An expert system to select farm and field set sprinkler systems and to determine the effect of UCC on the cost of set sprinkler systems

An expert system called SPRINKLEXP was created to select farm and field sprinkler set systems for operation on level fields of a monocultural or simple polycultural cropping system. It permits not only a preselection of the set systems as a function of criteria imposed by diverse components of the farm crop production system and by the technological and economic environment of the farm, but also the study of the effects of the variation in the design irrigation uniformity, measured by the Christiansen coefficient of Uniformity (UCC), and the effects the sprinkler spacings may have on system capital cost. The final selection of a set sprinkler system in the expert system is based upon an additional criterion of economic optimization, which may optionally embed the formalized effects of UCC and sprinkler spacing on the initial capital cost of the system.; SPRINKLEXP was applied to irrigated spring wheat in the USA and to three sprinkler set systems (hand move, wheel line, and fixed set) with two objectives: study the effects of UCC and sprinkler spacing on the system initial capital cost, and minimize the initial capital cost. For the three set systems, it was found that as UCC increases from 0.60 to 0.92, the system initial capital cost abruptly decreases for all sprinkler spacings and most irrigated areas at a particular value of UCC, which is designated by the acronym UCP. At UCP, the required number of operating laterals or machines per set decreases by at least one unit due to the shortening of the set time and to the consequent increase in the number of irrigation sets per day. This UCP value depends upon the average design application rate (A_p) and the management allowable deficit (MAD). At a constant value of MAD, it is inversely proportional to A_p. Envelope curves of maximum initial capital cost were developed as linear regression equations between the system initial capital cost and the irrigated area for each sprinkler spacing, and for two ranges of UCC values. Two indices were also created to assess the comparative cost stability of each of the three set systems as UCC increases.