SOIL PREPARATION 77 



to become very dry. In general farming, drought is 

 thought by some to have a beneficial effect upon the soil, 

 or at least upon the following crop, but it is possible that 

 this is due largely to the absence of leaching and the 

 small draft upon the food supply of the soil when there 

 is a marked deficiency in the supply of capillary water. 

 Though drying may be an advantage to soils out of 

 doors, there is evidence that it is a great disadvantage in 

 the management of greenhouse soils, except for the 

 destruction of nematode worms. 



Stone, of the Massachusetts station, made the follow- 

 ing report in 1902 : "The practice of desiccation or dry- 

 ing greenhouse soil by the aid of the heat of the summer 

 sun has been in vogue with us for some time, for the 

 purpose of observing what effect such treatment would 

 have on certain organisms. We have already shown that 

 the sclerotina or the drop fungus when dried is greatly 

 accelerated in its activity, which increases to a great 

 extent the amount of infection in the succeeding crop of 

 lettuce." 



In this connection Stone further reported as follows in 

 Bulletin 69 of the Hatch station : "In this test the house 

 was closed during the greater part of August, September 

 and October, at which time the soil was subjected to the 

 intense rays of the sun, which heated the soil up to a 

 temperature of 123 degrees, and the air thermometer 

 registered 140 degrees. As the top layer of the soil be- 

 came dry a lower layer to the depth of a foot was forked 

 over two or three times, so that practically the whole 

 amount of soil became desiccated. The results of drying 

 out the soil in one bed containing 308 plants was that 235, 

 or 76 per cent, were subject to drop, and 66, or 21 per 

 cent, to Rhizoctonia. The number of plants which suc- 

 cumbed to the two diseases was 301 out of a total of 308, 

 or 97 per cent. The other half of the house, containing 



