Introducing and evaluation of relative economic water productivity index

In the agricultural sector, indicators of physical productivity (WPPa), economic productivity (WPEa), physical (WPGp) and economic productivity gap (WPGe) of water are used to evaluate the performance of farmers and gardeners. The WPPa index, does not consider the price and costs of the product. The WPEa index is not only affected by inflation and market regulation policy, but also does not take into account the effect of the region's soil and climate. The WPGP and WPGe indices do not provide an accurate evaluation of water productivity of plants due to the difference in the nature of the performance of different plants. Purpose: In this study a new index is introduced that does not have any the aforementioned disadvantages.Material and method: A relative economic water productivity index was introduced and evaluated using different data for each of the factors affecting agricultural production, including soil, plant, climate, management and inflation, and it was compared with the WPPa, WPEa, WPGP and WPGe indices. Results: The results showed that unlike other indicators, the relative economic water productivity index evaluated water productivity in different plants compared to other indicators in proportion to the production capacity of the soil and the climate of the region for any type of agricultural management without being affected by the different nature of crop plants performance and inflation (economy). Because in the KWPe index, the water productivity of each plant is estimated based on the potential conditions and these conditions are unique for each plant and in each region and climate and under each agricultural management, therefore, the productivity of different plants in different regions can be compared only with this index. So that the WPGe index estimated the average value of water productivity for wheat and barley in different soils to be equal (3973 toman/m3), but the KWPe index estimated water productivity of wheat and barley at 0.67 and 0.33, respectively. Also, the KWPp index estimated the same value for water productivity of wheat and corn as 0.42, but the KWPe index estimated 0.36 and 0.4 for wheat and corn respectively due to the high price of corn compared to wheat.