602 Journal of Agriculture, Victoria. [10 Oct., 1916. 



FALL TEEATMENT OF SOILS FOR PLANT BEDS PRACTICABLE. 



In spring the soil is liable to be full of water^ and better conditions for bed 

 spading and preparation may occur in late fall, besides avoiding the delay in 

 seeding which is often objectionable in spring treatment. When fall treatment 

 is practised it will not be necessary to re-spade the bed in spring, preparatory 

 to seeding; only the surface need be .worked. The object of such treatment is 

 to destroy the forms of the root-rot fungus or other species, such as bed-rot, 

 &c., which otherwise live over in the beds where the disease occurred in 1915. 

 Because the " Thielavia " is found upon numerous other host plants it is not 

 clear that new bed locations will avoid the necessity for treating the soil. For 

 the present it is not expected to discuss and list the plants attacked ; rather 

 to prepare a method whereby healthy tobacco plants may be produced for 

 setting in the field. 



PREPARATION OF SOIL TO BE TREATED. 



Previous to treatment by any method, the soil should be prepared much 

 after the manner of preparation for seed-sowing. If manure is to be applied to 

 the bed area, make such application in advance. When chemical fertilizers are 

 to be used, their application need, not be made until spring, just before sowing 

 seed. The soil to be treated is taken in good workable condition, certainly 

 not ovjer-wet, spaded to the necessary depth, and thus handled in a preparatory 

 manner. Very dry soils have not been found satisfactory. There seems to be 

 no need to rake over the spaded soil beyond that necessary to fine it enough to 

 facilitate penetration of the drench or steam. 



STEAM STERILIZATION BY INVERTED PAN. 



The apparatus necessary for steaming consists of an inverted pan made of 

 galvanized iron, having nipple attached for steam hose, which is to connect 

 the pan with a boiler of 8 to 12 H.P. capacity; the ordinary traction engine 

 has proved serviceable in furnishing steam. A pan which will fit the usual plant 

 bed, namely, 5 ft. 6 in. by 8 ft. 6 in. by 7 in. deep, is advised. This is to be 

 made of heavy galvanized sheet iron, preferably rust-proof, of 18, 20, or 22 gauge. 

 These metal sheets, ranging in size from 2 to 3 feet wide by 8 to 10 feet long, 

 are seamed, riveted, and braced by strap and angle iron for stiffening the pan. 

 Four or five sheets will be necessary. 



After the soil is prepared the pan is inverted over a part of the bed, with 

 edges pressed down into the soil so as to form a steam-tight air chamber. 

 Steam is then turned on from the generating boiler under 50 lbs. to 80 lbs. 

 boiler pressure. At this pressure it will sometimes be found necessary to 

 weight down the pan to keep it from lifting. Each area requires to be steamed 

 approximately one hour. After removing the pan to adjacent part of bed, the 

 soil is to be tested with a thermometer, and should register 180 to 210 deg. F. 

 at a depth of 3 to 6 inches. If this temperature has not been attained, increase 

 the steaming period by 10 to 15 minutes. 



BED DRENCHING WITH FORMALDEHYDE. 



It is more convenient to drench the soil of the plant beds with a solution 

 of formaldehyde (formalin), as only a sprinkling pot with hose will be required 

 in addition to the chemical. However, previous experience fails to show equal 

 effectiveness in complete killing out of the plant-bed fungi. 



The strength of solution to be most successful probably should be stronger 

 than that heretofore suggested, and the amount of solution applied may prove 

 to be less with the stronger formula. The proi^ortion of one gallon of 



formaldehyde to 50 gallons of water, and the ajiplication of one-half gallon per 

 square foot of surface, has been suggested by Johnson in treatment of plant 

 beds for a different fungus " Pythium." This may prove to be successful for the 

 root-rot. For the present a strength of one gallon of formaldehyde to 100 

 gallons of water is promising. Of this weaker solution the total application 

 should amount to three-fourths of a gallon to one gallon per square foot covered. 

 In the application, the solution should be applied as evenly as possible to avoid 

 waste, and at two or more applications. In all cases, effectiveness is gained by 

 covering the plant-beds with canvas to prevent escape of fumes. Before appl}dng 

 the solution, the beds should be fairly moist and friable. If locally too dry an 

 unevenness will show in the results of treatment. Even penetration of all the soil 

 is the aim. 



