78 HORTUS GRAMINEUS WOBURNENSIS. 



had taken place in the constitution of the soil, in respect of 

 its earthy ingredients : but a very considerable diminution of 

 its decomposino; vegetable and animal matters ; particularly 

 when it is considered how great an addition had been made 

 to the original proportion it contained of this constituent, 

 by the turf, which was incorporated with the soil. 



The finely-divided animal and vegetable matters of soils are 

 so intimately blended with the other constituents, that ma- 

 nure, though applied in sufficient quantity to supply the 

 loss, requires considerable time to bring its parts into that 

 minute state of division, in which it was found in the rich 

 pasture land, on the first examination before mentioned. It 

 is evident the fine divided vegetable matter of the pasture 

 land had been added to it (as it is indeed to all other pasture 

 lands), by manure successively applied to the surface, either 

 by the cattle which grazed upon it, or by top-dressing, and 

 divided and carried into the soil by the action of rain. That 

 this essential ingredient of the fertility of soils is exhausted, 

 even by the growth of the grasses, when the annual supply 

 of manure is suspended, is shown by daily experience ; as in 

 the instance of mowing a pasture for several seasons suc- 

 cessively without any top-dressing, or depasturing with cattle: 

 the produce of grass is found to decrease annually, and if 

 the practice be long continued, it will require nearly as many 

 years, under the best management, to bring the pasture to 

 as productive a state as it was previous to the suspension of 

 its annual supply of surface manure. This likewise shows, 

 that pasture land arrives at a certain degree of productive- 

 ness which it never exceeds, but at the expense of the qua- 

 lity of its produce ; as the surface becomes unequal, the 

 grass rank, of a coarse nature, and less grateful to cattle. 

 In this case (which does sometimes happen), the grass may 

 be brought back to its nutritive state, by stocking the pas- 

 ture sufficiently with different cattle in succession, through- 

 out the season ; the insufficiency of which seems to be the 

 principal cause of the evil. But when such plants as knap- 

 weed (centaurea 7iigra), different species of ragwort, hawk- 

 weed, thistle, and sow-thistle, &c. that are of no value as 

 food for cattle, have established themselves in these pastures. 



