CENTRAL OTAGO: AFFORESTATION v. IRRIGATION.

Otago Daily Times, Issue 19205, 23 June 1924, Page 8

CENTRAL OTAGO: AFFORESTATION v. IRRIGATION.

TO THE EDITOR. Sir.—When we road (lint £3,0C0,0C0 could be successfully expended on irrigation iu Central Otago wti are confronted with tbe question: Do the results already achieved justify the expenditure of this money? It is now many'years since water was first used for irrigation purposes in Central Otugo. Iho gold miner hold the prior right to all water except what was known as the creek right —a portion which flowed down all creeks for domestic purposes, etc.; and which could be mined with, hut must he returned to the ercck. A nail from this there were small streams whin did not warrant any consideration from the miner, being too small to compensate him for the trouble and expense incurred in diverting the stream, the water from these two sources wan utilised by many farmers upwards of 50 years ego. In factj manv acres of land were irrigated in Central Otago Tong before some of the so-called originators of irrigation had ever left their native country. I remember when chaff from non-irrigated outs was preferable to irrigated, it. being perceivable at that time that tho irrigated oats contained less food value (gluten). This was considerably over 40 years ago. _ About this lime, also,* I saw a farmer irrigating a crop of potatoes, the means used being a self-improvised windmill pumping water to a height of about Oft and then running it in a V-shaped box to tho highest part of the field.

Practically all the land under irrigation for many years consisted of alluvial deposits —one of the best classes of land that can ho irrigated in Central Otago, being rich in humus and having a fair drainage. In addition, it contains rich deposits brought dpwn from time to time bv water from t.ne valleys and mountain sides, and it is chiefly tho results obtained from this class of land that have been the means of bringing 'these irrigation schemes before the public. There is no doubt that tho contrast is very great between tho green verdure of one of these deposits and the bare., barren hills.

But the land under the present irrigation schemes is not all alluvial deposits. A very large percentage could bo termed sedimentary soils, not to speak of the many other classes of alluvial deposits, etc., and it is the results obtained from some of these different soils and underlying strata that will determine whether irrigation in Central Otago is to be a success or not. Before proceeding further it may bo advisable for mo to confine my remarks to one particular scheme. Ida Valley. When we look at tabe 2, Government irrigation completed, in the March number of the New Zealand Journal of Agriculture, accompanying the articles by Messrs Torment and Marks, wo find that the area now being irrigated is 21,400 acres, of which 12. COO, _ or over half, are in Ida Valiev. One thing essential to the irrigator is that, he must have a thorough knowledge of the formation and character not only of the soil and subsoil but also of the underlying strata. For this he has to understand how the soil has come into being. With regard to Ida Valley, I favour the opinion that it was moraine dammed, as it gives a first-class example of being so. All moraine-dammed vnllevs drain out at their sides rather than at their ends through narrow gorge-like valleys. Ida Valley is confined by a solid bar , of rocks of high elevation on all sides but tho north-west, that position probably being filled with glacial deposit, thereby forming a lake, liven if it wgro not so the valley must cither have been filled with water , or ice to have cut its day down so as to form the Poolburn Gorge, and as it is a known fact that most lakes, as they become drained, leave behind them alkaline deposits brought about by chemical- and mechanical disintegration’ and the evaporation of filtered water, it would . not bo surprising to find that tho various' strata contain harmful salts.

The next matter of importance is the topography of the portion under the irrigation scheme and the classification of the soils which in the circumstances must bo mainly sedimentary end alluvial. Of the commonly called sedimentary soils, part should really he termed ‘'old alluvial deposits.” Although practically tne same on top, they are chemically different in the lower strata. Those old alluvial deposits apparently will not irrigate in conjunction wun the sedimentary soil. The same can bo said of the more recent alluvial deposits. Whether tne sedimentary soils can be successfully irrigated remains to ho seen, but the conditions prevailing in Ida Valley at the present time tend to show that drastic measures will have to be taken to avoid alkaline accumulations.

Messrs Tennent,; and Marks sfate that these dissolved,' salts are by capillarity brought to the, surface of the soil, where they arc deposited. That is quite so in most cases,- but it is generally applied to land that is devoid of fall or slope, but the portion of land in question in Ida valley has sufficient fall, and the trouble there is that these dissolved salts are probably brought on to the surface by gravitation. If that bo so, and I feel certain it is, it will prove one of the toughest problems to be faced in the matter of irrigation hi Central -Otago. This applies only to sedimentary soils. Drainage would be out of the question, and irrigation could only be carried on vorv sparingly, if at I heard of one farmer in Ida Valley who considers that the indiscriminate use of water which is practised on some of the farms was proving a success, as he had fattened more sheep per acre off that class of land than off land that was watered with more discretion. That may be quite true, and it probably goes to prove tne presence of a small percentage of salts held in solution, which at this stage only tends to make both the water and herbage pleasanter to the taste of most animals, ana also more nutritious. This small percentage has only got to accumulate fuither for a few years when the - hind will become useless, 'and it can be plainly seen that to try to avoid Una every farmer should be able to make a practical test as to the accumulation of these harmful salts. 1 this were done every year the farmer would soon ascertain whether his land was showing further deterioration or not. Ihis could be done quite simply. _ With regard to tho analysis of soil as shown in the March issue of the New Zealand Journal of Agriculture I doubt whether it is of much value to the farmer—that is. from an irrigation point of viewother than to indicate that tho land will respond to irrigation. Taking five chains ■m width and one mile in length from tho hill or mountain side direct to the lower part of the valley, it would he quite possible to find at least five different formations and characters of soil, each foimation requiring more Or less water, while on tho other hand some show more activity of growth than others. In the case of tile average fanner, practical cx|«?nonce gained bv careful study and observational regard to both agriculture and irrigation will do more to achieve a successful result than any table of chemical analysis usually shown. ’ ' , . _ Concerning tVie cinionnt* o* pt>vided by the Government and the water rentals a few words may not be out of place Tlien water allowed to the farmer* of Ida Valiev is one (ioveinniont head of water fer every 200 acres of land flowing continuously day and night for 150_ days. Previously, the farmers had tho equivalent of this in larger quantities taken in flushes at intervals The principal mode of using the water in Ida Valley is irrigation by gravitation. Tho land is ot a very uneven nature, and this, together with variation in the depth of soil, docs not afford an opportunity or the use or other mmheds that 1 are practised in irrigation projects throughout the world. Irigation by gravitation on land ot this description is pro' bahly one of tho worst, methods in vogi.ra at the present time, but this is inevitable. as lime wears on I think it will bo proved that tho changing from the larger quantities taken in flushes to a steady flow one head is a retrograde step, especially on land which is showing a slight deterioration. Further, it may probably be found that the Government’s method of distributing a slated quantity of water for a given area of land will not bo to the best advantage, as it is quite certain that the various constituents of the soil differ in their retention, percolation, and suitability to respond 1c- irrigation. Tin's diversity of soils will have a direct effect on whether the rents asked for can bo profitably paid, --ere for acre, there is no comparison be tween alluvial deposits and sedimentary soils either in the quantity of water required to be used or in tho amount of p-'-'dur-e that, can bo taken from the individual soils.

I not ice that comparisons of water rentals arc being made between the Central Otago irrigation schemes, averaging about 13s per acre, and those, of Ihe United States. The irrigation schemes cited in the United gtiitcs are Takiina. Valley, Washington, at about 15s 3d, and Southern California at 144 s per acre. We could also, have quoted Alodeslo and Thurlock irrigation schemes nt 2s 6d tier acre, or, going, further afield, have taken one cf' the Canadian schemes, such as Calgary, Alberta, where one canal 35 miles long is bringing water to 45,0f/0 acres, and the charge for irrigation is 4s per acre. The method of irrigating most of the land in tho Takima Valley is bv fm'row irrigation, tho object being to keep as much cf the surface dry as possible.

The soil, being of a fine clay loam, runs togcuicr, when wet, ami bakes and cracks wiic'n dry. These furrows are prepared belore seeuing us tne xarmer oojccrs to cutting up a held witn ditches. Bui, we have no need to compare tne lute of Ida Valley with Southern cunorma. tv e have a lair idea what Ida Valley can present in climate and produce, but a little intormalion concerning Balitornia may he ot benefit. JNo State in America has so great a variely ot sod and climate as California, and no State can yield such a variety 01 products. The temeperature of many ot its valleys is otten 110 to 120 degrees, which would he intolerable were it not regulated by ocean currents. Winter and summer are practically alike. Soma idea of the productiveness of the country can be garnered trorn too following .—Two crops ot potatoes can be grown in a year, three crops of figs or strawberries can be supplied any month in me year. Trees have been known to grow 2blt in a year. Beet has been grown weighing over lewe, cabbage over 8010, onions ift across, orange trees bearing each .4000 oranges, arid all with easy rail of cities up to one million population. One of these cities is at the present time reported to be increasing its population by 150,000 a year. Under these conditions hundreds of pounds can be taken oft an acre in a year. Jbouth California would have an advantage even at T2O an aero water rental over that of Ida Valiev at 10s per acre. Now let us have a look at the other side of the question—afforestation. The area estimated as probably irrigabic is quoted at 4C9,600 acres, but thousands of those acres will never be watered because the topography of the land is not suitable, "not to epeak of many pdrts of the slopes facing the south and south-west. But what of all the intervening land, amounting to, say, two million acres? What is going to be done with this ? It is a known fact that for the last 45 years this land ha s been slowly deteriorating. Irrigation cannot have anv direct effect in the prevention oi the denudation that is taking place. Allow me ro take exception to a statement by Messrs Tciment and Marks in the March number of the New Zealand Journal of Agriculture: “If no assistance were,given by co-operative endeavour t/entral Utago would be in 50 years’ time what it wa» 50 years ago.’" What a blessing it would be to Central Olago from an agricultural and pastoral point of view if all _ the natural grasses, scrub, and trees which adooned the mountain sides, valleys, and _ flats 50 year= ago were reinstated. 1 think that through the lapse of time we are apt to forget what Central Otago was like. Even 40 years ago crops could be grown, on an average, to greater advantage in Central utago tuan in ,-juutn Otago to-day, but as the hills, valleys, and fiats became devoid of vegetation the retention of water became less apparent, and irrigation, where water was procurable, was resorted to. When Central Otago was in it s natural -.tale and clothed witn vegetation it had an . insular climate, but denudation has taken., place to such an extent the last 40 years that to-day it has a strictly Continental climate. Those who have been engaged in agricultural and pastoral work for the last 60 years must have noticed the great less of Vegetation, and that the country has become drier, while those engaged in mining during the same period must have noticed the decrease in the amount of water flowing in the various creeks and small rivers. Irrigation may bo beneficial to only a portion, but afforestation would undoubtedly benefit the whole land. Even if it did not fulfil its specific purpose it would still be of monetary value as at the very door millions of feet of timber could bo used for fruit raises, do. Afforestation would not bo the drain upon the pockets of the settler that irrigation is. The initial outlay would be the only once for the trees would become more valuable as the years go by. There is no denying the fact that vegetation in the shape of trees and grass must bring about the retention and conservation of moisture. Forest, lands are always more or less damp tills being primarily due to the fact that trees chock the influence of the sun’s rays and of drying winds. Further, the extensive radiating surface of the leaves in comparison to their volume plays an important. piliT in the precipitation of moisture. Thus applies more to decidic.us trees than evoragreens owing to the more prolific leaf growth of the former. Daring the dryert part of last summer I paid a visit to Central Otago travelling via Roxburgh. 1 wits , considerably impressed bv the- green annearance of the hillsides adjacent to the fruit-growing area between Island Block and Coal Creek. In no other part did I notice such greenness, irrigated area-s excepted, for in no other part is there such an extensive i«d continuous area of richly foliagod deciduous trees. This appeal’s to mo to be a crowning testimony of the efficacy of deciduous trees in bringing about precipitation.

Central Otago is undoubtedly an almost rainless region, but it' is by no means moistureless. 'ITio normal summer climate of Central Otago does not present the conditions necessary to bring about the condensation of the aqueous vapour which is generally forced by the intensive heat to the higher strata of air. Extensive areas of trees would counteract this rising tendency of the aqueous vapour. It would do more. By the cooling of the lower strata of air the moisture-bearing currents would bo brought down and the moisture in them condensed by contact with the cooler air lower down. Sudden electrical disturbances and cloudbursts, which were practically unknown in Central Otago prior to 1882, would bo well nigh eliminated. These are of frequent occurrence and the damage they do in a decade must, be very great. The time is not far distant when the cry, “Irrigation is the salvation of the Central Otago,” will be, superseded by a. similar orv in favour of “afforestation.” Irrigation as an aid to the production of plant growth hag much to recommend it, but there is no gainsaying the fact that it is an unnatural way of supplying plants with the requisite moisture. To-day in the United States there are thousands of acres of land which have been rendered useless by irrigation. People the world over have only recently come to realise the great need for afforestation. It was not until 1919 that the first Afforestation Commission in Groat Britain was set up. Science mnv counteract the evil effects of irrigation, but at the best it can do little more than postpone the evil day. Wo should give a thought to the unborn millions who may yet require the use of the lands in Central Otago. In conclusion should there he the remotest possibility of reclaiming the depleted lands of Central Otago by afforestation, why, should the powers that be with their rather expensive public works burden the land with an everlasting debt, and thus for ever handicap the primary producers of the country in their endeavour to compete in the open markets of the world before trying a project that would compensate the country within 25 years whether it fulfils its specific purpose or not. —I am, etc.. j. C. Smith. Lovells Flat, June 17.