6 MASS. EXPERIMENT STATION BULLETIN .S80 



peaty humus layer of considerable depth frequenth accumulates. 



A moderately high rainfall has subjected all soil layers including the humus 

 layer to a strong washing or leaching action, which has the effect of removing 

 material both chemically and physicall)' from the surface soil layers. Some of 

 this material may be redeposited at lower levels in the B-horizon,and some may 

 pass on through the profile and be lost altogether in the drainage waters. Fre- 

 quently chemical action is particularly strong in the A-horizon. Practically all 

 readily soluble salts are carried away, together with a considerable proportion 

 of the bases, including calcium, magnesium, potassium, and sodium. These 

 bases, according to Robinson, "in the completely leached profiles of humid 

 climate . . . are lost in the drainage; the profile falls in base-status and becomes 

 acid until the loss in bases is just balanced b\' gains from the weathering of minerals 

 in the soil."' The same author goes on to say: 



When the base-status of the soil is lowered by leaching out of bases, the 

 cla>' complex ma\' undergo decomposition. In the initial stages, this may 

 result simply in the liberation of free silicic acid, alumina, and ferric 

 oxide, such a change being betokened by the yellowish, orange, or brown 

 color of hydrated ferric oxide. Where the removal of bases is more ac- 

 centuated, ferric oxide, and in extreme cases, alumina, may pass into 

 solution associated with humic acids, and be removed from the upper 

 horizons, which thereby acquire a bleached appearance. Deposition of 

 ferric oxide and alumina occurs at lower levels, giving a yellowish-brown 

 sequioxide B-horizon, which in extreme cases may be hardened to a pan. 



The presence of a well-defined bleached A2-layer and a well-developed pan 

 formation or "orterde" is characteristic of a number of important soil types in 

 Massachusetts. The soil profile which develops under such circumstances is 

 known as a "podzolized" profile and the process itself as "podzolization." It is 

 characteristic of a great group of soils known as podzols or as podzolic soils. 



Practically all soil types in Massachusetts are podzolic in nature. It is not 

 difficult to understand, therefore, why the profiles of almost all soil types are 

 quite similar in their chemical characteristics. There are, of course, marked 

 variations between the profile characteristics of different soil types, but these 

 variations are due primarily to the diversity of the parent soil material and to 

 differences in the extent to which the process of podzolization has taken place. 



Brown Podzolic Soils 



A majority of the soil types belong to a subgroup known as "brown podzolic 

 soils" or "brown forest soils." They have been characterized as imperfectly 

 developed podzols "having, in timbered areas, an organic mat on the surface and 

 a very thin gray leached [or bleached] horizon just below it — usually less than 

 an inch thick. The B-horizon is largely yellowish brown in color and has only 

 the beginnings of a dark-brown orterde just below the gray A-horizon. "* Some 

 of the agriculturally important soil series belonging to this group are the Glouces- 

 ter, Plymouth, Charlton, Paxton, Wethersfield, and Cheshire series. 



Podzols 



In the eastern part of the State where the parent materials contain a high 

 proportion of quartz sand and where the vegetation was largely coniferous, and 

 also in the western highlands where the climate is cooler, groups of soils are found 

 which are more completely podzolized and are classified as true podzols. The 

 A-horizon is more intensely leached, the bleached layer thicker and more clearly 

 defined, and the pan formation or orterde more fully developed. The less agri- 

 culturally important soils of the Berkshire, Worthington, Becket, Hermon, 

 Hinckley, and Duke series are all included in this group. 



■'Mother Earth, p. 66. 



^Soils and Men, U. S. Dept. Agric. Yearbook (1938), p. 1029. 



