ON MANURES. H3 



as by repeated marlings, in large quantities, the surface nf 

 poor ground may be rendered so loose that, in some cases, it 

 has not aflbrded a sufficient hold to the roots of corn and grass. 

 Double the quantity may, however, be laid upon strong cohe- 

 sive soils, for it is not so easy to give them too large a dose; 

 but if cold, wet, or moorish, great circumspection is requisite 

 in the application of this marl, for if the land be not previously 

 well drained, it will only increase its tenacity. 



The earthy marls, if much mixed with clay, are only fit for 

 light soils; and, if applied to them, the quantity must be in- 

 creased in proportion to the deficiency of calcareous matter. 

 When of good quality, containing about 20 to 25 per cent, of 

 calcareous or chalky substance, they are commonly laid upon 

 such land to the thickness of an inch; which will require 135 

 cubic yards, or about 200 single horse cart-loads per acre.* 

 Sandy marl, though generally more calcareous, yet being dug 

 up with less labour, is often used upon clays with greater 

 freedom ; and we have already seen the great extent to which 

 stony marl is sometimes applied.f In many parts, however, 

 where the effects of marl have been extensively experienced, 

 these quantities have been diminished one-half, with nearly, if not 

 entirely, the same immediate effect upon the crops, though its 

 power has been less durable, and has in most cases altogether 

 ceased at the end of at most a dozen years; but then, it admits 

 of the following advantages — a farmer may be able to afford 

 half the expense, when the whole amount may be beyond his 

 means; or, at the same time, he can marl double the extent 

 of land, and he can reap all the probable benefit within the 

 term of a moderate lease. Nor is this all ; for, supposing him 

 to have the freehold — it has been found, that when large 

 quantities of marl have been laid upon the land, though its 

 effects last longer, yet, unless cultivation be carried on with 

 great intelligence and care, these are at length worn out, 

 and by severe cropping to repay tlie expense, large tracts of 

 marled land have been much exhausted. In such cases, too, a 

 second application has been attended with very little benefit; 

 whereas, when it has been laid on in moderate quantites, a 



*Clay marl is not uncommonly laid upon light soils to the extent of two 

 roods, each containing 64 cubic yards ; but on heavy land, half that quantity 

 per acre is considered a good covering. 



1 Throughout many parts of Scotland it is applied at the rate of 200 to 300 

 small cart-loads per Scotch acre, — equal to 160 to 240 per imperial acre. It 

 it is there commonly applied to grass land, and allowed to remain one or 

 more winters on the surface, until completely reduced by the frost. 



