CHAPTER XIII.
ON THE IRRIGATED MEADOW.
Irrigation, as a means of increasing the amount of pasturage, is so important a process that it may be well to describe it in this place.
For a perfect irrigated meadow, we should have full command of water whenever it may be required. This water should be capable of flowing through, not of pouring over, and standing on the land,—this latter being flooding. The drainage should be so perfect that the land will be sound enough for us to walk over in the dry in a few hours after the water has been turned off.
Where these conditions can be secured, irrigation will be found most useful, not only in augmenting the supply of grass, but in producing it so much earlier than in the higher meadows that the farmer hereby gets a fresh green pasture, of great utility, especially in fattening and bringing on early lambs. From these circumstances it follows, that although some land is occupied in the water-conduits, yet the value is so far increased that meadow at 30s. per acre before irrigation has, under one’s own eye, become worth £5 per acre in four years. There are, however, some necessary expenses in setting out the work, making floodgates, &c., the extent of which will of course depend upon the nature of the ground. In Gloucestershire, on the banks of the Churn, where irrigation has been successfully carried on for years, there is a permanent cost of about 6s. an acre for keeping the works in order, and charges of the “drowner,” the name given to the man who overlooks the works, in some instances of several proprietors or tenants.
A peculiarity in irrigated meadow of the best quality is, the general absence of coarse grasses on the one hand, and of any plants other than grasses on the other; hence, then, good succulent and nutritious herbage is the rule, and anything that can be otherwise described is the rare exception. Indeed, so much is this the case, that a bit of coarse grass—such, for instance, as Aira cæspitosa (Tussac Grass)—making successful growth in any part of the meadow, is at once an evidence of a stagnation of water at that spot—a condition that a clever drowner at once looks to when he has discovered it.
As an evidence of the changes which go on as the process succeeds, as well as of their nature, we give the following as the tabulated result of the irrigation of half of a meadow whose slope was too great to allow of the whole being operated upon. From these it will be seen that the proportionals of different pasture plants before and after irrigation offer a material change; and it may be added, that in some cases, what would otherwise be a bad and useless grass, may become succulent and useful from the beneficial action of water. One of this kind is the Agrostis stolonifera (Fiorin Grass), which is in arable couch-grass weed, but in the irrigated meadow it becomes of a fine green colour, is nutritive in quality, and will bear with any amount of clipping. It may here, too, be remarked that in cases where only a part of a meadow can be irrigated, good accrues to the whole, as in depasturing the whole is ranged over by our cattle and sheep.
We here give the following
TABLE OF CHANGES IN GRASSES AND OTHER PLANTS UNDER IRRIGATION.
| Trivial Names. | Botanical Names. | Before Irrigation. | After 2 Years’ Irrigation. | After 4 Years’ Irrigation. |
| Meadow Foxtail Grass | Alopecurus pratensis | 1 | 2 | 3 |
| Field Meadow Grass | Poa pratensis | 2 | 3 | 4 |
| Rough-stalked ditto | „trivialis | 1 | 2 | 1 |
| Quaking Grass | Briza media | 2 | 0 | 0 |
| Dogstail Grass | Cynosurus cristatus | 2 | 1 | 0 |
| Hassock, or Tussac Grass | Aira cæspitosa | 1 | 0 | 0 |
| Marsh Bent | Agrostis stolonifera | 1 | 2 | 3 |
| Cocksfoot Grass | Dactylis glomerata | 1 | 2 | 3 |
| Yellow Oat-grass | Avena flavescens | 2 | 3 | 3 |
| Soft ditto | „ pubescens | 1 | 1 | 1 |
| Meadow Barley | Hordeum pratense | 1 | 2 | 2 |
| Perennial Rye-grass | Lolium perenne | 2 | 4 | 6 |
| Meadow Crowfoot, or Buttercup | Ranunculus acris | 1 | 3 | 1 |
| Bulbous ditto | „bulbosus | 3 | 1 | 0 |
| Narrow-leaved Plantain | Plantago lanceolata | 3 | 1 | 1 |
| Broad-leaved ditto | „asiatica | 3 | 0 | 0 |
| Dutch Clover | Trifolium repens | 2 | 0 | 0 |
| Broad Clover | „ pratense | 1 | 2 | 2 |
| Common-beaked Parsley | Anthriscus vulgaris | 1 | 2 | 1 |
The general conclusions from this table are, that large and innutritious herbage is, for the most part, destroyed by irrigation, and its place is supplied by grasses; hence, then, the increased value conferred by the regulated action of water is due to an increase in quantity and quality of the grasses, added to a much more certain, as well as early, production of these. Of course the districts best adapted to irrigation will be valleys of denudation, the centres of which are occupied by more or less copious and rapid streamlets. Some of these valleys in the Cotteswolds having been scooped out of the oolitic freestones, have left the spoils of the rock as a gravelly deposit, sometimes on the lias, at others on the fuller’s earth, and then on the Oxford clays; so that, stiff as these soils would be by themselves, they now only tend to throw out the waters by natural drainage, which are again conducted over the porous gravels through which they flow with great regularity; thus fertilizing what would otherwise be but a scanty thin-soil herbage, and to such an extent that early depasturing, haymaking, and later pasturage (lattermath) are the rule year by year.
These circumstances make water-rights of great value, and which, if not in possession, are secured at a fixed charge per acre; this, however, is usually included in the expenses, which, as before stated, are covered by about 6s. per acre.
Before concluding this chapter, we must say a few words in reference to flooded meadows. These will be found on the banks of the larger rivers or on streams of sufficient importance to be called rivers, as distinguished from brooks or streamlets. Here the flooding is caused by the water overflowing the banks, as the result of sudden thaws or an unusual quantity of rain. Here then the flood is not under control, and as it may happen at any and all times of the year, the grass may be spoiled by being covered with silt and drifted materials, or even the hay may be carried away by the flood.
These river flats, then, have seldom the requisites for carrying on irrigation, although the waters are of course more abundant than those supplied by the smaller streams; for even if we could by embanking so far control the water as to get it over the field when we might wish, yet alluvial flats like those of much of the Thames and Severn would not readily drain.
From facts like these it will at once be seen that there is a wide difference between irrigation and flooding; and we have hence endeavoured to separate what is too often confounded.