KINDS OF SOILS— THEIR CHARACTERISTICS 53 



loam, which we have learned is intermediate between sand 

 and clay. Wet all of them equally. Place the boxes in the 

 free air or sun and allow them to dry. Which soil loses its 

 moisture first? Which last? 



Peat or vegetable matter makes up a large part of some 

 soils, particularly in low places. The vegetable matter may 

 be more or less decayed, and is often called peat. It is found 

 in bogs and marshes and other wet places. When the peat 

 has nearly all decomposed it is called muck. If peat and muck 

 soils are well drained and are supplied with enough hme, they 

 are very productive. They are often used for such market- 

 garden crops as cabbage, onions, celery, and cauliflower. 



Humus. — Partly decayed vegetable matter in soil is called 

 humus. It has a blackish color. In newly cleared farm soil 

 it is derived from the dead roots and leaves of a former vege- 

 tation. Leaf mould found in forests is largely humus. On 

 farms it is secured by plowing under waste materials such as 

 weeds, stubble, roots, vines, and leaves. Farm manure is 

 valuable for this purpose. Special crops are often grown to 

 be plowed under, and when so used are called green manure. 

 When these rot in the soil, humus is formed. 



Humus is very useful in all soils. It improves a sandy 

 soil because it increases its power to take and hold moisture, 

 supplies it with plant-food, and thus increases its productiv- 

 ity. It will absorb and retain more moisture than any other 

 part of the soil. It improves clay soil by loosening it, thus 

 helping the circulation of air and moisture. It is less likely 

 to clod and crust. Humus is the main immediate source of 

 nitrogen, so necessary in the growth of all farm crops. In 

 the formation of humus other plant-foods are set free, — but 

 best of all is its improvement of the structure or texture of 

 the soil, resulting in better drainage, better ventilation, and 

 deeper root growth. 



Lime in Soil. — ^When lime is found in soil it is usually in 

 the form of particles of limestone or marble, but it may be 



