The liquid portions of excrementitious manure likewise recptire either to be diluted with water or to receive an admixture of soil before they are brought in contact with the roots of plants. In the case of trees with roots lying deep in the ground, such dilution is not always necessary; but, generally speaking, adherence to the rule is advisable.
Flesh, or the caresses of dead :animals, should be chopped up and covered and mixed, with many tunes their bulk of soil and witl. some lime. This, when turned over, will still form a very strong manure, and for seine plants much too strong; but for such as the vine it will form a valuable compost, particularly if broken bones are added to it.
Manures derived from the vegetable kingdom require little prepara tion if they consist of succulent plants ; their substance is easily soluble, and they may therefore be turned fresh into the soil. The period of their growth when this is most beneficially performed is before they run to seed. Weeds may oven be used with great advantage, if properly prepared; but bad consequences may result from their seeds rendering the ground foul, and thus occasioning much expenditure of labour to extirpate them again Seeds, it is well known, will not germinate without air ; but with this, And sufficient heat and moisture, nothing can prevent them from germinating. Therefore if weeds be thrown into a heap and turned, whilst at the same time fermentation is encouraged till the heat is fully equal to that which would naturally cause the germination of the seeds, faking care that the outside be turned into the centre, no danger will arise from losing such manure after the process has been continued sufficiently long for the germina tion of the slowest vegetating seeds which the heap may contain, because under these circumstances the young plants will be continually perishing as the heap is turned over from week to week. There are many aquatic plants that will not grow on dry ground, and a prepara tion similar to the above is not essential for the purpose of killing their seeds before their application to dry ground, which is not, ao to speak, their proper element.
Woody fibre unfermented is useless as a manure ; and tanner's spent bark, a substauce very absorbent and retentive of moisture, is not capable of affording nourishment, until the tannin is got rid of by fermentation, when plants. as may be observed in bark-beds, root very
readily in tan. Inert peaty matter is a substance of the same kind, and will remain for years exposed to air and water without under going change. When peat becomes inert, it is in vain to attempt to grow any sort of plant in it ; but nothing is more certain than that if drained of stagnant moisture and mixed with lime and dung, it will become very fertile for most crops. It often happens that peat or frequently procured at a great expense for American plants, becomes inert ; in such cases, a good result would be obtained by turning out the peat and mixing it up in a heap with a quantity of leaves or fresh litter sufficient to promote a moderate degree of fermentation ; then, as in the case of tan, it will afford nourishment, and will, from a state-of uselessness, become valuable.
Of mineral manures lime is the most useful. It is not recommended for soils that contain a large proportion of soluble vegetable matter ; but it produces excellent effects in such as abound in inert vegetable fibre. Gypsum, which is found in the ashes of grasses, proves a manure for lawns.
Common salt is sometimes employed in minute portions ; especially in combination with vegetable matter, in the instance of sea-weeds, in which case it is found of good quality for fruit-trees and kitchen garden crops ; but vegetable life is certainly destroyed by it, if applied in any considerable quantity. Exceptions may be noticed in the case of marine plants; the samphire for example, requires it when cultivated in inland districts ; and this is also true of the vegetable inhabitants of the great salt plains of Asia. Wood-ashes, which consist principally of vegetable alkali united to carbonic acid, are a good manure, but of short duration, and they leave peaty soil in a worse state than before their application. The application of dung and lime, of composts of clay, marl, scourings of ditches, &c., wonld render peat permanently fertile, more especially when draining is judiciously attendixl. to.