SOILS 51 



in pipes, the sandy soils are handled with the greatest 

 ease. There is always danger of injuring the physical 

 properties of heavy soils when either steam or formalin is 

 used for sterilization. 



(14) Sandy soils have a wider adaptation to greenhouse 

 vegetables than do the heavier types. 



So important is sand in greenhouse soils that it is often 

 transported long distances and mixed with the heavier 

 soils that must be used. The financial returns from 

 greenhouse crops probably justify the practice ; and yet it 

 is better to select soils, if possible, which make this 

 expenditure unnecessary. There is an increased tendency 

 to mix muck with various types of soils to be used for the 

 forcing of vegetables. This practice deserves considera- 

 tion wherever a supply of muck is easily available. Both 

 light and heavy soils seem to be improved by its addition. 



Although special emphasis has been given to the im- 

 portance of coarse-grained soils, there are numerous 

 examples of success on heavy types. When a first-class 

 market is easily accessible, no one should hesitate to 

 engage in vegetable forcing simply because a light soil is 

 not available. 



Structure. This term applies to the arrangement of the 

 mineral matter of the soil. In some instances, as in fine 

 silts, the particles are in such intimate contact that the 

 soils are very compact; they form a mass that is not 

 easily penetrated by roots. This condition is most un- 

 satisfactory to aeration, surface evaporation, tillage, soil 

 sterilization, seed sowing and transplanting. Soils of un- 

 favorable structure for vegetable forcing can be greatly 

 modified by proper cultural methods. Tillage may be the 

 means of breaking up the soil into granular masses, and 

 lime may cause the particles to flocculate, while the fiber 

 of stable manures separates the soil into small masses. 

 It is important, however, to avoid if possible the selection 

 of soils of compact structure for the forcing of vegetables. 



