126 Some Causes of Unproductiveness in Soils. 



notoriously bad land from Shepton-Mallet, Somersetshire. The 

 soil contained in 100 parts : — 



Moisture 4-54 



Organic matter aud water of combiuatiou 14-40 



Oxides of iron and ahimina and phosplioric acid .. 14*45 



Sulphate of lime '26 



Carbonate of lime 14'80 



Magnesia '9(5 



Totash and soda "93 



Insoluble siliceous matter (cliidly clay) 49'GG 



100-00 



This soil had rather a dark colour which was due partly to 

 protoxide of iron, partly to the large proportion of organic matter, 

 which enters into its composition. Although not injurious in 

 itself, an excess of organic matter, as well as of protoxide of iron, 

 indicates a condition of the land which is unfavourable to the 

 healthy growth of plants. In a porous, well-cultivated soil, freely 

 penetrated bv the atmosphere, the accumulation of organic matter 

 never becomes excessive, nor does such a soil contain much 

 protoxide of iron. The presence of the latter in considerable 

 proportions always shows that the soil is not sufficiently aerated 

 to produce a healthy and nutritious herbage. 



Chemically considered this soil contains an abundance of all 

 the mineral elements which enter into the composition of the 

 ashes of plants, and it is found in practice that farmyard-manure 

 does not produce any marked effect upon it, which shows plainly 

 that it is not the want of plant-food that renders it unproductive. 

 These lias lands rest upon a clay bed of great depth which 

 approaches very near to the surface. 



In many instances, therefore, under-drainage, besides taking off 

 the surface water, produces little alteration in the condition of 

 the surface soil, for the simple reason that it is too thin, and the 

 clay sub-soil bed too tenacious and too deep to be penetrated 

 to any extent by the ameliorating influence of the atmosphere. 

 These tenacious soils are consequently damaged by excess of water 

 and coldness, which retard vegetation and make it very gradual 

 during the early months of the year. 



5. Soils are unproductive when the Drainage is defective. 

 Under this head 1 need not offer any observations, for it is 

 now perfectly well known that bad drainage is a frequent source 

 of sterility in land, which has only to be thoroughly drained in 

 order to become permanently improved. 



6. Soils are unproductive ichen their pliysical characters are had. 

 An actual case lately brought under my notice will best 



