50 VEGETABLE FORCING 



(5) Greenhouse soils should absorb water rapidly 

 without subsequent baking, and the sandy soils are ideal 

 from this standpoint. Their power to retain water is not 

 so great as that of silt or clay, but this is unimportant in 

 the greenhouse, where it is possible to water at any time. 

 A somewhat heavier subsoil, however, with its greater 

 power to hold moisture, is an advantage because it 

 requires less frequent applications of water. 



(6) Interior evaporation is more rapid in sandy soils, 

 and this is thought to be of considerable consequence in 

 relation to oxidation and nitrification, both of which 

 processes are very active in the best greenhouse soils. 



(7) Sandy soils do not bake seriously. This is a great 

 advantage in dispensing with frequent cultivation. In 

 the large forcing establishments many of the sandy soils, 

 which contain a large amount of organic matter, are never 

 stirred or cultivated at any time after the final preparation 

 for planting. 



(8) Sandy soils offer no resistance to root penetration 

 and they encourage the development of the most extensive 

 root system. 



(9) The root crops, such as radishes and beets, are 

 smoother and more uniform in shape, and they develop 

 fewer fibrous roots when grown in sandy soils. 



(10) Walking on the ground, required by harvesting 

 the crops, does not injure the physical properties of sandy 

 soils as is often the case in heavy soils. 



(11) Seed sowing and transplanting are facilitated in 

 sandy soils. 



(12) Apparently it is less difficult to maintain satis- 

 factory sanitary conditions in sandy soils. There are 

 evidences that various diseases appear earlier in heavy 

 soils, from which they seem more difficult to eradicate by 

 any method of soil management or sterilization. 



(13) Sandy soils are easily sterilized. If the soil must 

 be shoveled over and over again, as when steam is used 



