April, 1913 



THE CANADIAN HORTICULTURIST 



101 



The Sterilization of Soils^ 



A. H. MacLennan, B 



The spread of many diseases and in- 

 sect pests within the soil in the green- 

 house has turned investigation work to 

 find a solution. Perhaps the commonest 

 example is the eel-worm or Nematode 

 (Heterodera), which affects the roots of 

 indoor tomatoes and Damping-off Fun- 

 gus (Pythium), which destroys many 

 seedlings. 



Two results are very noticeable after 

 sterilization : First, disease organisms 

 and pests are killed or greatly reduced 

 in numbers ; second, while many of the 

 bacteria in the soil are destroyed, those 

 whose presence is beneficial remain, be- 

 come much more active, and plant food 

 is made more rapidly. 



In a bacterial count of soil — sterilized 

 and unsterilized — made by the Bacterio- 

 logical Department of the College last 

 year, the following results were ob- 

 tained : 



1 . Unsterilized — One million six hun- 

 dred thousand bacteria per cubic centi- 

 metre . 



2 . Sterilized — (a) in first two inches 

 of soil, temperature two hundred and 

 ten degrees, nine hundred bacteria p)er 

 cubic centimetre ; (b) at depth of six 

 inches, temperature one hundred and 

 seventy degrees, six hundred bacteria 

 per cubic centimetre. 



In number two the bacteria that re- 

 maijied were beneficial and aided in 

 breaking down the plant food in the 

 soil. The action of sterilizing is shown 



.S.A., O.A.C., Guelph 



in the sturdier growth of the plants and 

 their darker color. 



Two methods are in use to-day, — 

 steam and chemicals, the chief being 

 formaldehyde and Toluol. The work 

 with chemicals has been but little tried 

 in this country, but in England has so 

 far not given quite as good results as 

 steam. 



■ METHODS OP STERILIZING 



There are three methods of steam 

 sterilizing: First, by underground tile, 

 the method explained by Mr. Streight 

 in the February, 1912, number of The 

 Canadian Horticulturist. This method 

 is very easy where one uses sub-irriga- 

 tion. 



Second, by the laying of a system of 

 three three-quarter inch iron pipes like 

 this: 



*OQtUii« of an addreflR deMTered Teoentl^ be- 

 fore the Toronto Branch of the Ontario Vege- 

 table Qrowems' Aeaociation. 



placed eight to nine inches under 

 ground. In each side of each pipe, there 

 are one-eighth to one-quarter inch 

 holes every ten inches, thus . ' . " . " . 

 i.e., alternately. The steam is put in at 

 a pressure of thirty to fifty pounds until 

 it rises in a cloud from the bed. 



Third. The pan method, of which a 

 ()icture is shown. This pan is of gal- 

 vanized iron of any convenient size, — 

 say, three feet by nine feet, and six 

 inches deep. This is pressed into the 

 soil about two to three inches. Connec- 

 tion is made by hose to centre of top of 

 pan. The slcam is turned on at thirty 

 pounds for thirty minutes. Where one 



renews the soil each year the soil that is 

 used for potting up can be easily steril- 

 ized in a sort of oven made of wood side 

 with pipes in the bottom, as in num- 

 ber two. 



In all cases, the earth should be fresh- 

 ly dug over and friable in order that the 

 steam may work through it. 



We have done little with chemical 

 sterilizers, the only one we have used 

 being formaldehyde. It gave very sat- 

 isfactory results, but the bed must be left 

 ten to twelve days after application be- 

 fore planting, while with steam it is 

 ready for use in twenty-four hours. 



The greater part of our work has been 

 on tomatoes. We have raised our aver- 

 age per plant by one and a half to two 

 pounds of fruit. In lettuce and cucum- 

 ber, the results have also been very 

 noticeable. At Rothamsted Experiment 

 Station in England, they have had very 

 similar results to ours. A very interest- 

 ing account of their work is given in the 

 Journal of the Board of Agriculture for 

 January, 1913. 



Forcing Rhubarb 



John Gall, Inglewood, Ont. 



A simple means of forcing rhubarb 

 that is specially advantageous after the 

 crops indoors are more or less eshaust- 

 ed is that of raising supplies outdoors 

 by artificial means. This may be done 

 as soon as the worst of the winter is 

 over, and is a practice that should be 

 extremely popular, as anyone with a 

 small amount of trouble may achieve 

 results that are very satisfactory. For 

 successional crops, outdoor forcing is 

 much to be preferred. The plants should 

 be forced where they are growing, and 

 if a warm border is available, so much 

 the better. 



All that need be done in forcing a crop 

 outdoors is to cover the crowns of the 

 plants with barrels, tubs, boxes, or any 

 such article which shall have a mov- 

 able lid. Large barrels should be sawn 

 in two. The top end of the barrel should 

 be knocked out, and made to suit the 

 purpose of a movable lid, this being 

 removed for observation and air-giving, 

 also for obtaining supplies when ready. 

 These utensils should be embedded in 

 stable manure and leaves, this material 

 providing the necessary warmth to ex- 

 cite the crowns into growth. When 

 leaves and stable litter are mixed in th< 

 proportion of about two of the former 

 to one of the latter, a gentle heat may 

 be provided. 



It is surprising how simple and effec- 

 tive is this mode of forcing rhubarb. 

 A splendid crop of luscious stalks may 

 be readily obtained by these means. 



On a soil containing large quantities 

 of lime use superphosphate as a top 

 dressing in the spring and at the rate 

 of 300 to 500 lbs. per acre. 



