EXPERIMENT STATION BULLETINS. 433 



development of the eggs of certain free-living nematodes. The re- 

 sults of the above-mentioned workers, together with those obtained by the 

 writer with the eggs of the parasitic nematode, Heterodera radicicola, in- 

 dicate that further work along this line may establish the fact that the 

 other parasitic nematodes will be able to survive soil treatments with 

 chemicals for the same reason, namely, that the egg stage in the life cycle 

 is resistant to the chemicals. 



DATA ON STEAM STERILIZATION OP SOIL. 



During the summer of 1913 it had been intended to conduct experi- 

 ments on the control of the root-knot nematode by steam sterilization, 

 but it was impossible to get a steam boiler for a sufficient length of time 

 to prepare complete experiments. The writer did succeed in getting a 

 boiler for one day, and so was able to collect some data relative to the 

 depth to which the soil could be heated in a given length of time with 

 equipment such as he had. The method and results of this work as 

 given below, will give an idea of the value of steam, but these results 

 are not sufficient to serve as a basis for definite recommendations. A 

 pan ten feet six inches long, three feet wide, and six inches deep, was 

 used in this work. Steam was furnished by a ten horsepower boiler 

 kept at a pressure of seventy pounds. The soil to be treated was first 

 thoroughly spaded up to loosen it to facilitate the penetration of the 

 steam. 



In order to get data on the depth to which the steam penetrated, po- 

 tatoes were placed in the soil at three places, viz., at the end of the pan 

 where the steam entered, at the opposite end, and at the middle. Holes 

 eighteen inches deep were dug and stakes set in them to mark the loca- 

 tion of the potatoes. One potato was placed at the bottom of each hole, 

 eighteen inches below the surface, and the soil was shoveled in until 

 the holes were twelve inches deep. At this depth potatoes were placed in 

 each hole and soil shoveled in until the holes were six inches deep. Po- 

 tatoes w^ere placed in each hole at this depth, and then the holes were 

 filled until they were but three inches deep. Potatoes were placed at 

 this depth and the holes were then filled up until the soil was level over 

 the whole plot. The pan was then connected up with the boiler and the 

 steam turned on. In about fifteen minutes the steam began to lift the 

 pan out of the soil so that steam escaped from under its edges. To 

 avoid this loss of steam, the pan was weighted down with scrap iron. After 

 thirty minutes of treatment the steam was shut off and the pan removed 

 from the soil. The potatoes in the hole farthest from where the steam 

 entered the pan, were dug first. The potatoes at three inches, six 

 inches, and twelve inches below the surface were well cooked through- 

 out and the one at eighteen inches below the surface was very hot. Next, 

 the potatoes in the middle of the plot were dug up, and all found to be 

 well cooked, even the one eighteen inches below the surface. It was 

 next attempted to dig the potatoes at the end of the plot 

 where the steam entered, but the steam had gouged out such 

 a hole in the soil that it was impossible to locate all of them. The two 

 that were found were well cooked. The soil treated is a very fertile clay 

 loam, with a stiff clay subsoil at about twenty-four inches below the 

 surface. 



55 



