But apart from the general influence of lime on the soil, there is to be considered the relation in which it stands to the several the farmer cultivates.
Immense differences exist among our agricultural mops as regards the quantity of lime which they contain. Thus the ash of wheat-straw contains 6 per cent of lime, of barley-straw 8 per cent., of ryastraw per rent., and these crops accordingly do not take more than 10 to 15 lbs. of lime out of an acre by the growth of an ordinary bulk. Bean-straw on the other hand, or rather the ash of bean-straw, contains 21 per cent of lime, the ash of the pea 55 per cent., of the vetch 38 per cent—much Inrger quantities', and so an ordinary crop of beans and peon rtespectivtly will take by means of the one 33 Ilse, and by the mean,' of the other 190 lbs. of lime from the acre. Both of these crops therefore, on the ground of direct use of the lime for food, require II larger quantity of calcareous matter in the soil.
Take now the case of some of the root crops: we have in turnips, bulb and top respectively, hone to the extent of 11 and 23 per cent of their ash respectively ; in the case of mongol() a mailer quantity, namely, 3 and 8 respectively; in the case of the potato, 2 and 17 per cent. rcopectively ; in the case of the carrot, 8 and 32 per cent. respectively; in the case of Ineern again, which especially prospers on calcareous Ran, one-half of its ash in lime. Au examination of the ash analyses of plants shows the composition of the crops which they indicate to tally with agricultural experience as to the character of the soil they prefer. Thus the ash of the hicern contains 50 per cont. of lime, and that of sainfoin 29 per cent. These figures accord ingly prove that the influence of limo as a manure, does to some exscrit depend upon its power to supply plants' with direct food.
We turn now to the more direct manures—these which really con tribute the bulk of those materials towards the growth of plants in which the natural soil and air, the only other amines of nourishment open to them, are deficient.
The first and most important class of manures aro the excrements of animals. The peculiar property of earth in absorbing putrid effluvia and removing disagreeable smells, appears an indication of nature to lead us to bury putrid animal subotaneee, of which the excrements and dead carcasses of animals aro the most numerous and obvious. It would require no length of experience to show that wherever this is done vegetation is more vigorous. There is therefore another motive for burying dung than merely to get rid of n disagreeable aubetance. From the most ancient times of which there are any records, the (lunging of n field has been an important part of cultivation. The pre paring of the dung of animals, so as to render it more efficacious, is a later improvement, and has not yet attained the perfection of which it is capable, unless it be so in China, of which wo read wonderful accounts. The fresh dung dropped on the ground, far from improving
the herbage where it has fallen, appears to injure it, and render it unfit for cattle to eat ; when it gradually disappears, and not till then, the spot in restored to its former verdure. But if the dung be dug into the ground and covered with earth, the fertilising effect will be imme diately perceived. This is a sufficient lesson to the husbandman to mako him bury the dung as soon as possible. But this not being always practicable, it is collected in heaps until it can be carried to the Land prepared for its reception by ploughing or digging. By mixing the straw, which has served as litter to cattle, with their dung, the quantity is increased, and by allowing this mixture to heat and putrefy, a greater quantity of manure is produced This is probably the history of the dunghill. In the making of a dunghill, experience has taught methods which accord well with what science might have taught. The manure must be soluble before it can be effective ; this solubility can only be produced in the more solid portions, such as the straw, by putrefaction, which the dung promotes when duly moistened. The exact moment when it is most edvantag,eous to bury it in the ground, in order to its greatest immediate effect, seems not yet fully decided. Some let the decomposition go on until a great portion of the heap is converted into a black, tough, greasy substance, which, from early associ ation, gives the idea of richness. It is no doubt a powerful manure which acts speedily, but is it the most economical f This may be disputed. A great portion of the substance must have been resolved into gases, which fly off' and arc lost. The remainder, evidently car bonaceous from its colour, has acquired too much of the appearance of charcoal to be very efficient; and it is only the exuding juice which is immediately fertilising. The most experienced farmers agree, that whenever the brown colour of a dungheap verges towards a black, the dung has lost something of its value, besides the diminution in its bulk by dissipation. The best state in which dung can be carried to the land, for an immediate as well as permanent effect, is when the straw is so rotten that it readily breaks into short pieces, without having entirely lost its form : it should than be of a brown or maho gany colour, uniform throughout the man, Whenever dung is mentioned by foreign agricultural writers, it is generally understood to be in this state, which in English is called short dung. It must how ever be admitted that farm practice is more and more sanctioning the doctrine of the chemist, that it is true economy to bury manure as soon as we have it.