616 WHY OLD PASTURES CONTINUE RICH. 



dung will be enriched by all those other fertilizing constituents present in 

 the oil-cake which are not required or worked up by the fattening aniipal. 



Hence it is that the dung of fattening stock is usually richer than that 

 of stock of other kinds. Oil-cake would be a rich manure were it put 

 into the soil at once; it is not surprising, therefore, that after it has 

 parted with a portion of its oil it should still add much to the richness of 

 common dung. 



A knowledge of the kind of material, so to speak, which the animal 

 requires to fatten it, explains in a considerable degree another practical 

 fact of some consequence through which it is not easy at first sight to see 

 one's way. There are in various parts of the island certain old pastures 

 which, from time immemorial, have been celebrated for their fattening 

 qualities. Full-grown stock are turned upon them year after year in the 

 lean state, and after a few months are driven off again fat and plump and 

 fit for the butcher. This, T have been told when on the spot, has gone 

 on time out of mind, and yet the land, though no manure is artificially 

 added, never becomes less -valuable or the pasture less rich. Hence the 

 practical man concludes that the addition of manure to the soil is un- 

 necessary, if the produce be eaten off by stock — that the droppings of 

 the animals which are fed upon the land are alone sufficient to maintain 

 its fertility. 



But the reason of this continued richness of such old pastures is 

 chiefly this — that the cattle, when put upon them, are usually full-grown 

 —they have already obtained their full supply of bone and nearly as 

 much muscle as they require. While on the fields they chiefly select 

 fat from the grasses they eat, returning to the soil the phosphates, saline 

 substances, and most of the nitrogen which the grasses contain. Their 

 bodies are no doubt constantly fed or renewed by new portions of these 

 substances extracted from the food they eat, but they return to the soil an 

 equal quantity from the daily waste of their own bodies — and thus are 

 indebted to, and carry off the land, little more than the fat in which 

 they are observed daily to increase. 



But as the materials of the fat may be, and no doubt originally are, 

 derived wholly — perhaps indirectly, yet wholly — from the atmosphere, 

 the land is robbed of nothing in order to supply it, and thus may con- 

 tinue for many generations to exhibit an equal degree of fertility. 



I give this only as a general explanation, by which the difficulty 

 m.ay be solved, where no other more likely explanation can be found 

 in the local circumstances of the spot, or of the district in which such 

 rich old pastures exist. 



c. The growing animaU again, does not return to the soil all it re- 

 ceives. It not only discharges carbon from its lungs, but it also extracts 

 phosphates from its food to increase the size of its bones, gluten to swell 

 out its muscles, and saline substances to mingle with the growing bulk 

 of its blood. The dung of the growing animal, therefore, will not be so 

 rich as that of the full-grown animal fed upon the same kind and quan- 

 tity of food. Hence from the fold-yard, where young stock are reared, 

 the manure will not be so fertilizing, weight for weight, as from a yard 

 in which full-grown or fattening animals only are fed. 



d. The milk cow exhausts still further the food it eats. In the lean 



