196 071 Permanent and Temporary Meadows and Pastures. 
dense, and the rain or water of irrigation penetrates with greater 
difficulty. During the droughts of summer, the moisture rises 
up less easily from the subsoil ; and thus, from physical causes, 
the production settles down to a normal level. In time, the 
chemical condition of the land also undergoes a material change ; 
not only is the layer of soil which is occupied by the roots 
rendered incapable of supplying a sufficiently large amount of 
the elements necessary to the vegetation, but, owing to the 
continued accumulation of vegetable debris, the layer of soil 
in which the roots live at length becomes sour, even where the 
earth may originally have been calcareous, and may still be 
so in the underlying layers, so that the good plants tend to 
disappear, and give place to a vegetation which is charac- 
teristic of sour land. Moreover, the essential elements, which 
the soil originally contained in sufficient quantities, gradually 
become exhausted ; first by the removal of the crops, and 
secondly from the superabundance of organic matters, by means 
of which the potash, phosphates, and carbonate of lime are 
rendered much more soluble, and are consequently more easily 
carried down into the subsoil, where the roots cannot reach 
them. 
With the exception of the variations due to farmyard or 
chemical manures which may have been recently applied, it 
is practically established by the analyses of the subsoils of grass- 
lands that they are usually richer in phosphoric acid, potash, 
lime, and magnesia, than the upper soil, which is usually 
much richer in nitrogen. This descent in the soil of mineral 
substances by means of organic solvents is rendered very evident 
by the percentage of nitrogen in the subsoil, which though in 
general less than on the surface, yet is often found to exceed that 
of good arable soils. 
Here are some examples taken in cases where analyses of the 
subsoils were made : — 
No. of the 
Analysis 
in General Table 
of Soils. 
Nitrogen in Upper Layer, 
7-874 in. deep 
( = 20 centimetres). 
Nitrogen in Under Layer, 
7 "874 in. deep 
( = 20 centimetres). 
Id 100 parts. 
In 1 Acre. 
In 100 parts. 
In 1 Acre. 
10 
•275 
4-38 tons 
•075 
1-19 tons 
16 
•529 
8-42 ,, 
•511 ■ 
813 ,, 
18 
525 
8-36 
•362 
5-76 
35 
•246 
3-91 
•162 
2-58 ,, 
25 
•3i9 
6-o:? ., 
•123 
1^95 ,, 
