812 



The Weekly Florists* Review* 



time. The tile which were employed for 

 sterilizing were left in the soil, but in 

 these experiments they were not used for 

 suhirrigation purposes. Should the soil, 

 however, be removed and replaced by 

 other soil it would be desirable to remove 

 the tile, which can, however, be easily 

 put back. We have tried many different 

 methods of piping with variations in the 

 pres.sure of steam and we will state that 

 in order to get the cheapest and best re- 

 sults it is necessary to pay attention to 

 two points, namely, that the higher the 

 pressure of steam maintained, the quick- 

 er and more effectual are the results, and 

 the greater the tile area in which the 

 steam has to circulate the quicker it will 

 find its way through the soil and ac- 

 complish the sterilization of the same. 

 It is not only necessary that there 

 should be a number of feet of pipe in the 

 soil in order to successfully heat it, but 

 the area of cross sections is equally im- 

 portant. 



In regard to the cross section area of 

 the pipe we will relate the results of 

 one of our experiments in trying to ster- 

 ilize a bQX of soil with J-inch lead pipe 

 made up into a coil of four lengths. This 

 coil had holes in it 2 inches apart 

 and was placed in a box containing 16 

 cubic feet of earth, which was easily 

 heated in one hour's time when three 

 lengths of 2-inch tile were used and a 

 pressure of 4 or 5 pounds of steam. With 

 the small lead pipe it was found that it 

 was impossible to heat the soil after run- 

 ning it for a number of hours. The 

 method just described is especially 

 adapted to sterilizing soil in the bed 

 where it is subsequently to be used in 

 growing some greenhouse crop subject 

 to nematodes. It should be stated, how- 

 ever, that certain beds are more suitable 

 for this purpose than others. Soil can 

 be more effectually heated in a narrow 

 bed than in a wide one. Many of our 

 cucumber growers raise their plants in a 

 bed 15 or 18 inches wide, 8 to 12 inches 

 deep, and 50 to 100 feet or more in 

 length. Beds approximating these di- 

 mensions could be easily heated in a 

 short time at little expense, and in_ a 

 cucumber house it would be most desir- 

 able to construct them after this manner. 

 Not unfrequently, however, cucumber 

 houses are not provided with benches, 

 but the vines are grown directly in the 

 ground soil. In this case should steriliz- 

 ing becoiin' iMi. -i.iv, Ihf earth in which 

 the phnii- i. ■ ii/ ' :in be separated 

 from the 1 . 11,1 1 II I II : -li liy means of 12- 

 inch boaiil- I 'I I'liiiiK and this lot of 

 earth can be tiled and then treated. The 

 boards or plank arranged in this man- 

 ner restrict the amount of soil to be 

 treated and prevent contamination from 

 the untreated. In case pots are used, 

 as frequently happens in tomato culture, 

 the earth can be sterilized in a special 

 bed or the pots containing the earth can 

 be placed in a tight box and sterilized, al- 

 though this latter method is not so prac- 

 tical, as pots take up more room than 

 soil placed in a bed. 



For sterilizing small quantities of 

 earth we make use of an ordinary small 

 house boiler which heats our laboratory 

 and seldom indicates more than 3 or 4 

 pounds pressure of steam. Tliis is con- 

 nected with a box containing 15 cubic 

 feet of earth, in the bottom of which 

 is b\iried three lengths of tile supplied 

 with steam from the boiler. With a 

 pressure of 3 or 4 pounds of steam the 

 box can be easily heated to 212 degrees 



F. in one hours time and this amount 

 of earth will till about fifty 10-ineh pots. 

 A small bed of this description would 

 be exceedingly convenient for florists in 

 sterilizing earth for such pot plants as 

 cyclamens, etc. 



The method of ridding the soil of nem- 

 atodes where such plants as cucumbers, 

 tomatoes, etc., are sown and where the 

 crop is obtained from the seed offers 

 fewer obstacles than such plants as vio- 

 lets, where transplanting is accomplished 

 by separation, as the latter process ne- 

 cessarily includes taking some of the 

 old soil with the plant. If the violet 

 plants are affected with nematodes it 

 must be clear that the separating and 

 transplanting of the plant into new soil 

 would infest it whether sterilized or not, 

 and result in a crop of sickly plants cov- 

 ered with leaf spots and few flowers. The 

 only method which can be employed at 

 present to control this trouble would be 

 to start cuttings of the violet in steril- 

 ized earth, and when the cuttings were 

 ready to transplant to place them either 

 out of doors in some newly turned up 

 land, or land which had not been con- 

 taminated with nematode infected ma- 

 nure, or else into earth in the green- 

 houses which has previously been steril- 

 ized. 



The manner in which roses are propa- 

 gated also gives rise to similar obstacles 

 in regard to nematode infection. If the 

 same care is taken in regard to con- 

 tamination as in violets the nematode 

 problem is one which need give no alarm. 

 Some rose growers in Massachusetts have 

 never been troubled with nematodes. Mr. 

 Montgomery, who possesses considerable 

 skill, knowledge and experience in rose 

 growing, and who has charge of the ex- 

 tensive Waban conservatory at Natiek, 

 informs us that they have never been 

 troubled with nematodes upon their 

 roses. They make a practice of using 

 soil composted with cow manure, which 

 is allowed to remain out over winter. 

 Tliere is no doubt that owing to this 

 method of preparing the soil they are 

 able to keep nematodes in check. 



Cost of Sterilization. 



The expense of sterilizing the soil will 

 largely depend upon one's equipment 

 and the conditions under which it 

 has to be done. If one has a 

 large steam boiler which he uses 

 for heating his houses, then the nec- 

 essary expenses involved would not be 

 very great. The expense of purchasing 

 tile or steam pipe, -if one happens to use 

 such, whirOi in the Intter instance would 

 have to It ilrillr.l niifl iMiinected, would 

 he the li. .n I. -I t. Ih:ji. We prefer tile 

 to steam |ii|.r and tlijnk 1 liey are fully 

 as etiective, and then, again, they can 

 be used for suhirrigation purposes, a 

 practice which, according to those who 

 have experimented with it, gives bene- 

 ficial results. On the other hand, if one 

 had to purchase a steam boiler, together 

 with the tile, the first expense might he 

 of some account. The 2-inch tile, how- 

 ever, cost about one cent each, or pur- 

 chased in quantities somewhat less, and 

 are slightly over one foot in length, and 

 a secondhand steam boiler of or 8 

 horse-power, giving a pressure of steam 

 equal to 40 or 80 pounds, can he pur- 

 chased for about $50 or $60, and would 

 answer the purpose for most greenhouse 

 growers. I^arger boilers would be better, 

 as they carry more water, a necessary 

 feature in this kind of work, inasmuch 

 as there is considerable water used up 



in heating owing to the condensation of 

 the steam. The soil in a bench 12 inches 

 deep, 15 inches wide and 80 feet long, or, 

 in other words, 100 cubic feet of soil, in 

 which were placed two lengths of tile 

 2 or 3 inches from the bottom, could be 

 easily heated in one and one-half to two 

 hours' time. The tile in such a bed, we 

 will say, costs $1.75, and the extra ex- 

 pense for coal would be unimportant. 

 Some further idea of the expense of heat- 

 ing the soil can be obtained from the 

 amount of soil employed and the time re- * 

 quired to heat it to 212 degrees F., as 

 ascertained by Galloway and others. Ac- 

 cording to Galloway, he succeeded in 

 heating about 72 cubic feet of earth in 

 two hours' time. Lodder's beds evident- 

 ly contained 480 cubic feet of soil, which 

 he heated in three hours, while Rudd's 

 beds contained 600 cubic feet, which he 

 heated in two hours, and, according to 

 Mr. May, he heats 112 cubic feet in one 

 and one-half hours. 



Effects of Heating the Soil on the Growth 

 of the Crop. 



In the numerous crops of cucumbers, 

 tomatoes and lettuce which we have 

 grown in sterilized earth we have never 

 noticed anything of a detrimental na- 

 ture, but, on the other hand, a decidedly 

 beneficial effect as the result of steriliza- 

 tion. Not only is this shown in the dif- 

 ference in color which the plants take 

 on, but in an appreciable acceleration of 

 their growth. We have repeatedly run 

 parallel cultures of sterilized and un- 

 sterilized soil and have invariably 

 noticed these effects on cucumbers and 

 lettuce. It has long been known among 

 practical gardeners that heating the soil 

 produces beneficial results. Every green- 

 house soil contains humus or vegetable 

 mold, and it is recognized by vegetable 

 physiologists that the presence of humus 

 in the soil plays an important part in 

 assimilation and plant growth, but its 

 efficiency depends partly upon the stage 

 of decomposition at which it has arrived. 

 It has been shown by experiments in 

 which plants are treated in one case with 

 humus in the raw condition, and in the 

 other with humus which liad been sub- 

 jected to the action of steam for several 

 hours at a temperature of 212 degrees F., 

 that there is considerable difference in 

 the yield of the crop. It has been found 

 that the same quantity of soil, after the 

 action of heat, yields a crop many times 

 in excess of the former or untreated soil. 

 In other words, by heating we convert 

 the humus compounds in the soil into a 

 more available form for the utilization 

 of the plant. That the heating of the 

 soil gives rise to some changes is shown 

 by iK ilarkn ..il,,r and more porous con- 

 diti-iiaihl ii 1 iiiioMiiliirdlv due to these 

 ehan,^,- ^^1,,,|, !,,im lak.-n' place in the 

 huiiMi- ...iniMiinhl- will,), account for the 

 accelerated and vigorous growth of the 

 plants. Another feature which is char- 

 acteristic of sterilized soils is the un- 

 usual occurrence of humus loving plants, 

 or saprophyds, that grow tipon it, which 

 is a good indication that the organic 

 matter contained in the soil has under- 

 gone changes through the action of the 

 heat. We have ourselves observed more 

 than once certain species of saprophytic 

 fungi growing upon our steamed beds 

 which have never shown any tendency 

 to grow on unbeated soil, although, with 

 the exception of being steamed, the soil 

 was exactly the same as that upon which 

 they never appeared. 



