Page:Encyclopædia Britannica, first edition - Volume I, A-B.pdf/75

 A G R I C U L T U R E. 49 The operation of alhes upon the foil muft therefore be of the fame nature with that of lime, only it is more vioOf Shells. lent and fuddea, and confequently it is fooner over. This is confirmed by experience. After land has been Beds of IheJls are to he met with in many places, but manured with alhes, the firll crop is commonly very lux- particularly near the fea-lhore. uriant; but a fecond crop almoft entirely, exhaulis the Thefe Ihells ferment with acids, and, like other aniland. Hence alhes Ihould be laid on in fmall .quantities, mal-fubftances, contain oil, fait, and earth. Their opeand Ihould not be applied to land exhaulted by lime or ration is fuppofed to be of the fame kind with that of marie; neither Ihould they be repeated, or followed by Ihell-roarle : But, as they take a long time to dilfolve, their effefts muft be flower and weaker: They ought thefe manures. Burnt turf is generally recommended as a manure. therefore to be applied in large quantities, otherwife Turfs are chiefly compofed of vegetables ; their alhes, their operation will be hardly perceptible. therefore, mull; be of the fame nature with thofe of wood Shells exhauft the land, but not near fo much as lime or any other vegetable fubltance. It is found by experi- or afhes; it is therefore improper to ufe them immedience, that the burning of turfs turns out to advantage ately after thefe manures. in proportion to the number of roots they contain; and When Ihells are found below the furface of the ground, therefore land, with a tough fward of grals, is m ft as they generally are, they Ihould be expofed to the air for feme time before they are ploughed in: This not proper to be improved in this manner. In burning turf, the heaps mull be Covered in fuch a only aflifts their fermentation, but promotes their pumanner as to prevent the flame from breaking out; o- trefaction. therwife the moft ufeful part of the alhes will fly off. To prevent burnt land from being exhaufted, one or entire State, or fown for two crops only Ihould be. taken, and then the land Of Vegetables in anManure. ought to be laid out in grafs. Its fertility will be greatly increafed, if a little dung be added after the It is a practice in many places, particularly in Engfirft crop. land, to few turnip, peafe, buck-wheat, <&c. and to plough them down for manuring the land. This practice is thought by feme people to be attendOf Soot. ed with no advantage; becaufe the plants, when ploughSoo r contains oil, fait, and earth. It promotes ve- ed down, can convey no more food to the foil than they getation in the fame manner as dung or Ihell-marle. take from it. But it ought to be confidered, that feme Soot is generally applied in the Spring as a top-drefling of the plants employed in this manner pufti their roots to winter corn or grafs. The effects of foot ufed in this below the reach of the plough, and fuck up the food to way are fo fudden, that they evidently appear after the the furface; the feed that is fown likewife contains a firft rain. But its virtues are commonly exhaufted by a great-proportion of vegetable food; befides what the fingle crop. However, when the effefts of foot are owhen growing, may derive from the air, <fyc. Froot ver, the foil is not exhaufted, as by allies or lime;.it may plants, circumftances it may be inferred, that they actualtherefore be repeated as often as the farmer thinks pro- lythefereturn nourifliment to the foil than they extraCt per ; or it may be followed with advantage by alhes, from it. more The covering of the furface is alfo an advanlime, or marie. tage : Every farmer knows, that when the foil has been covered for a confiderable time by a ftrong crop of peafe, or any other corn laid down, the foil, though naturalOf Sea-weed. All plants that grow upon rocks, within reach of the ly hard and ftiff, becomes foft, mellow, and free. fea, are good manures. Thefe are frequently loofened Of Water. and driven a-lhore by the tide. They are of a foft pulpy nature, and foon putrefy. Rain-water contains a confiderable quantity of veSea-weeds promote vegetation in the fame manner as getable food. When it upon land that has a defeent, dung or foot; but their effects are not fo lafting as dung. by running off, it muft falls along with it feme of the However, they are preferable to dung in this refpeft, that fineft particles of the foilcarry and the vegetable food containthey do not produce fo many weeds. ed in them. If this water, then, is let in upon a field, and They may be applied to land in any fituation, and are allowed to fettle, the land will receive from it not only peculiarly proper for land that is exhaufted by lime or the vegetable food contained in the water itfelf, but alhes. When their effects ceafe, the land is not injured, likewife what is contained in the particles of earth carried and any kind of manure may bp ufed after them. from the higher grounds. The oftener fea-weeds are applied, the land becomes offThis method of manuring can only be in fields the richer. This is confirmed by experience. The which lie on the fides of rivers, or fuch as ufed eafily lands npar the Ihores, where the weeds have been long drained. In praCtifing it, the water muft notcanbebeallowed ufed as manures, are among the richeft in Scotland, and to run off violently, otherwife it does more hurt than have been kept almoft conftantly in tillage. good. Land in grafs is moft proper for this kind of Vol. I. No. 3. 3 N manuring.