چكيده انگليسي :
The climate in Isfahan province varies greatly from west to east. Different regions have unique characteristics such as water quality, soil texture, organic matter, topography, and elevation above sea level. The combination of these factors causes the yield of winter wheat and barley to be different in each region of the province. Therefore, it is necessary to consider what areas, at what time and under what management of water and nitrogen fertilizer should we cultivate each of these products in order to achieve the maximum yield as well as reducing water consumption and preserve the environment. In the upstream areas of the Zayandeh Rood basin (UZRB), due to the excessive use of nitrogen fertilizers and the failure to match the fertilizer consumption with the plant's needs, improper irrigation and lack of attention to the impact of rainfall patterns, the water resources are polluted. The main focus of this research is on the comprehensive management of water and especially fertilizer in UZRB, however, in order to make the research more comprehensive and practical, the potential of wheat and barley production in the ZRB was also investigated. The experimental treatments of wheat and barley including three levels of nitrogen: 50 kg N ha-1 (N1), 100 kg N ha-1(N2) and 200 kg N ha-1 (N3), as well as two levels of irrigation, defficit irrigation (I1) and full irrigation (I2) were implemented in the experimental site in a completely randomized design. The CERES-Wheat model and CERES-Barley models were meticulously calibrated and evaluated over three years, involving an experimental field and farmer fields. The calibrated model simulated 25 N fertilizer scenarios, spanning various N levels (50-250 kg ha-1) and split patterns. This considered soil textures and meteorological data.The model's outcomes, yield (Y), water productivity (WP), irrigation water productivity (IWP), N residual in soil (NR), N leaching (NL), available N use efficiency (ANUE), N absorption efficiency (NAE), and N utilization efficiency (NUE), were categorized into four distinct groups based on the Palmer's Drought Severity Index (PDSI). Indices underwent thorough Principal Component Analysis (PCA) to identify the optimal scenario. Also, in order to determine the best planting date and yield potential in UZBR, calibrated coefficients were used. And at the basin level, the genetic coefficients of previous researches were used. The deficit irrigation in UZBR increased the IWP for wheat and barley by 55% and 83%, respectively. The usage of 100 kg N ha-1 instead of the current 200 kg N ha-1 reduced wheat and barley yields by 11.7 and 14.5%, respectively. On the other hand, nitrogen losses are reduced by 56.6 and 66.1%, respectively. In general, the usage of nitrogen fertilizer at the rate of 150 kg ha-1 in the UZRB is recommended as an optimal amount both in terms of increasing yield and preserving the environment. According to the results, suitable planting date was obtained as following: for Fereydan, Fereydunshahr and Chadegan regions 26 September to 15 October, Khansar and Tiran 26 September to 25 October, Golpayegan 5 October to 5 November, Lenjanat, Najafabad, Kabutarabad and Varzaneh 15 October to 25 November. In unrestricted condition, the average production potential of wheat and barley at the basin level was 11914±443 and 7833.50±509.85 kg ha-1, respectively, and WP potential was 1.73±0.11 and 1.51±0.1, respectively. The IWP of wheat and barley was 16.3% and 13.3% higher for the western than the eastern regions, respectively. If we consider the limitation of salinity of water sources, on average, in the eastern areas of the basin, we observed 27.49 and 13.45 percent yield reduction in wheat and barley, respectively. The portion of green water in the production of wheat and barley for the northwest, the west, middle and the east of ZRB were 41.29, 42.06, 26.21 and 15.03 percent, respectively
