The invention relates to an agricultural irrigation system consisting of a plurality of rotatable retractile sprinklers or water guns which are adapted to be submerged in covered pits when not in use, and to be projected out of these pits to a height above the plants in the field, during irrigation periods. The invention further relates to a method of actuating one or more sprinklers out of the total number installed in the field, from a central point servicing a larger number of irrigated areas.
Sprinkler irrigation of large planted areas is, up to date, carried out by different methods, each having its advantages and drawbacks, such as:
(1) Laying of a temporary system of pipe lines above ground with a plurality of sprinklers installed at predetermined intervals, and removing the pipes and sprinklers after the irrigation period, for the purpose of harvesting the produce and tilling the soil for the next crop. Although this method permits full use of the entire area for planting or sowing, it requires much manual work which is costly and time-consuming. In addition, it results in rapid wear and tear owing to rough handling and during storage.
(2) Laying a permanent system of underground pipe lines of aluminum or plastic with risers projecting above ground at predetermined intervals and mounting sprinklers onto the risers during each irrigation period. The sprinklers are removed during harvesting and soil tillage, in order not to be damaged by the agricultural machinery, and in order not to interfere with the work. In spite of the removal of the sprinklers, there remains a narrow strip along each pipe line and the risers, which cannot be utilized, since ploughing and tilling along these strips can lead to damage to both the piping and the agricultural implements.
(3) The same applies to an underground pipe system with permanently fixed sprinklers, with the additional drawback that the strips of non-workable soil are wider and that the danger of damage to the sprinklers is augmented.
(4) Mobile irrigation equipment of different design has been introduced lately and has found great acclaim, as for instance "Center-post" irrigation machinery, as well as ground-supported carriers advanced along an irrigation zone across a field. The great advantage of these machines is the possibility of using the entire area for tilling and planting, since there are no permanent obstacles to the passage of agricultural machines. Their main drawback is the high cost of the equipment, high maintenance costs and the requirement of constant supervision, in contradistinction to stationary irrigation equipment which can be fully automated.
In view of the aforesaid it is one object of the invention to instal a system of underground sprinklers or water guns which are completely covered during non-irrigation periods, so as to permit agricultural machinery to travel freely over the entire field area, thus making all areable land suitable for planting and sowing.
It is another object to permit the operation of only a limited number of sprinklers during a certain period, dependent on the available water flow, and of another set of sprinklers during the following period, signals for operation being given from a central point afar from the irrigated area.
It is still another object of the invention to permit full automation with regard to the opening and closing of individual sprinklers in accordance with the humidity of the soil or other factors, as signalled by tensiometers or other instruments.