IRRIGATION

Press, Volume LXXVI, Issue 23086, 31 July 1940, Page 7

IRRIGATION

ITS SUCCESSFUL • OPERATION SOME OBJECTIONS DISCUSSED In the course of his address at the Jubilee function of Lincoln College Sir Francis Fraser (chairman of the School of Agriculture) dealt at some length with the question of irrigation. Sir Francis said that irrigation required a close study of conditions. One objection that was sometimes raised was that of cost. The Otago system cost the farmer from 7s 6d to 15s an acre foot: that is, 7s 6d to 15s for the equivalent of 12 inches of rainfall an acre. Australian systems cost from 8s to 12s an acre foot. Two American systems cost the farmer 7s B£d and 72s respectively an acre foot. The latter system, however, was in Southern California in a market gardening district, where returns were so high as to make it profitable to pay such a price for water. The Canterbury systems, on the other hand, were expected to cost only 2s 6d to 3s an acre foot, principally because the water supply came from constantly flowing rivers, requiring no expensive work on dam construction, and because the land sloped very gently and was almost flat, enabling races to be cheaply constructed. Another objection to irrigation had its origin in the conservatism of farmers who had for many years built up a system of dry farming, to which they had become accustomed, and with the returns from which—in a good season, at all events —they were fairly well satisfied. A third objection, which to some extent comes from a section of agricultural scientists, was based on the possibility of changed conditions of farming inducing stock diseases and disorders and creating other dangers and difficulties. He (Sir Francis) did not pose as the possessor of expert knowledge, but he proposed to discuss the two last objections from the point of view of a layman who had had an opportunity of hearing the opinions of experts. The first objection—that of cost—had klready been disposed of. The second objection—that the present system of dry farming was sufficiently good for the farmer —had nothing to support it, especially at a time when post-war problems had to be faced, and when the necessity of producing efficiently and economically was the dominant consideration. The plain underlying fact was that in a district with a low rainfall, of from 20 to 25 inches a year, the annual fall was generally insufficient to supply the moisture requirements of the plants throughout the year, and the land accordingly could not be worked to its full capacity. More particularly was this so in a district in which the rainfall varied from month to month and from year to year to such an extent as to cause periodic droughts, and in which drying winds caused abnormal loss of soil moisture through evaporation. It was obvious that the productive capacity of the land would be immensely increased if it could have a greater rainfall and a more regular distribution of that rainfall. This was exactly what irrigation provided, for the water could be turned on when it was required and turned off again when it was not required, thus giving a district such as Canterbury the benefit of the average North Island volume of rainfall without the disadvantage of the occasional destructive floods to which that Island was subject. Irrigation was to all intents and purposes a regulated artificial rainfall. Irrigation and an adaptation of farming methods to meet conditions similar to those of a high-rainfall district would enable the Canterbury farmer, once he had brought himself and his methods into, conformity with the new order, to show similar results to those achieved by his North Island confrere. The third objection to irrigation, to which he referred as coming from a section of agricultural scientists, related to the possibility of changed conditions inducing stock diseases and disorders, and envisaged' the whole subject of irrigation as being hedged round with potential problems and dangers. Other agricultural scientists held the view that all that was necessary was to transfer the knowledge available from a study of heavy rainfall conditions in the North Island, and apply that knowledge to Canterbury under irrigation conditions. They say in effect that, if soil conditions and other factors were similar, there was no difference between farming with an adequate, artificial rainfall and farming with an adequate natural rainfall. The two views appeared to be very far apart; but his own opinion, which was hazarded with all due diffidence, was that the difference between them was more apparent than real, and that, if the water was properly applied to the land, if the right type of pasture and the right methods of pasture management were adopted, and if the land was properly stocked with animals of the right types, the difficulties and dangers would soon be overcome. If a careful study of all relevant factors were undertaken before the . land was irrigated, the potential dangers and difficulties might never arise at all.