Art. XXV.—On Irrigation as applied to the growth of New Zealand Flax.
[Read before the Wellington Philosophical Society, August 14, 1869.]
There is no country in the world which rejoices in more numerous sparkling streams than New Zealand, and in this respect it contrasts remarkably with the neighbouring territory of Australia; but the rivers are seldom navigable to any distance from the coast, and their waters generally reach the sea without proving of more utility to mankind, than for the common supply of liquid for daily consumption.
There are two modes by which the streams may be made useful to mankind.
By forming reservoirs of power.
By fertilizing the soil by irrigation.
It is my intention at present to consider the latter point only.
In Europe two systems of irrigation are adopted. In the warm climates of the Mediterranean basin, water is conveyed to the fields under crop, for the simple purpose of providing the necessary moisture.
In the colder latitudes of England, France, and Germany, water-meadows are put under irrigation during the winter season, at a time when, primâ facie, one might suppose that the soil was sufficiently moist. These meadows are laid out on two plans: on level ground they are formed into ridges and furrows— the water running on to the ground along conduits on the top of the ridges; then flowing gently over both sides, is carried away by the drain in the furrow. To lay off land carefully in this manner is expensive, but the returns are very great. On uneven ground the catch meadow system is adopted. Advantage is taken of the inequalities of the ground to run the water as evenly as possible over the surface, and with proper skill and judgment this object is often attained at slight outlay.
It is a remarkable fact, that although the fertility of water meadows is vastly increased by an admixture of manure with the water, yet that water, containing apparently no foreign element of fertility, is capable, when applied to the soil, of enabling it to return, year after year, heavy crops of hay and grass. This is a point which science has not, as yet, thoroughly explained.
As examples of irrigation I will mention the water meadows near Edinburgh, which are irrigated by strong town sewage. These meadows produce frequent heavy crops of grass, and are said to make a return of from £20 to £60 per annum, according to distance from the fertilizing sources, and the nature of the soil. In Wiltshire, Berkshire, and many other counties in the south of England, the return from water meadows, irrigated without sewage, is very large, and I think that, at a moderate estimate, a return of from £5 to £7 per acre may be considered the average.
The meadows provide early grass for the ewes and lambs in spring, a heavy cut of hay in summer, and an aftermath in autumn.
From my own experience, in a cold district in Scotland, I may state, that after throwing the drainage water from the upper part of my property, so as to irrigate some fields on the lower part, I have obtained, ever since, an increased return, of some 75 per cent. from the irrigated portion, over the previous rental.
In New Zealand, and in no part of the country more than in the Province of Wellington, there are facilities for irrigation possessed by few other countries. It would be absurd to advise expensive modes of laying off land for irrigation, in the present sparse state of the population of the colony; but if it should appear that large tracts of country may be irrigated at moderate expense, for the purpose of developing a staple export, the subject is at least worth enquiry. The export of the fibre of the Phormium tenax has
almost now become a settled industry, and although we may expect this year to hear of many samples being sold below cost price, on account of bad preparation, yet there is reason to suppose that all well-got-up samples will fetch remunerative prices.
Should this industry prove successful, it will clearly be necessary that the cultivation of the plant shall be proceeded with on a large scale, and no one who has observed the growth of the plant, but will have perceived the enormous advantage which irrigation may produce in the returns to be derived from it. If a drain be cut through a flax swamp, and the stagnant water thereby set in motion, the stunted flax, of 18 inches or 2 feet high, immediately springs up to a height of 8 to 10 feet. It is said that in the old days of Maori flax cultivation, the plants were irrigated, although always planted on a hill side.
There is, I should think, no disputing the point that irrigation would add immensely to the returns to be derived from flax cultivation.
It remains, therefore, to be considered what districts in this province are most favourable for irrigation.
Excluding, at present, any small valleys in this immediate vicinity, and proceeding to more extensive districts, we find a low-lying country of sand-hills, swamps, and alluvial flats, extending from the coast at Paikakariki to the Rangitikei river. This country is intersected by streams and rivers, and a great quantity of, at present, comparatively valueless land, might, by irrigation, be made to yield a large annual return. Among the rivers on this coast, the Manawatu might be used for what is called warping—that is, it might be made to deposit its sediment over unfertile tracts of sand.
On the Wairarapa side, extensive stony plains, which, without irrigation, can never produce much beyond a scanty herbage, might, by the fertilizing power of water, be made some of the most valuable lands of the colony.
To produce the results proposed will require both capital and skill; but, if the fibre of the Phormium tenax is to become a great staple export of this country, both of these must be found. If they are not procurable in the colony they must be imported. At the same time, laying off the land for flax irrigation would, probably, not be expensive.
Irrigation, once introduced, would be found to assist materially in the growth of numerous productions, and would, by no means, be confined to the growth of flax alone. Probably few persons in this province are aware that irrigation is at present carried on with marked success in the interior of the Province of Otago. Water-races, which have been brought into auriferous localities for the extraction of gold, are partially used for the promotion of the production of herbs and corn, and the enormous turnips, and other vegetables, which I have seen produced by this means, are enough to astonish a beholder.
I have pointed out the districts in this part of the island to which I consider irrigation might be most advantageously applied. They are low-lying compared with the levels of the streams. In other parts of the country, with the exception of the immediate banks of the rivers, the land rises too rapidly towards the interior to admit of the requisite facilities for the watering of its surface, unless at an expense which is not, in this generation, likely to be incurred.
Let us, however, remember the Spanish proverb:
“En Andalusia la carne es yerba,
La yerba es agua,
Los hombres son mujeres,
Y las mujeres nada.”
In Andalusia flesh is herb,
Herb is water,
Men are women,
And women are nothing.
Andalusia is a province in which irrigation is largely carried on.
Lest this proverb should produce any damaging effect upon our proposed scheme of irrigation, I may mention that I breakfasted one morning in Cadiz, and, that, so far as I could judge from such a cursory glance, the men were sturdy, and the women beautiful; besides which, I have had opportunities at Gibraltar, of observing the race with a satisfactory result.