52 MANAGEMENT OF THE FORCING-HOUSE. 
changed rarely long remain free of serious insect or fun- 
gous invasions ; and.in selecting soils for houses, it is of 
the utmost importance to avoid bringing in grubs, cut- 
worms, wire-worms, tomato rust, and the like. It is per- 
fectly possible to add plant food to the old soil, but it is 
impossible to restore its texture by that means, and the 
physical texture is usually more important than its actual 
store of food. In the forcing of lettuce upon ground 
beds, it is not always essential to remove the earth every 
“year, although an inch or two of the top must be re- 
moved if the mildew Has been serious, and the soil should 
always be fertilized before another season of forcing is 
begun. The best growers prefer, however, to replace 
four or five inches of the top soil every summer. 
THE QUESTION OF FERTILIZERS. 
Most forcing-house crops need to be fertilized as they 
grow. This is particularly important for tomatoes, cucum- 
bers and melons. The fertilizer most liked by gardeners 
is liquid manure. This is made from old unleached cow 
manure (such as has been lying for some months ina barn 
basement). A bushel of it is placed ina half-barrel or tub 
and the receptacle is filled with water. After standing two 
or three days, being stirred occasionally in the meantime, 
the liquid is ready for use. This liquid must be reduced 
before it is applied to soil in which plants are growing, and 
the amount of reduction to give it can be determined only 
by experience. Ordinarily, one quart of liquid made as 
here directed will be sufficient for a gallon of the diluted 
material ; that is, one quart of the manure water is added 
to three quarts of clear water. If the manure is strong, 
the tub may be filled with water three or four times before 
the strength of the material is dissolved out. A tub of this 
manure liquid should always be accessible in forcing-house 
work. How often the liquid shall be applied to the crops 
must be determined for each particular case. If the soil is 
