396 LENGTH OF TIME DURING WHICH LI3IE ACTS. 



very much like the lime-sand of Ireland or the shell-sand of the West- 

 ern Islands already described (p. 371). A layer of this marl one-third 

 of an inch thick, applied at intervals to a soil producing in its natural 

 state only a threefold return of rye every other year, causes it to yield 

 for the first 10 or 12 years an eight-fold return of wheat. But after 40 

 years' marling, the farmers now complain that the land will give only a 

 four-fold return of wheat. But the cause of this reduction is to be 

 found in the constant cropping with corn, in the growing of no green 

 crops, and in the addition of no manure. Yet even with this treat- 

 ment the land is still more productive than before the marling was com- 

 menced. It produces four returns instead of three, and it grows wheat 

 where before only rye would thrive and ripen. 



From the possession of this exhausting property has arisen the al- 

 most universally diffused proverb, that lime enriches the fathers hut 

 impoverishes the sotis. The fault, however, is not in the lime, but in 

 the improvident fathers, who in this case, as in so many others, exhaust 

 and inconsiderately squander the inheritance of their sons. If care 

 be taken to keep up the supply of organic matter in the soil — by copi- 

 ous additions of manure or otherwise (p. 380) — lime may be added 

 freely and a system of high farming kept up, by which both the pres- 

 ent holder of the land and his successors will be equally benefitted. 



The opinion expressed by some of the highest authorities among 

 practical men, that too much lime cannot be added, provided the soil 

 abound sufficiently in vegetable matter, may perhaps be rather over- 

 stated ; but it undoubtedly embodies the result of long-continued gen- 

 eral observation — that the exhausting effect of lime may be postponed 

 indefinitely by a liberal management of the land.* 



§ 18. Length of time during which lime acts. 



It is the fate of nearly all the superficial improvements of the soil, 

 that they are only temporary in their duration. The action of lime 

 ceases after a time, and the land returns to its original condition. The 

 length of time which must elapse before this takes place will depend, 

 among other circumstances, upon the quantity of lime added to, or ori- 

 ginally contained in, the soil — upon the kind of cropping to which it is 

 subjected — on the nature of the soil itself— on the slope and exposure 

 and natural moisture of the land, and on the climate in which it is 

 situated. 



We have seen that on the arable lands of the south of Scotland 20 

 years is the longest period during which the doses there applied act 

 beneficially upon the crops — while in other parts of the country re- 

 newed applications are considered necessary at much shorter intervals. 

 Mr. Dawson, of Frogden, who introduced the practice of liming into the 

 Border counties of Scotland, observed that, when harrowed in with the 

 grass seeds, its effect in improving the subsequent pasture was sensible 

 for 30 years after. A heavy marling or chalking* in the southern and 



' In Germany the necessary union of manure and marl is in (he mouth of every peasant— 



— Ohne mist 



1st das Geld fur mergeln verquist. 



T Applied at a cost of 30s. lo 50s. per acre, accc fing to the localit; —Mr. Pusey, 

 Agricultural Journal, iii., p. 186. 



