274 VEGETABLE FORCING 



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 



