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The Cornell Reading-Courses 



In a few places, usually wet and swampy ones, plants have grown up, 

 died, and accumulated with little decay until there are deep deposits of 

 brown or black organic material rich in humus. The rawer deposits are 

 termed peat; the more thoroughly decayed ones are termed muck. The 

 latter, when drained, tilled, and, usually, fertiHzed, are able to produce 

 large yields of some of our most valuable truck crops, such as celery, 

 lettuce, and onions. 



"AJ^'^ 



Fig 9. — Soil formed by water is generally sorted and stratified, as shown in the illustration. 

 The character and arrangement of these strata have large influence on the growth of 

 crops 



SOIL MOISTURE 



Soils hold water in their pores as does a sponge, and this water is taken 

 up by plant roots. Water is necessary as food for the plant, as a regu- 

 lator of its physical condition, and as a carrier from the soil to the plant 

 of other food elements. There must not be too much or too little water 

 in a good farm soil. Some plants require more than others. One class 

 of plants lives in swampy places; another, as the cactus, can live under 

 desert climate conditions. But the great majority of crops prefer 

 a nicely moist condition of the soil, one that holds its form when gently 

 pressed in the hand and that contains only capillary, or film, water 



