EARTHS AND SOILS. 45 



fine clay loams, which are friendly to most farm-crops, 

 and most profitable to the owner. 



Clay soils are adapted to the growth of wheat, timothy, 

 oats, and, if possessing a dry bottom, to clover and pota- 

 toes. When intended for a spring crop, it is advantage- 

 ous to plough in the fall, that the frosts may break down 

 and pulverize the surface, and that the vegetable matters 

 turned under may have the better chance to rot in time to 

 benefit the crops. 



There has been recently introduced into Great Britain 

 a new and highly advantageous mode of improving clay 

 lands for tillage, by means of the subsoil plough. Trench 

 ploughing has long been practised, and is analogous, in its 

 effects, to trenching with the spade, as practised in Flem- 

 ish husbandry. In trench ploughing, a second plough 

 follows in the track of the first, and throws a portion of 

 the subsoil to the surface. In subsoil ploughing, no por- 

 tion of the subsoil is brought to the surface, but merely 

 loosened, and pulverized, until, by the admission of air 

 and of water, and by their free circulation through it, it 

 becomes so improved as to possess the fertility of the 

 upper stratum, and is then blended with it. Air and 

 water are charged with highly fertihzing properties ; yet 

 if either remains long stagnant, it loses its fertilizing pro- 

 perties, and becomes prejudicial to vegetable as well as 

 animal health and growth. Trench ploughing mixes the 

 sub with the surface soil, or rather the latter with the 

 former, before the ameliorating influence of air and water 

 has operated upon it, and therefore trench ploughing often 

 proves prejudicial to the first and second crops. But 

 neither trench ploughing nor subsoil ploughing can devel- 

 ope all its advantages upon a stiff clay, with a horizon- 

 tal surface, without the auxiliary aid of what is termed 

 furrow-draining, — of which we shall speak more partic- 

 ularly in our chapter upon draining. The effect of sub- 

 soil ploughing then^ is, to free the soil at all times of an 

 excess of water, to fit it for cultivation, at a much earlier 

 period in the spring, and to increase its fertility. 



The advantages of subsoil ploughing have been partic- 

 ularly illustrated by Robert Laing, Jr., in the Edinburgh 



