SPRINKLER SYSTEMS - 9
Burying the pipe
All of the soil that was removed from the trench should go back into it without difficulty. It should be returned to the trench in moderately thin layers, and each layer should be tamped somewhat before the next layer is placed upon it. If it appears, when the trench is about half filled, that all of the soil is not going to go back into it, wet thew soil in the trench thoroughly. Water helps materially to settle the soil and to carry it into pockets that may be left vacant even after vigorous tamping. When the trenches are filled and covered again with turf, they should be even with the adjacent soil. If there is any variation in the level of a newly filled trench, it should be a slight mound rather than a depression. A depression will grow worse as time passes, whereas a slight mound may eventually settle to the level of the lawn. Sometimes it happens that the soil of the lawn contains loose stones, and it seems to be a quirk of human nature that these stones will be sorted out and carried off. Carrying them off is justifiable if it is done in anticipation of the necessity of digging up the pipe lines at some future date. However, it is well to bear in mind that the stones do occupy space which, if the lawn is to be level after the installation of the irrigation system, should be filled in with an equivalent amount of soil. This means bringing soil to the trenches from some other place. 350. Re- laying the turf. Before the cut turfs are replaced, it is good practice to moisten the soil on which they are to be placed. In fact, if you are nervous about the re-rooting of the turfs, it is not a bad idea to make up what the gardeners call a starter solution. This can be done conveniently by dissolving a handful of fertilizer in a large sprinkling-can of water. If this solution is sprinkled over the soil, it will speed up somewhat the process of re-establishment. However, do not use too much fertilizer or there will be dark green streaks in your lawn for some time. The turfs tend to increase their bulk somewhat during the short period when they were detached from mother earth; and consequently when they are replaced, they may stand slightly above the surrounding turf. A good way to correct this is to soak the lawn thoroughly, using the newly installed system, and then to roll the strips with a light lawn roller. If the soaking has been thorough, relatively light pressure will restore the original level.
OTHER TYPES OF SPRINKLING SYSTEMS
All of you who play golf, and some of you who don't, are familiar with the fact that many golf fairways are watered with large rotating sprinklers. This type of sprinkler is used on large areas, not because it does any better job of wetting the turf than the type which has been described, but because it is cheaper to install. Note that only a single underground line of supply pipe is required to cover a large breadth of grass. This relatively broad coverage is possible because one of the large sprinklers has a "throw" that is several times greater than the "throw" of a regulation lawn sprinkling head. A variation of this system which requires even less pipe for an equal area of grass. Here, instead of attaching the rotating arm directly to the riser, a length of hose is attached to the riser and the sprinkler is attached to a fixture at the opposite end of the hose. By moving the sprinkler fixture from time to time, a much larger area can be covered from one riser.
Using large rotating sprinklers
ystems of this type are as adaptable to the needs of large estates with expansive lawns as they are to golf courses. However, they are neither so adaptable nor so convenient as the kind of system in which stationary heads are used. The borders of the area watered are somewhat uneven because it is not possible to do as precise a job of sprinkling the borders of areas as can be done with stationary heads. Another bad feature from the homeowner's point of view is that the attaching of the sprinkling head is a manual operation. The sprinkler must be attached and allowed to operate for one or more hours; then, in order to cover another area of grass, it must be moved. Such tasks are all in the day's work for professional gar- deners, but they don't fit well into the routine of the average homeowner. Still another variation of this idea does away entirely with underground piping. Instead of the buried supply pipe, a portable supply line is used. Portable lines are made of lightweight tubing and are equipped at the ends with special fittings which permit the length of tubing to be virtually snapped together without special tools. Short risers are attached to some sections of tubing, and the sprinkling heads are attached to the risers. Both the sprinkling head and the tubing must be moved about in order to operate the system.
Irrigation with overhead lines of pipe
Irrigation from overhead pipe lines is an old technique in vegetable gardens, especially in areas where such gardening is carried on intensively. We shall make no attempt here to discuss large systems of this type, but small systems consisting of one or two lines of pipe are of interest to some homeowners because of their potential use in the home garden. In irrigating large truck gardens, the pipe lines are usually installed permanently and are placed high enough so that horses and tractors can be driven under them without interference. In the home garden it is often more convenient to use two pipe lines, one on each side of the garden, than it is to have an elevated line of pipe within the garden's interior. It is more conventional though to place the pipe line down the center of the garden and to support it at a height of about 3 ft. The advantage of the higher location has already been mentioned. However, it is easier to reach the line when nozzles become clogged or something else goes out of order, if it is supported at a lower height. Everything considered, the low-post installation is better for the home garden than the high-post. Although both the posts and pipe line can be removed rather easily, it is better to plan the installation so that they can remain in place the year round because, even under the best of circumstances, taking the pipe down or putting it up is the kind of nuisance task that nobody likes to do. The essential elements of such a system are the overhead pipe line, the nozzles, the union which permits turning of the entire pipe line, the supply riser, and the supports In making large installations, the pipe is usually purchased without the nozzles and is drilled and tapped to receive them just before installation. This is an inconvenient method for the small homeowner because special tools are necessary for drilling the holes and cutting the thread. Fortunately the manufacturers of supplies for this kind of irrigation system offer lengths of pipe with the nozzles already installed. The same manufacturers also supply the turning union, the pipe brackets, etc. A handy device which is not shown is a special hydraulic machine which is attached to the supply end of the pipe and is operated by water pressure in such a way that it slowly rotates the length of the pipe. In fact these motors can be arranged so that they rotate the pipe slowly in one direction, then reverse themselves and, slowly turning it back, continue the process until they are shut off. Also they can be arranged so that they will shut themselves off after a predetermined period of time. If you decide to use one of these motors, you will probably elect to place one line of pipe down the center of your garden rather than two lines at the sides, because one is required for each line of pipe; and they are not inexpensive.
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