Vízügyi Közlemények, 1956 (38. évfolyam)
2. füzet - VII. Kisebb közlemények
(23) supplied at one irrigation vary 011 the same soil according to the kind of crops. Accurate and uniform supply of water on a given soil is possible only by furrows or borders of adequate length. The required amount of irrigation water, or more particularly the length of furrow or borders depending on it, varies with the crop at hand, different each year. Accordingly the location of the temporary lateral supplying the furrow or strip with water cannot be stabilized. Irrigation of hay crops concerns Hungary very much ; irrigation by borders is of great importance. Accurate and uniform supply of water is assured by an adequate length of borders, but another requirement is the proper rate of supply. Depending on the condition of the soil in general a supply of 3 — G 1/sec of water is allowed for every meter length of the strip. If for facilitating machine work strips of 6 — 10 111 width are laid out, the temporary laterals are to have large capacities of supply in order to assure the necessary supply of water to the strip. Temporary laterals, nearly perpendicular to the furrow or border and therefore at a small angle to the contour line, will have large supply capacities only if their banks are compacted water-tight. Better compaction than hv rolling was attained by assigning the caterpillar tractor, which draws the ditching plough, to this work (Fig. Id — 18). The temporary lateral is therefore built in two operations, it is fit to keep a water level of 7 — 10 cm above the surface of the soil to attain the required supply rate of 30 — 50 1/sec. The gentle slope of the temporary laterals required by the suggested system imposes, of course, a limit on their length. In order to increase the width of the farm plots these temporary laterals are supplied with water from two sides. The minimum width may reach 260 111. This is more advantageous from the viewpoint of farm implements than the width of 100 111 previously applied. By this method plots of 20 hectares can be irrigated and even larger ones if the topography is favourable. Irrigation, uniform distribution of water over the plot, the application of temporary laterals is impeded by rolling topography obstructing the passage of water. Such ground lias to be graded. Counter-slopes are least probable to occur along the line of the natural slope of terrain. Least earth-moving is to be expected if furrows and borders conform with the general slope of the terrain. Earth-moving will also be reduced if the location of temporary laterals is fixed and the ground is graded crosswise only at their places. Of course, thereby the possibility of uniform supply of varying rates of irrigation water will be limited. Varying rainfall conditions of Hungary call for drainage along with irrigation. Therefore on the deepest side of the plot a drainage canal has to be established into which excess water occurring on the plot are to be discharged. For drainage of harmful waters available furrows, strips, temporary laterals, or emergency ditches drawn along the deepest line of the plot may be used. The plot is approached most practically by a road, along the drainage canal. In this case a culvert has to be placed in the drainage canal only at the crossing of the approach. The farm lateral 011 the top side of the plot could be crossed only by a more expensive inverted syphon which would also involve a loss of head for irrigation, not permissible on very gently sloping land in Hungary. It is pointed out that the suggested scheme cannot be applied mechanically. The implementation of schemes must be decided in the light of local conditions. In general, however, the scheme suggested has proved successful in this country and is commendable for wide application. In Chapter I. some novel concepts are defined, in Chapter II. factors decisively affecting the development of large-scale irrigation farming is analyzed. Chapter Iii. reviews the pertinent literature, Chapter IV. accounts for experiments made in Hungary. Finally Chapter V. describes in detail and presents motives for the aforeoutlined suggestion tailored to conditions of the Great Hungarian Plain.
