THE SOILS OF THE NORTH-EAST OF SCOTLAND 85 
crops grown in the district—oats, turnips, potatoes and grass—are those 
which are suited to soils of moderate acidity. Barley and sugar beet 
are not so well adapted to the district and can be grown successfully 
only on soils of low acidity or on those which have been well limed. 
It is characteristic of the soils of this area, and especially of those 
derived from granite and other crystalline rocks, that they contain felspars, 
mica and other crystalline minerals often in a very fine state of division, 
which are either unweathered or in a very imperfectly weathered condition. 
These silicates contain large stores of potash, lime, soda and magnesia, 
and the presence of these supplies of bases combined in insoluble silicates 
helps to maintain the fertility and condition of the soil by gradually yielding 
up bases during weathering, which not only supply food directly to 
crops, but by neutralising acids prevent the soil becoming more acid 
than it is. Such soils often contain considerable supplies of phosphate 
also, derived’ originally from the presence of apatite in the crystalline 
rocks from which they have been formed. These soils, formed from 
crystalline igneous and metamorphic rocks, are often of high natural 
fertility, especially when well drained, for they contain a good supply of 
potash, lime and other bases, and are also naturally well supplied with 
phosphoric acid. As shown below, they are also generally well supplied 
with humus and nitrogen. Though in many cases they have not been 
limed for long periods, or have received very little lime, they are not so 
acid as might be expected. For the same reason, even when they show 
considerable acidity, applications of lime often produce little effect, for 
they are already well supplied with lime and other bases in the form of 
compound silicates which are sufficiently reactive to supply bases for most 
of the needs of the soil. 
As the surface of the country, before it was reclaimed, was largely 
covered by moorland and peat the soils are generally well supplied with 
organic matter and contain a fair supply of nitrogen. The minerals 
forming the soil generally contain iron, often in considerable amount, 
and the formation of iron pan, due to the solution of iron in the presence 
of organic matter and its redeposition lower down, where it binds 
together other materials, is very common. ‘The presence of such a pan 
from a few inches to a foot or two below the surface often interferes 
seriously with the fertility and value of the soil by preventing drainage 
and aeration and by limiting the depth to which plant roots can penetrate. 
When the pan can be broken up, the fertility of the soil is often con- 
siderably improved. 
