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 nct 
so great as that of silt or clay, but this is unimportant in 
the greenhouse, where it is possible to water at any timc. 
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 
