SOIL PREPARATION 



71 



ing the soil. Furthermore, the grower must not lose 

 sight of the fact that a properly handled greenhouse soil 

 improves in its physical properties from year to year. 

 This is particularly true of the heavier types. 



In greenhouses covering thousands of square feet of 

 land, soil renewal is quite out of the question and rarely 

 practiced. To take out the old soil and bring in the new 

 is an exceedingly expensive operation, the cost far sur- 

 passing that of sterilization. The expense of soil 

 preparation outside of the greenhouse should also be 

 considered before one decides to make frequent renewals. 



Fig. 27. Manure is usually placed in compost piles near the houses. 

 (In this instance, mushroom houses.) 



Composting. In many of the smaller greenhouses 

 there will always be more or less necessity for the chang- 

 ing of soils, and the managers should have a thorough 

 knowledge of the principles and practice of composting. 



Horse manure is almost universally employed in com- 

 posting (Fig. 27), although cow manure is often used for 

 this purpose by florists. To make composting effective, 

 three things must be accomplished : (1) The fiber of the 



