Commercial Gardening 



11. STERILIZING SOILS 



Of late years growers of Ferns, Cucumbers, Tomatoes, &c., have been 

 much concerned as to the best means of rendering their plants immune 

 from attacks of eel worm and other pests. The soil has been regarded as 

 the seat of all the mischief, and various nostrums have been boomed as 

 infallible remedies against all the diseases that attack market crops. 

 At first some of these remedies appeared to check the disease, but after 

 a time the trouble was as rampant as ever. The only things that have 

 not been tried are cultivation and common sense. Soils have been brought 



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into cucumber houses at great expense, and have been dosed with rich 

 organic and chemical manures to such an extent that acidity becomes 

 one of the predominant features. Under a high temperature, 85 to 95 F. 

 and more, and an excessively humid atmosphere, trillions of bacteria are 

 brought into being. Bearing in mind what has been said at p. 127 about 

 nitrate-forming bacteria growing lazy owing to having too much nitro- 

 genous food at their disposal, it is not to be wondered at that they fail 

 to perform those beneficial duties which they carry out in a soil con- 

 taining only a reasonable amount of organic material. Other bacteria, 

 no doubt, then come into play and doubtless devour the lazy ones, and 

 bring about such a condition of the soil that other troubles, like eelworms, 

 arise and play havoc with the roots of plants. 



This being the case, the simplest plan would appear to be to keep 

 the soil from becoming acid by giving less rich food and more lime 

 the latter not only to counteract acidity, but also to induce the beneficent 

 bacteria to carry on their work. In addition to this, plenty of fresh air 

 must be admitted when possible, according to the state of the weather, 

 because the bacteria must have fresh supplies of oxygen to encourage 

 their activity. Many plant houses are so poorly ventilated that they 

 become "stuffy" with the stale atmosphere in them. 



Burning- and Steaming- the Soil. Where a rational system of 

 cultivation is not practised, recourse is had to steaming or burning the 

 soil. Many growers of Ferns, for example, place the soil in receptacles 

 of some kind, and have it burned in the furnaces before sowing spores 

 upon it. The idea is that the excessive heat kills all the " bad " or un- 

 friendly bacteria and leaves the good or friendly ones intact. It has been 

 stated that bacteria are killed outright at 195 F., and that they cease 

 to work, and become comatose or unconscious, at 132 F. Consequently, 

 when soil is heated to 200 or 300 F. it follows that the bacteria must 

 be killed right out, and the soil reverts to a more or less sterile condition. 

 Because, in addition to killing the bacteria, if the heat is too intense all 

 organic material will be driven off also, leaving only the mineral substances 

 of the soil. This result can be achieved without burning, simply by crush- 

 ing pieces of brick or mortar, and sowing the spores upon them, as many 

 growers do. 



