Investigation of the Effect of Crop Calendar on the Potential Climatic Water Productivity (PCWP) of Maize in Moghan Plain

The Potential Climatic Water Productivity (PCWP) is an important indicator to quantify the effect of intrinsic factors on physical water productivity. The crop calendar is one of the important factors affecting this index. Considering the importance of maize farming and the necessity of improving water productivity, PCWP index has been investigated for eight agronomic calendars and five maize farms between 2015 and 2016. Crop calendars were extracted from available official sources and expert meetings. The PCWP components are determined from the FAO Growth Model (yield) and the standard FAO Penman-Monteith method (evapotranspiration). The mean PCWP for maize forage in the second crop cultivation has increased by 23%, compared to the first cultivation; therefore, the use of second cultivation calendars is recommended in regard to the promoting water productivity. In spite of a 13.7% increase in PCWP in the second maize-grain cultivation, the use of the first cultivation calendars is recommended. Due to changes in water productivity (WP) and its components, water allocation and irrigation scheduling based on ETc appropriate to the crop calendar is essential. However, WP based ETc and actual yield are not appropriate for correct comparison, analysis, and crop calendar selection, so it is necessary to use PCWP values based on climatic potential production (CPP) under water conditions (IPP) and ETc.