1684 



IRRIGATION 



IRRIGATION 



or wooden pipes held together with substantial hoops. 

 If the depression is not too great the ditch may be built 

 up on an earth embankment. When the water has to 

 pass through a gravelly soil, or when for other reasons 

 the soil is very pervious, special precautions should be 

 taken to prevent seepage by using pipes, cementing the 

 sides of the open ditch, or puddling the ditch with clay 

 or similar material. 



Application of water. 



The water is usually applied to the ground by flooding 

 over the whole surface. For this purpose the surface 

 must be perfectly level and the ground carefully pre- 

 pared, so that the water will flow uniformly and quickly 

 over the entire area and be of uniform depth through- 

 out. When crops are cultivated in rows or on beds, 

 the water is allowed to flow down in the troughs between 

 the rows, and there must be a sufficient head of water 

 to reach the ends of the rows in a reasonably short time, 

 so that the whole width of the field will be properly 

 watered. 



Where the surface of the ground is so uneven that 

 surface flooding cannot be used, basins are formed by 

 throwing up slight ridges, with a plow or other imple- 

 ment, and the water turned into these basins in succes- 

 sion and allowed to accumulate to a sufficient extent. 

 This method is particularly applicable to fruit trees, 

 although it is occasionally used in other crops. In very 

 sandy soils the water is occasionally carried through 

 the field in wooden troughs, which admit of sufficient 

 seepage to water the land. This prevents the undue 

 seepage which might occur in such soils if the water was 

 flowed over the surface. Another method is to dis- 

 tribute the water through the field in iron pipes, with 

 openings at frequent intervals, in which nozzles can be 

 attached to deliver a fine spray over a small area. With 

 four or five such nozzles an attendant can water a con- 

 siderable area of ground in the course of a day. Such 

 an irrigating outfit in Florida was supplied with a 

 power equivalent to about one horse-power an acre. 

 The mains and laterals were of 1-inch or 1^-inch iron 

 pipes laid near the surface of the ground, the laterals 

 about 100 feet apart, with hydrants every 50 feet. Tanks 

 were originally used, but it was found desirable to 

 pump directly into the mains to insure a sufficient 

 pressure. 



Care should be exercised in applying water to the 

 land. Where water is plentiful there is a common prac- 



1979. Sutnirrigation with two runs of tile. 



tice of using such an excess as to injure the flavor of 

 fruit, increase the liability of disease, and eventually 

 injure the land by the accumulation of seepage waters 

 and of alkali. As a rule, there has been very much more 

 damage from over-irrigation than from the use of too 

 little water. The first two or three years a soil usually 

 requires a considerable amount of water, but after 

 becoming well moistened to a considerable depth it 



should require comparatively little water thereafter 

 to maintain its fertility. As it is not easy to apply just 

 the proper amount, the excess should be provided for. 

 If there is any reason to fear lack of drainage, the land 

 should be thoroughly underdrained before irrigation 

 is started, or at any subsequent time when the need 

 of it becomes apparent. 



Irrigation always should be supplemented by the 

 most thorough cultivation. After going to the expense 

 of watering the soil in this way, it is poor economy to 

 allow the water to escape by evaporation or otherwise; 

 therefore every precaution should be used in thorough, 

 subsequent cultivation and in the exclusion of weeds, 

 to conserve the moisture so applied. The intelligent 

 horticulturist will find that in the use of this expensive 

 method of maintaining a proper water-supply in the 

 soil, it is incumbent upon him, even more than if the 

 method were not used, to give careful attention to all 

 the ordinary methods of preparation and cultivation in 

 order to maintain the advantages he has established by 

 the irrigation plant. MILTON WHITNEY 



Sub-irrigation in the greenhouse. 



The term sub-irrigation is used to describe a method 

 of supplying water to the roots of plants by means of 

 some form of conduit placed below the surface of the 

 soil. In greenhouse operations, the essential features 

 of the plan are a level water-tight bench-bottom, and 

 tile, or pipes, to serve as conduits for the water. The 

 tile, or pipes, are laid directly on the bench-bottom, and 

 over these the soil is spread, usually to the depth of 

 about 6 inches. When water is introduced in sufficient 

 quantities through the tile or pipes, it passes out at the 

 joints, or perforations into the soil. 



When applied to greenhouse operations, the term 

 sub-watering has been proposed by E. S. Goff, for the 

 reason that irrigation is used to denote watering on a 

 large scale out-of-doors. It may be said, however, that 

 the words watering and irrigation do not indicate the 

 scale of operations with any degree of accuracy; there- 

 fore it seems as well to use an old word as to coin 

 one, especially when the familiar word expresses the 

 meaning intended. 



Experiments in watering plants by this method were 

 begun in the winter of 1890 and 1891, at the Ohio 

 Experiment Station. The suggestion came from the 

 result obtained in an effort to check the lettuce rot. 

 Water was introduced to the soil in boxes by means 

 of a pipe, in a manner similar to the method often 

 employed in watering hills of melons and cucumbers. 

 When the plants were watered in this manner, the let- 

 tuce showed so much more vigor than that watered in 

 the ordinary way, that operations were begun at once 

 on a larger scale; first in a bed on the ground having a 

 clay bottom, then on a water-tight bench, made of 

 lumber, and finally, on tile benches, covered with cement. 



In all of the earlier experiments the water was intro- 

 duced through pipes, or drain-tile, laid about 2 feet 

 apart on the bottom of the benches. Goff has used 

 brick instead of tile, placing them near enough together 

 to touch. They were set on edge in a galvanized iron 

 pan, made for the purpose. J. C. Arthur clipped off the 

 corners of the bricks, so as to facilitate the flow of 

 water. The Ohio Station has modified this plan by 

 using common drain-tile, laid so as to touch, thus cover- 

 ing the entire bench bottom, instead of lines of tile 

 every 2 feet, as at first. 



Benches made of lumber have proved unsatisfactory 

 because of the swelling and warping of the boards. 

 Solid beds on the ground have not been successful, 

 except where an impervious clay bottom existed. Gal- 

 vanized iron adds greatly to the cost of construction, 

 and lasts only a short time. The only suitable bench for 

 greenhouse sub-irrigation is one made of materials 

 which are not acted upon by water. 



