212 VEGETABLE FORCING 
for adding other fertilizing materials. In fact, the results 
of hundreds of growers might be cited in support of this 
view. 
It is claimed by some growers, especially by those who 
are cultivating light soils, that the free and continued 
use of stable manure ultimately makes the soil too open 
and porous for the best results with lettuce, and that it 
is preferable to use less manure, and to supplement it with 
commercial fertilizers. This class of growers, however, is 
in the minority, though there are some who obtain ex- 
cellent results from the applications of commercial ferti- 
lizers in connection with manure. Rules cannot be made 
regarding the use of stable manures in greenhouses be- 
cause conditions of soils, supply and kinds of manures 
available, treatment of previous crops, kind of crop to 
follow, etc., are so variable that no one treatment will 
suit all conditions. 
The use of commercial fertilizer in growing lettuce 
under glass was advocated by Thorne of Wooster, Ohio. 
He found that a home mixture of 20 pounds of nitrate of 
soda, 60 pounds acid phosphate and 20 pounds muriate of 
potash, applied .in judicious amounts with moderate 
applications of manure, increased the yields. 
Nitrate of soda is frequently applied to lettuce under 
glass. Sometimes the crop does not make as rapid growth 
as is desired; then a light application of nitrate of soda 
may have a very beneficial effect. As explained before, 
it may be used in liquid form, the plants even being 
sprayed with a dilute solution that will not burn them, 
the solution to be washed from the plants with a spray 
of pure water, 
When nitrate of soda is mixed with the soil before the 
lettuce is planted, one pound to 100 square feet of space 
will be as much as can be used with safety to the plants. 
A practice which is increasing among farmers, and 
there is no reason why it should not be just as valuable 
for greenhouse vegetable growers, is to mix acid phos- 
