122 CALCAREOUS MANURES— PRACTICE. 



Thus, in the three experiments 4, 9, and 1 1, the putrescent manure applied 

 was in quantity much too great for the calcareous earth to combine with at 

 once, even if the recent and irregular scattering of both kinds of manure 

 had not prevented their meeting in proper proportions. For like reasons, of 

 all the putrescent manures applied on the farm, and since larger quantities 

 have been used, there is much more of early than continued effect. Still, so 

 far as known and believed, there is always more or less of abiding effect, 

 and which I infer will be permanent. 



But wider scope for observation has been afforded in the increasing pro- 

 ductiveness of all the marled lands, kept under what was deemed not too 

 frequent tillage. Neither has the tillage been always mild, nor the rotation 

 uniform, and latterly the grain crops have been made more frequent 

 than before, and much more grazing permitted. Still, even where no 

 prepared putrescent manures have ever been applied, and putrescent mat- 

 ters have been furnished only from the growth of the land itself during its 

 share of rest in each course of crops, there has been a regular increase of 

 productiveness of the grain crops, in every successive rotation. In one 

 connected clearing, of what I found as poor forest land, now making 85 

 acres, the marling was commenced in 1818, and has been continued, as the 

 successive clearings extended, to 1841. The earliest effects of the applica- 

 tions were always satisfactory, but they have regularly and largely increased 

 with time. Thus, when under the last crop of corn, (in 1839,) the crop on 

 the last finished marling, though perhaps thereby nearly doubled in product, 

 was obviously and considerably less than that of four to six years earlier — 

 that again as inferior to that of the marling of ten to fifteen years — and the 

 crop on the marling of 1821 and earlier, decidedly the best of all, under 

 circumstances otherwise equal. For the limited time of 23 years, and 

 without any careful and accurate experiment or observation having been 

 made for this special object, there could not well be stronger practical 

 proof of the permanency of the vegetable manures stored up by the marl. 



If we keep in mind the mode by which calcareous manure acts, its 

 effects may be anticipated for a much longer time than my experience ex- 

 tends. Let us trace the supposed effects, from the causes, on an acid soil 

 kept under meliorating culture. As soon as applied, the calcareous earth 

 combines with all the acid then present, and to that extent is changed to 

 the vegetable salt of lime. The remaining calcareous earth continues to 

 take up the after formations of acid, and (together with the salt so pro- 

 duced) to fix putrescent manures, as fast as these substances are present- 

 ed, until all the lime has been combined with acid, and all their product 

 is combined with putrescent matter. Both those actions then cease. Diir- 

 ing all the time necessary for those changes, the soil has been regularly 

 increasing in productiveness ; and it may be supposed that before their 

 completion, the product had risen from ten to thirty bushels of corn to the 

 acre. The soil has then become neutral. It can never lose its ability 

 (under the mild rotation supposed) of producing thirty bushels— but it has 

 no power to rise above that product. Vegetable food continues to form, 

 but is mostly wasted, because the salt of lime is already combined with as 

 much as it can act on ; and whatever excess of vegetable matter remains 

 in the soil, is kept useless by acid also newly formed, and left free and 

 noxious as before the application of calcareous earth. But though this 

 excess of acid may balance and keep useless the excess of vegetable mat- 

 ter, it cannot affect the previously fixed fertility, nor lessen the power of 

 the soil to yield its then maximum product of thirty bushels. In this state 

 of things, sorrel may again begin to grow, and its return may be taken as 

 notice that a new marling is needed, and will afford additional profit, in the 



