It has become, in most of the cultivated parts of the globe, a serious and expensive matter to preserve the soils in lull bearing by regular and frequent manuring. The cost of lime, dung, and other fertilizing substances, is con siderable, and the cart iage and application add materially to it ; nor is it always in the farmer's power to apply his manures in the proper season, and to the requisite ex tent.
Irrigation supplies manure in favourable circumstances, at less expellee, and with more effect, than almost any other mode, on the soils to which it is applied ; and the produce of it on these furnishes increasing means for the manure of other sods. The limits of this beneficial opera tion appear us unfixed as its advantages arc liberal ; and as the population increases, these limits extend by the siniul tanenus enlargement of the means and the returns. It na turally connects itself with draining and embankment, and is therefore capable of great extension, as the radical im provements of a country advance. In short, whatever oc casional errors may be committed in irrigation, it is an art that will naturally and ought to advance, in any well go verned country, along with the population and general im provement.
The proper modes of conducting the operations of this art must he varied greatly in respect of particular circum stances. A flat soil requires to be floated in ridges by means of a full supply of water, the feeders on the crowns, and the drains in the furrows ; but this method is expen sive in the forming as well as in the supply of water ; it re quires land suitable for the plough, and therefore valuable otherwise; and it succeeds fully only when the waters arc and the climate good. All these circumstances, how
eve frequently concur in England to recommend it.
C itch-work is applied on dry barren slopes, where the operator sends the water in succession over different parts of the surface, accommodating his operations to the natu ral lorm of that surface. This method is attended with lit tle e:tnence, and may answer well in almost every case where water is not plentiful, and circumstances unfavour abl. to flat forming.
1. is an -rror to think that very long continued watering is )1uctiv• in proportion. On the contrary, irrigation not he coutir,ued for too long a time at once on any grounds, otherwise the fine: grasses and plants are there by destroyed, and a set of coarse aquatics brought up in tbeic place. Repeated waterings ItFe necessary indeed ; but the general practice does not seem to recommend above three weeks at one time in cold weather, half of that time ni moderate weather, and one week when the season is %.arm ; on the whole, about six weeks in the year.
In the pat tieular works and operations of irrigation—the precautions necessary when sheep arc to be fed on water ed lands,—the plants most suitable,—and the value and ap plication of the produce, we refer to those works already quoted, and others in which the peculiar practice of irri gating for grass in Britain is detailed ; including among these last the treatises written by Mr. Wright. Mr. Bos well, and Arthur Young, and the Highland Society Trans actions (K. h.)