Estimation of Wheat Irrigation Water by Inverse Solution Method of the Production Functions under Water Stress Conditions Using NIAZAB System

Different factors are effective in increasing wheat production, one of the most important of which is water. Determining the actual consumed water of wheat in arid and semi-arid regions is of particular importance and the economic use of water is a serious and very important issue for farmers and researchers who cultivate and produce wheat under irrigation. The season of wheat cultivation has a direct effect on its water requirement due to the change in the energy pattern affecting evapotranspiration, and it will definitely have a lower water requirement in winter than in spring and summer. Therefore, the present study was conducted in order to investigate the water requirement system in determining the actual amount of irrigation water and wheat plant yield based on the inverse solution of the production function under water stress conditions for Alvand variety wheat in Qazvin province.

The research was conducted in 2017-2019 crop years in Qazvin province on a land of 600 square meters in Esmailabad research station (49º 52' N, 36º 15' E, 1285 MSL). The experimental design was in the form of split plots and in the form of a randomized complete block design with three replications. So that the main factor of irrigation management includes providing water requirements of 20 (I1), 40 (I2), 60 (I3), 80 (I4) and 100 percent (I5) and secondary treatment includes irrigation until the end of the flowering stage (S1) and The pulping of the seed was (S2). The country's using NIAZAB system was provided by the Soil and Water Research Institute (SWRI). This system is designed to determine the water requirement of farmland and Orchard products, which has the ability to estimate and determine the water requirement, Consumed water and plants irrigation planning at the level of the region, city, catchment and plain. One of the prominent points of this system is its location-based nature, and the user can extract their regional needs by referring to the system and can allocate the water used for the cultivation pattern under different usage options to the beneficiaries of the agricultural water stakeholder with the ability to provide an update.

The results showed that the root mean square error in Tafteh, Pasquale and Raes methods was 122, 83 and 126 mm per day, respectively, and Pasquale method had a better estimation than other methods. In Pasquale's method, the best normalized root mean square error was observed with 0.18%. The index of agreement or consistency in Tafteh, Pasquale and Raes methods was 0.95, 0.98 and 0.95%, respectively, and the Coefficient of Efficiency of the model was 0.77, 0.91 and 0.73, respectively. The results of the statistical analysis showed that the measured and simulated values are close to the 1:1 line and have a good relationship, and the coefficient of determination values in the studied years showed 0.98. The results of estimation the amount of wheat plant evapotranspiration in the using NIAZAB system in the Qazvin plain with the methods of Tafteh et al. (2013), Pasquale et al. (2017) and Raes et al. (R2=0.98) were high and the root mean square error in Tafteh, Pasquale and Raes methods was 120, 83 and 126 mm per day, respectively, in which Pasquale's method had a better estimation than other methods.

In general and according to the statistical results, a good approximation was observed between the real data and the using NIAZAB system in determining the amount of irrigation water under water stress conditions, which indicates the appropriate evaluation of the water requirement system and the ability to simulate the wheat yield function in relation to different treatments. It was irrigation and this system can be used as a suitable tool in estimating water needs to improve water management in wheat.