SOIL MAKING. 



II 



minous crops as a means of increasing crop production. Unfortunately 

 the method has not hitherto proved a success here ; not on account 

 of any inferiority on the part of our bacteriologists, but because in 

 this country we have no wide stretches of virgin land only recently 

 brought into cultivation, such as can be seen in the United States 

 and in Germany. The subject is worth reopening, however, now that 

 considerable quantities of grass land are being broken up, and in view 

 of this new factor we are looking into the matter at Rothamsted. 



Other methods of controlling the organisms are being attempted, 

 notably by means of partial sterilization. 



The process of soil making is very slow under natural conditions : 

 Nature never hurries. We are watching the process at Rothamsted. 

 A brick chamber has been constructed and it is rilled with subsoil 

 drawn from 12 ft. below the surface. The changes are being observed, 

 but they are very slow. This is also brought out very clearly in the 

 waste mounds of the Black Country in Staffordshire. An enormous 

 area in this region is covered with spoil-heaps containing the refuse 

 from coal-mines, furnace ashes, slags, &c. These were dumped as 

 convenience dictated, and no attempt was made to keep them 

 reasonably levelled, or to cover them with any of the soil that they 

 gradually overspread. For over a century the dumping has con- 

 tinued, and now the heaps extend over many thousand acres of land. 

 In 1S66, however, a great area near Walsall was laid out as a public 

 park, part of it being sown with grass and part being planted with 

 trees. For the grass it was only necessary to pick up the surface, sow 

 the seed, and give a good dressing of road-sweepings ; nothing has 

 been applied since. The trees were planted in pockets of earth, out 

 of which, however, they have long since grown. 



The original material was the shale — locally known as " clunch " — 

 that forms the partings between the coal-seams, and had to be removed 

 in great quantities during the working of the pit. It came out in 

 flaky masses, but it speedily disintegrates to a clay that becomes 

 extremely sticky in wet weather. 



Both the grass and the trees have made satisfactory growth, and 

 the Park is an admirable demonstration of the way in which an un- 

 sightly waste-heap can be converted into a pictuiesque pleasure- 

 ground. Our interest, however, is in the soil changes. The raw 

 mineral matter is gradually undergoing conversion into soil ; but 

 even after thirty years the process is still far from complete. There 

 is as yet no notable difference between the surface and the lower 

 layers, and nothing to mark out the surface-soil from the subsoil. 

 The colour is uniformly greenish-grey, with no break anywhere and 

 no sign of reddening. Chemical tests showed that some oxidation 

 had taken place in the top 9 inches, the ferric iron being 50 per cent, 

 of the total iron, while in the second q inches it was only 40 per cent. 

 There is also more decaying organic matter in the top layer than 

 lower down, and therefore more nitrogen. This will in time lead to 

 the formation of a normal soil, but it has not yet done so. The numbers 



