274 VEGETABLE JORCING Be Ge 8s 
maintain proper physical conditions of the soil, there will 
be as much of the various elements of plant food as the 
crop can utilize. Many of the heaviest crops are grown 
year after year without employing chemicals or any kind 
of commercial fertilizer. Other growers claim that light 
dressings of complete fertilizers have increased yields as 
well as profits. A fairly common practice is to use a little 
nitrate of soda about each plant after the fruit is set. 
Others feed the plants with liquid manure after the fruit 
is set. This method is used in the Kennett Square sec- 
tion of Pennsylvania. Mulching with stable manure, as 
described on page 78, has. practically the same effect. 
Bone meal, wood ashes, tankage and sheep manure are 
often used in the smaller forcing establishments. 
Soil preparation—The general remarks on Soil Prep- 
aration, Chapter V, and Soil Sterilization, Chapter VI, 
apply to the fitting of beds for growing tomatoes. If 
tomatoes only are grown in the houses year after year, 
without any rotation, it will be an advantage to change 
the soil at least every fifth year, though with thorough 
steam sterilization there may be continuous cropping for 
a long term of years. Whenever benches are used, as in 
the Kennett Square district of Pennsylvania, the usual 
plan is to change the soil every year or two. In most of 
the large establishments, containing an acre or more of 
glass, and where ground beds are employed, the common- 
est plan is to apply liberal amounts of manure for lettuce 
during the fall and winter and then to use no manure for 
the tomatoes, which are generally grown as a spring 
crop, except the manure mulch, which is as a rule applied 
after most of the fruit is set. Any soil, however, which 
needs additional plant food or organic matter should be 
enriched by spading or plowing in well-decayed manure 
before the beds are planted with tomatoes. 
In the sections near Philadelphia where mushrooms 
are grown on a large scale it is usual to apply about 4 
inches of manure (see page 424 for composition), which 
