Some Causes of Unproducticcncss in Soils. 125 



ponents preponderates, so as to give the mixture the character 

 of a clay or sandy soil, or to show in too marked degree the 

 properties of lime or organic matter. 



On the other hand, sterility or comparative unproductiveness is 

 often caused by such a preponderance in the soil of one of these. 

 Each of these ingredients of all fertile soils possesses special 

 chemical and physical properties conducive to the development 

 of plants, and it will be readily understood how essential to 

 luxuriance of growth is their intimate and nicely-proportioned 

 mixture, such as we find it in alluvial soils. 



The following Table illustrates the composition of soils which 

 are unproductive on account of the preponderance of one of the 

 four chief materials of all soils : — 



Composition of unproductive Peat-land, Clay, Calcareous and Sandy Soils. 



Xo. 1. No. '2. No. 3. No. 4. 



Calcareous Soil. Santly Soil. Clay Soil. Peaty Soli. 



Moisture 2-65 



Organic matter and water of com-) .^q r.ai 49-(r 



bination j " 



Oxides of iron and alumina .. .. -780 5-93 10-95 10-8S 



Carbonate of lime 73-807 -39 -86 2-29 



Magnesia -825) .. -26 -75 



Potash and soda traces f -28 -39 '90 



Phosphoric acid -242 .. -10 -OG 



Sulphuric acid 1-546 .. -30 1-04 



Silica 16-710) 86-19 



Insoluble siliceous matter (fine clay) 6-090 j .. 79-20 35-01 



100-000 100-00 100-00 100-00 



4. Soils are unproductive to/ien a thin layer rests on the bare rock. 



I am acquainted with several localities Avhere the soil is of 

 excellent quality, but too near to the rock to be productive. We 

 should bear this in mind in discussing the state of agriculture in 

 different counties or districts, as this obstacle will baffle the utmost 

 skill of the agriculturist though he might fertilise the barren 

 sand or reclaim the unhealthy swamp. 



5. Soils are unproductive ichen they rest on impervious or extensive 

 clay subsoils, ivhich are not easily drained efficiently. 



A good deal of clay land. I believe, is unproductive solely 

 because it rests on impervious stiff clay, probably 30 or 40 feet 

 in thickness. Ordinary drainage, I fear, although it improves 

 the character of such clay land to some extent, does not make 

 sufficient impression upon its physical condition. Clay soils of 

 that description occur in the lias formation, where they are known 

 as scouring-land, on account of the tendency of the herbage to 

 scour sheep and cattle. Some time ago I made an analysis of 



