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 
