective, and 

 it is a wise plan to ridge up the soil and 

 let frost penetrate through it. Such means 

 involve more or less labour, hence easier 

 chemical methods have come into wide 

 practice ; in this case substances evolving 

 a powerful fumigating gas are worked into 

 the soil. Sometimes it is a poisonous 

 liquid or solid which is used, and which kills 

 all life with which it comes in contact ; 

 or, again, it may be a chemical which com- 

 bines with some of the soil constituents 

 and so becomes insecticidal or fungicidal 

 in action. 



PHYSICAL METHODS 



Scalding. Of all the methods yet tried 

 the best is to heat 

 the soil to a certain 

 temperature. Great 

 care must be exer- 

 cised in the work ; 

 in fact, all soil steril- 

 isation should be car- 

 ried out cautiously, 

 and if the proper 

 temperature is not 

 exceeded the re- 

 quisite functions will 

 be performed and 

 the useful soil bac- 

 teria, the humus, 

 and other valuable 

 ingredients scarcely 

 altered. A simple 

 plan is to scald the 

 soil with boiling 

 water ; this is a 

 handy and valuable 

 way of dealing with 

 composts used in 

 potting, for frames, 

 and in small bulk. 

 The soil which is to 

 be treated is spread 

 out on a bag or a 

 sieve, or perhaps 





