300 GEOLOGICAL SURVEY OE NEW JERSEY. 



is claimed by many that forests do better on soils which have 

 been cultivated for a time. The soil is mellowed by the process 

 of cultivation, and the inorganic materials which have leached 

 through the surface during the process of cultivation are reached 

 by the roots of the trees. Pines which spring up in old 

 abandoned fields are very vigorous, and in Virginia signs of the 

 old corn-rows may be seen in forests on land which produced 

 cotton and corn up to the time of the Civil War. At the same 

 time the materials which have escaped the field crop by leaching 

 are brought again to the surface by the tree so that the soil is 

 being rendered fit again for agricultural purposes. The forest 

 is thus an important factor in the rotation of crops, as I have 

 already explained in the first chapter in connection with the 

 eastern shore of Virginia. Although the farmers in that region 

 remove the litter, they wisely allow old fields to come again in 

 pines and clear fresh pine forest. By making the rotation of 

 the pine short, the growing of pines in the sand-lands of the 

 South may in time play an important agricultural role, and may, 

 as one in the series of several crops, be necessary to maintain 

 the productiveness of the soil. 



It must not be forgotten also that the roots of trees corrode 

 even the silicates, and coarse sandy soil, under the influence of 

 vegetation, becomes gradually loam-like in nature, although 

 clay may be lacking. Eor this purpose pines have great advan- 

 tages in that they are adapted to sandy soils and that the stumps 

 soon rot after the tree is cut. It is not a difficult task to clear 

 a pine forest for agricultural purposes. In planting old fields 

 the surface should be plowed under in order to bring fresh soil 

 to the top. The young crop demands a rich surface-soil ; later, 

 when the roots penetrate into the subsoil upon which the tree 

 feeds, it can take care of itself. Smets recommends, therefore, 

 the growing of young plants in nurseries in good soil first, and 

 claims that the so-called hardening of plants by growing them 

 under adverse conditions is a mistake. This is, of course, expen- 

 sive, and is not necessary in a country where a good crop is 

 usually produced naturally or may be easily produced by sowing. 



There is formed in the heathlands of the Campine a peculiar 

 powdery dry light-brown or black humus which decomposes 

 with difficulty and collects in thick beds. It is formed mainly 



