22 SOILS AND FERTILIZERS 



Many muck soils are underlaid by deposits containing 

 lime derived from shells of aquatic organisms that inhabited 

 the bodies of water in which the muck was formed. This 

 adds materially to the value of the land, as lime is a valuable 

 soil amendment, particularly on muck land. It is well to 

 keep this in mind when examining muck land. 



The percentage of potash is much lower than in any other 

 kind of soils, and a potash fertilizer is usually of great benefit 

 to crops planted on muck. 



21. Colluvial soils. — On all steep slopes there is a gradual 

 downward creep of soil particles due to the effect of gravity 

 assisted by rainfall, freezing and thawing, the movements 

 of animals, in fact any agency that starts the particles in 

 motion, after which their direction is almost invariably 

 downward. This soil formation is not extensive, nor in any 

 sense important. Such soils are confined largely to the 

 bases of mountains. They are usually shallow and stony. 



22. Alluvial, soils. — A stream flowing through its valley 

 will erode its bed if very steep and will deposit sediment 

 if nearly level, but under most circumstances it both erodes 

 and deposits soil. As the upper reaches of a river are usually 

 of steeper grade than the lower, it often happens that con- 

 siderable material is picked up by the stream near its source, 

 and as the current becomes slower farther down, this material 

 is deposited. Alluvial soil is, therefore, found most largely 

 along rather slowly flowing streams. 



It is estimated that water flowing at the rate of three 

 inches a second will carry only fine clay, but if this rate is 

 increased to twenty-four inches a second, pebbles the size 

 of an egg will be moved along the stream bed. 



It is quite customary for streams flowing through a flat 

 region both to erode and deposit soil. Such streams are 

 likely to be sinuous in their course, the curves gradually 

 becoming more angular as the current erodes the soil from 



