106 CALCAREOUS MANURES— PRACTICE. 



has been deprived, by washing, of a considerable portion of its natural 

 soil, though not yet made entirely barren. The foregoing remarks equally 

 apply to this kind of land, to the extent that its soil has been carried off. 

 It will be profitable to apply marl to such land ; but its effect will be dimi- 

 nished, in proportion to the previous removal of the soil. Calcareous soils, 

 from the difference of texture, are much less apt to wash than other kinds. 

 Within a few years after marling a field that has been injured by washing, 

 many of the old gulleys will begin to produce vegetation, and show that a 

 soil is gradually forming from the dead vegetables brought there by winds 

 and rains, although no means had been used to aid this operation. 



This newly acquired ability to resist the washing power of rains, is one 

 of the most beneficial effects of marling on hilly lands. And this effect is 

 no less certain, than it is conformable to the theory of the action of marl 

 and to reason. On soils containing very little lime, (or none, as in naked 

 sub-soils,) whether they be sandy or clayey, there is nothing to combine the 

 vegetable matter with the soil, nor the different ingredients of the soil wiih 

 each other. Consequently they have no cohesion, and whenever made very 

 soft, or semi-fluid by rains, and there is any declivity, there is nothing to 

 prevent the soil, or upper surface, being washed off by excessive rain, though 

 falling gently. Of course, torrents of rain produce the same injurious effects 

 much more rapidly and effectually. But when such soils have been made 

 calcareous, a chemical combination and bond of union and coherence is 

 formed between the lime and the putrescent or organic matter, and of both 

 with the silicious and argillaceous parts of the soil, which combination is 

 able to resist any but an unusual degree of the washing action of rains. 

 Moreover, by the increase of productive power thus given, grass grows 

 more kindly and rapidly, and by its decay the vegetable mould is con- 

 tinually augmented, and thereby the power of resisting washing is still 

 more ihcreased as the fertility of the soil is increased. This is but another 

 aspect and operation of the power of calcareous manure in soils to fix and 

 retain manures. 



The effect of marling will be much lessened by the soil being kept under 

 exhausting cultivation. Such were the circumstances under which we 

 may suppose that marl was tried and abandoned many years ago, in the 

 case referred to in page 70. Proceeding upon the false supposition that 

 marl was to enrich by direct action, like dung, it is most probable that it 

 was applied to some of the poorest and most exhausted land, for the pur- 

 pose of giving the manure a •' fair trial." The disappointment of such ill- 

 founded expectations was a sufficient reason for the experiment not being 

 repeated, or being scarcely ever referred to again, unless as evidence of 

 the worthlessness of marl. Yet with proper views of the action of this 

 manure, this experiment might at first have as well proved the early effica- 

 cy and value of marl, as it now does its durability. 



When acid soils are equally poor, the increase of the first crop from 

 marling will be greater on sandy, than on clay soils ; though the latter, by 

 heavier dressings and longer time, may ulfimately become the best land, 

 at least for wheat and for grass. The more acid the growth of any soil is, 

 or would be, if suffered to stand, the more increase of crop may be ex- 

 pected from marl ; which is directly the reverse of the effects of putrescent 

 manures. The increase of the first crop on worn acid soil, I have never 

 known imder fifty per cent., and more often it is as much as one hundred ; 

 and the improvement continues to increase, under mild tillage, to three or 

 four times the original product of the land. [See Exp. 11, page 86, and 

 Exp. 4 and 6.] In this, and other general statements of effects, I suppose 

 the land to bear not more than two grain crops in four years, and not to 



