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Acceptable value of microirrigation system uniformity

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  131690789,  2013 Kansas City, Missouri, July 21 - July 24, 2013. (doi: @2013
Authors:   Jian Wang, Delan Zhu, Lin Zhang
Keywords:   microirrigation uniformity yield optimization method numerical simulation

Abstract. A forward step method was proposed for hydraulic analysis of microirrigation pipe netwoks. With considerations of manufacturer and microtopography variation, Christiansen unifromity coefficient (Cu) could be calculated. This method was used to modify microirrigation design criteria applicable to different soil and crop situation. Combining crop-water production function, relationship between irrigation water amount and yield (Y) was analyzed when the network system was given, meanwhile, system annual investment (CT) could be determined. Consequntly, the uniformity and yield-cost ratio (Y/ CT) for different subunits were obtained through numerical simulation. Moreover, an optimization method for micro-irrigation uniformity for different plants was developed, using uniformity as decision variable and maximum yield-cost ratio as objective. Taking watermelon as example, regression analysis results showed that the relationship between yield-cost ratio and uniformity coefficient observed to a quadratic function and the optimized acceptable uniformity (Cu) was 0.78. A tiny increase in uniformity would cause a sharp decline of yield-cost ratio when it was beyond the range of reasonable values. When uniformity (Cu) increased from 0.83 to 0.93, the yield-cost ratio (Y/ CT) would decrease by 58.57%. Therefore, blind pursuit of high irrigation uniformity was not reasonable in micro-irrigation design since unnecessary the economic loss would be caused.

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