IRRIGATION AND PASTURES

Press, Volume LXIX, Issue 20937, 18 August 1933, Page 7

IRRIGATION AND PASTURES

PROBLEMS FOR FARMERS ADDRESS AT GRASSLAND ASSOCIATION "There are large areas in New Zealand, particularly in Canterbury, where water would undoubtedly mean much in the successful establishment and maintenance of pastures, and one feels that at no distant date large tracts of poorly productive land will ultimately be converted into luxuriant pastures," said Mr R. B. Tennent, Fields Superintendent of the Department of Agriculture, in a paper entitled "Some Aspects of Irrigated Grassland," read to the conference of the New Zealand Grassland Association yesterday. "The question which immediately confronts the irrigation farmer who proposes to lay down a permanent pasture is the seed mixture which, should be used," said Mr Tennent. "So far as experience has shown there can be no question that the right type of perennial ryegrass and white clover stands out pre-eminently. On the Gal' loway Experimental Farm, in Central Otago, the most productive pasture was an old permanent ryegrass-white clover field, set down some 30 years ago with what obviously must have been a good type of southern ryegrass. The response of this pasture to irrigation has been astonishing, and despite the severe treatment which it has reI ceived, having been for a long time used as a ram paddock for Galloway Station, it to-day retains its pristine glory and is a striking testimony to the importnace of sowing the right strain of ryegrass. "Cocksfoot has failed entirely to prove its suitability as an irrigated grass, being low in productive ability, Ind having a much shorter period Of erowth than ryegrass. Poa pratensis, which is sometimes included in permanent pasture in the more humid areas is a pest with the irrgation farmer and should certainly not be included in any mixture. Clovers reonond to irrigation admirably, and the inclusion of white and alsike clover in a permanent pasture mixture is Pr fn^'the irrigation of grass either of two main systems, or their modificatiSS Sd be adopted, depending upon the grade%f the land. Where the pa?-j ture was on a fairly steep grade, contour irrigation should be adopted. This system was the only one whichcould be recommended for very steep land and was quite efficient for any slopes a a chain or steeper. It could be, SPiSS-SSf VS&M! ssL&sss TII sySTjrssrs of the land. Nt sys tem, considerbecarne a P_ amount of labour ably crops, and by its use in irngatmg! y what Bneth°nf8 ne th°nf water was being applied, a depth o first importance, particug?iy e wheJe the supply was restricted. Frequency of Watering. The frequency with which * "Irrigation was Of vital wo* be aimed Smts operated by m Government

the quantity allotted to farmers varied from 24in to 38in in depth for each acre of irrigable land, according to. the class of land upon which he was situated. Consequently he was wise who regulated his irrigations in such a manner as not to be left in the unhappy position of being short in the fall of the season. ThGre was no problem of such great importance as that dealing with the volume of water required to maintain growth successfully on pastures, and the utilisation of such water in the most advantageous and economical manner. In applying water to the pastures frequent light applications would give most profitable results. There were large ar6as of grass situated on sous with a water holding capacity of three inches, but the irrigators of these areas, Instead of dividing their yearly supply of 24 inches into eight irrigations of thr6e inches each, endeavoured to reduce the number of irrigations to four, applying approximately six inches at a time, only to find that the water supply was insufficient for maximum grass growth. The result of such practice in the past had led to the general belief among settlers that the Government allocation of water was too niggardly, and considerable pressure had been brought to bear With a view to having the suoply increased. Actually in such cases the trouble was that in each irrigation the soil had been over-saturated by at leasi three inches of water, which was lost by percolation. "A condition which faces the farmer of irrigate lands on such areas as Galloway, Soringvale. and Manuherikia, is the absence of humus or organic matter in the soil." said Mr Tennent. "To a considerable extent the very characteristics that make the arid land so desirable whm irrigated are necessarily inseoarable from their lack of humus at the start, and therefore the suDDjylng of humus should be treated as one of the steps in preparation of arid land —evactly like supplying an irrigation system. Autumn Ploothincr Necessary. "Where pastures are intended to be sown on tne heavier types of alluvial flats there is unfortunately a regrettable disregard of the importance of autumn ploughing. Too much stress cannot be laid on this procedure, particularly for the irrigation farmer. Deep tillage in the autumn enables the soil to absorb moisture from the winter snows and frosts in a quantity not possible in any other way, and it is an undeniable fact that such land will require one-third less water during the first season than land not so prepared. . "On certain limited areas in Central Otago farmers meet with difficulty in establishing pastures, and investigation shows that the cause of failure is sometimes due to the presence of either black or white alkali. These injurious salts are chiefly the chlorides, carbonates, and sulphates of sodium, or may occasionally prove to be the chlorides or sulphates of magnesium, potassium, or other salts. Their accumulation is slow and insidious, and one often witnesses pastures slowly deteriorating as the alkali gradually increases. When large quantities of water are applied to the ground a considerable proportion, of these salts are turned Into solution. Excessive evaporation follows excessive watering and the dissolved salts are by capillarity brought to the surface of the soil, where they remain. The use of fertiliser* for topdressing irrigated pastures was not as yet a common practice with irrigators, but the experiments conducted by the department at Galloway and elsewhere pointed conclusively to the fact that production could be very matenally increased by their use, and that the amount of water required for lmga. tion would be considerably lessened if this practice were adopted. The time was rapidly anwroacWns when topdressing aM limin* of irrigated pastures would have to be carried out as a routine practice, particularly with a view to encouraging early spring and late autumn growth of grass, and sufficient evidence had been secured to point conclusively to the fact that fhls result eould be attained.