8 Feb., 1908.] Preparing Land for Irrigation. 115 



the bottom of the checks than the contour method. This is expensive and 

 involves too much disturbance of the surface soil. Furthermore in rectan- 

 gular checks the levees have to be of varying heights and this makes it 

 more difficult to pass machinery over them. 



Rectangular checking is chiefly used in the irrigation of orchards and 

 gardens, in this, making a furrow alongside the levee is not as objection- 

 able as it is in lucerne growing, and the usual practice is to throw two 

 furrows together with an ordinary walking plough. An implement known 

 as a ridger can be used in light sandy soils. (Fig. 7.) 



4. Flooding by means of Borders. — Land is prepared for irrigation 

 by the border method by building low flat parallel ridges or levees from 

 I to 3 chains apart across the field and in the direction of the steepest 

 slope. (See Fig. 8.) The ridges are made in the same way as the checks 

 in the contour check method, the aim being to make the space between 

 the borders as nearly level as possible. 



A head br supply channel runs across the field at the upper end of the 

 strips and a large enough volume is turned out to cover the whole surface 

 between the borders. This is kept running until the water has gone from 

 two-thirds to three-fourths of the way down the slope when it is turned 

 off. With a skilful irrigator but little water will waste at the lower side 

 of the field. This method of irrigation requires a large flow of water, 

 600 c.f.m. is the quantity usually handled by one irrigator in California. 

 Half that amount would answer in the clay soils of Victoria. 



5. Percolation from small Furrows. — Flooding by contour checks 

 and borders is cheap and rapid and for land which will not run together 

 and bake is the best method to follow, but for stiff clay soil it is an 

 advantage to avoid wetting the surface, and where the surface is uniform 

 ■enough to permit water to run down furrows without breaking oxex the 

 sides and flooding the surface this plan has manv advantages. 



Fig. 9. Lath Tube for Ditch Bank. 



To irrigate lucerne bv small furrows the head ditch should run along 

 the side of the field from which the most uniform slope can be obtained. 

 This head ditch must be divided into level sections by means of drop boxes 

 if the surface has much slope. The lower bank of each section of the 

 head ditch must be graded off to an exact plane, which would" be about 

 6 inches below the surface level of the w^ater when the ditch is filled j on 

 this are placed small tubes long enough to pass through the ditch bank and 

 spaced the same distance apart as the furrows. This will vary from i to 

 4 feet, depending on the character of the soil. The tubes are commonly 

 made by nailing four laths together. This gwea a tube 3 feet long with 

 an opening i inch square. (Fig. 9.) Tin tubes are sometimes used and 

 in Ardmona a cheap tube is made from w^orn out gas pipes bought in 

 Melbourne. For most Victorian soils the tubes should be placed about 

 2 feet apart. A man can set from 40 to 50 of the tubes in a day ; an 

 expert setter will place 80. Placed 2 feet apart there will be 660 in a 

 ditch 80 rods long. If the furrows running from the opening are 80 rods 



