124 So)nc Cai/scs of Unproductireness in Soils. 



for this reason many cannot be made fertile by the application of 

 manures which, like lime, supply only one material. Sandy soils, 

 more especially, often stand as much in need of lime as of phos- 

 phoric acid or of potash. Tlieir general deficiency in all these 

 important elements of fertility is clearly seen in the following 

 analysis, showing the 



Composition of a Poor Sandi/ Soil. 



Moisture 4"78 



Organic matter .. .. 1'03 



Oxides of ifoii and alumina 1'72 



Lime -19 



Magnesia "10 



Potasli -23 



Soda none 



Pliosphoric acid "04 



Sulphuric acid '12 



Carbonic acid and chlorine traces 



Insoluble siliceous matter '.)1,T'J 



Consisting of: 



Siiicii 89-32 



Alumina TSl 



Lime none 



!Nragnesia 'Sfi 



Potash -L"* 



Soda -15 



100-00 

 It will be seen at a glance that tliis is a hungry soil, which 

 requires lime as well as phosphoric acid and alkalies. As long 

 as we do not possess a cheap source of potash, well made yard- 

 dung, liberally applied, seems to be our only generally available 

 resource for maintaining or increasing the productiveness of 

 soils as poor and defective as this. It is upon soils of that 

 character that town-sewage produces the best economical result, 

 when applied in large quantities. 



We have seen in this section that soils often are unproductive 

 because they are deficient 



a. In lime. 



b. In phosphoric acid. 



c. In potash, or, 



d. In two or more of these important ash-constituents of 



plants. 



3. Soils are barren or unproductive token they contain a large pre- 

 ponderance of organic matter, or of .mnd, livie, or even of pure 

 clay. 



The most fertile soils, such as alluvial-deposit or warp land, 

 may be regarded as intimate mechanical mixtures of clay, lime, 

 sand, and organic matter, in which no one of these essential com- 



