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Abstract: In the agricultural production process of Iran, water is the most limiting and important input for food production. Therefore, increasing the productivity of water use, especially in the crop production sector, is essential as a key indicator for evaluating agricultural water management. To determine the relative advantage of crops in terms of water productivity, it is appropriate to use the yield per unit volume of water (CPD), the benifit per unit volume of water (BPD) and the net benifit per unit volume of water (NBPD) indices. However, these indices do not separate the constraints of land and management resources and do not easily become a prescription or guideline for improving productivity at the farm, network and plain levels. The use of the newly introduced series of indicators including potential climatic water productivity (PCWP), potential land water productivity (PLWP), actual water productivity (AWP), water productivity gap (WPG), water productivity management index (WPMI), and water productivity management level (WPML) can separate the contribution of qualitative and quantitative constraints of basic inputs and the contribution of management in the water productivity index and has a great advantage over the usual indicators mentioned above. Therefore, in this study, the PCWP, PLWP, AWP, WPG, WPMI, and WPML indices were investigated and determined for three corn fields with different management in the irrigation and drainage network of Moghan, which is one of the main poles of corn production in the country, in the 1394-95 crop year. PCWP ranged from 31 to 46 in farms 1 and 3 and PLWP ranged from 26 to 42 kg/m3 in farms 2 and 3. AWP was always lower than PLWP and affected by farm management on yield amount and proportionality of water allocation and consumption with actual yield and in the best conditions it was 27, 24 and 39 kg/m3 for farms 1, 2 and 3. In conditions of water allocation proportional to the crop calendar and actual production and in a location-specific manner, WPG decreased sharply and was 0.2, 2.2 and 3.5 kg/m3 for farms 1, 2 and 3. One of the important factors affecting the potential of climatic water productivity (PCWP), which is an important index for quantifying the effectiveness of intrinsic factors on physical productivity, was crop calendar. PCWP index was investigated for eight crop calendars and three forage maize farms. For fodder corn, the average PCWP in the second crop increased by 23% compared to the first crop, and from the perspective of improving water productivity, second cropping calendars are recommended. Considering the changes in water productivity (WP) and its components, it is necessary to allocate water and plan irrigation based on plant evapotranspiration in standard conditions (ETc) and in accordance with the crop calendar. For proper comparison and analysis in selecting a crop calendar, using WP based on ETc and actual yield is not appropriate, and it is necessary to use PCWP values based on climatic production potential (CPP) in water conditions (IPP) and ETc. For farms 1, 2, and 3, the PCWP and PLWP indices were 31, 32, and 46, and 27, 26, and 42. This indicates the difference in crop calendar and soil conditions of the two farms, given the same climate of the farms. The AWP index varied depending on the management level in farms 1, 2 and 3, respectively, from a minimum of 9, 7 and 6 for actual irrigation water conditions to a maximum of 27, 24 and 39 kg/m3 for water allocation conditions equal to the actual plant requirement in proportion to production, which is 3, 3.5 and 6.5 times higher than the current conditions of the farms. In practice, the AWP index alone cannot be used to judge, analyze, and compare the management status in different situations. The Water Productivity Management Index (WPMI) in 3 farms showed that overall management in Farm 1 was better than in Farm 2 and 3. The main reason for the decrease in the index and level of water productivity management in Farm 1 was high water consumption, in Farm 2 low yield, and in Farm 3 a combination of the two. In general, the results showed that the PCWP, PLWP, AWP, WPG, WPMI, and WPML indicators are useful as key indicators for evaluating and improving agricultural water management. These indicators on a macro scale can be the basis for policy-making and essential decisions on how to manage the distribution and consumption of inputs and improve water productivity in the agricultural sector. These indicators on a micro scale are used to evaluate the current situation and improve water productivity, especially with the implementation of special management - water location and other inputs, in the agricultural production process. Since these indicators can be measured and expressed quantitatively, the conditions are available for their monitoring, evaluation, target setting, and improvement to be manageable. Therefore, it is suggested that they be considered in all studies and research on water productivity in agricultural production.
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