Water Water deficit especially after heading is one of the most effective factors of wheat yield loss in Iran and across the world and identifying the physiological traits related to plant resilience is of great importance in screening for tolerant varieties. The objective of this study was to evaluate the variation in stem reserves accumulation capacity and its relationship with remobilization in some wheat cultivars. 22 wheat cultivars were cultivated in a split plot design with three replications, full irrigation and 40% of field capacity being main plots. The amount of accumulation and remobilization was estimated by measuring internodes weight and stem soluble carbohydrates content (WSC). Significant genotypic variation among cultivars was observed under both normal and drought conditions. Maximum accumulation was found in lower internodes followed by peduncle and penultimate using dry weight measurement method. In WSC measurement method, however, maximum accumulation was observed in penultimate followed by lower internodes and peduncle. Cultivars ranking based on accumulation was also different in two methods. Drought stress caused decline in internodes weight, WSC and yield and remobilization efficiency. The specific stem weight had the highest correlation with remobilization. Significant correlation was found between grain yield and remobilization, specific stem weight and WSC.

In order to calibrate and validate the CERES-wheat model, two experiments were carried out at Agricultural and Natural Resources Research Center of Khouzestan during 1382-83 and 1383-84 growing seasons. In addition, we used results of experiments, which were performed in previous years at this Research Center. The values of root mean square error (RMSE) for anthesis and maturity dates, grain yield and biomass production were 2.5d, 5d, 640 kg/ha and 460 kg/ha, respectively. These RMSE values were less than 10 percent of observed data means. The results indicated that the CERES-wheat model can satisfactorily predict phonological stages, grain yield and biomass of wheat. Then calibrated and validated CERES-wheat model can apply to research purposes in Ahvaz conditions.

Crop simulation models are increasingly used in agriculture. These models help in saving time and expenses. The objective of this study was to evaluate CropSyst model in predicting development, growth and yield of wheat cultivars from Golestan province. To do this, experimental data from different experiments were gathered for Kohdasht, Shiroodi, Tajan and Zagros. Model performance in simulating days to anthesis and maturity, biomass accumulation at anthesis and maturity and leaf area index at anthesis, nitrogen accumulation at anthesis and maturity and grain yield were evaluated. Root mean square error (RMSE) were 5.2 and 9.5 days for anthesis and maturity that were 4.6% and 6.4% of the means, respectively. RMSE of LAI at anthesis was 1.2 m2.m-2 that was 20.9% of the mean. For grain yield, RMSE was 556 kg.ha-1, 13.3% of mean. For other development and growth characteristics, model performance was acceptable. Therefore, this model can be used in simulation of these cultivars.

The present research has been conducted to parameterize and evaluate the APSIM-Wheat model for winter wheat and to use the model for evaluation of climate change effects on grain yield. The model is used to simulate leaf area index, dry matter, and grain yield of Roshan cultivar winter wheat in Karaj and Khomein regions between 2014 and 2015, under four irrigation regimes and three levels of nitrogen fertilizers. The experiments have been conducted in both regions as split-plot in a randomized complete block design. Irrigation is considered as main plot and nitrogen as a sub-plot. Model parameterization is based on observational data from full irrigation and 200 kg/ha nitrogen treatment in both regions. Results from the model evaluation show that the simulated values closely predict the observed values so that the RMSE in both regions is less than 670 and 450 kg/ha for biomass and yield, respectively, being below 0. 56 for leaf area index as well. Normalized RMSE in all treatments has been below 17. 8%, with Wilmot's index being above 0. 82. The evaluation of model shows high performance and its possible use in other studies. Results from climate change analysis show that increasing the temperature from 0 to 5 ° C leads to a maximum reduction of 75% in grain yield and an increase in carbon dioxide concentration, resulting in a maximum increase of 24% and, if the temperature increase exceeds three degrees Celsius, the grain yield will decrease in all possible concentrations of carbon dioxide.

The simulation models of yield response to water are expected to play an increasingly important role in the optimization of water productivity (WP) in agriculture. In this study, the CERES-Wheat model was used to simulate of wheat yield response under different irrigation-cultivar treatments with three irrigation treatments in main plots and Five wheat cultivars in sub plots consisted of C1:C-75-5, C2: C-78-4, C3:C-78-8, C4: C-79-6 and C5: C-79-16 in Mashhad region during the years of 2002-2003 and 2003-2004. According to the results, the relative root mean square error of grain yield simulation by CERES-Wheat model was 7 and 10 % for 2002-2003 and 2003-2004 years, respectively. Because the relative root mean square error was less than 10 percent, so done well simulation. Also, the root mean square error calculated for grain yield for both years was less than 10 percent of the observed mean. The results are indicating a good match to the simulation results of the model. The value water productivity based on crop evapotranspiration and irrigation water value in I3-C-79-6 treatment has the value highest for both years of 2002-2003 and 2003-2004. Therefore, the noted irrigation management (I3) and wheat cultivar (C-79-6) can be recommended in the study area. The overall findings of this study to confirm the optimal performance of the model CERES-Wheat in the growth process simulation and the water impact on yield in the study area.

This study was conducted during summer and winter of 2018- 2019 in the agricultural research field of Shahid Chamran University. Experimental design was split- plot based on RCBD with three replications. The main plot was the type of agricultural system in three levels including conventional (Conv), organic (Org) and sustainable (Sust) (integrated between Conv and Org) and sup- plot was the type of pre- cultivated crop in sequence with wheat including cultivation of mung bean (M- W), corn (C- W), sesame (S- W) and fallow (F- W). Yield quantity (yield and its component) and quality (grain protein), an estimate of photosynthesis matter transfer index of wheat and soil organic carbon (SOC) after one double-cropping were measured. The result showed that the highest (545.04 g/m2) and the lowest (409.28 g/m2) seed yields were obtained in Conv and Org respectively. In contract, with the changing type of system from Conv to Org, grain protein was increased significantly (from 8.3 to 9.6 %). In addition, the highest (535.47 g/m2) yield of wheat was obtained from M- W double cropping. On the other hands the highest remobilization and current photosynthesis matter were obtained in the organic agricultural system with M- W and conventional with M- W double cropping. The situation of SOC showed that the highest (33.18 mg/g) SOC was obtained in the organic agricultural system with C- W double cropping. The reason for improving SOC in the organic and sustainable agricultural system was application of organic matter (compost and vermicompost) and crop residue management. Totally, from the crop ecology point of view, sustainable agricultural method with a sequence of M- W was the most desirable system.

Food security is equal to yield stability. Fifty percent observed yield variability of irrigated wheat in Khorasan province indicates that these are no reliable food security. Crop growth simulation model as a quantitative tool based on scientific principles that could evaluate different climatic effects, soil, water and management factors on crop production. CERES-Wheat model is a widespread model, which has been employed in many studies across the world.To evaluate CERES-Wheat model in yield predication, two completely randomized Block Design experiments with four replications were conducted in two different climatic locations, using six cultivars released between 2001-2002 years. The experiments were carried out at Mashhad and Birjand agricultural research stations. Genotype coefficient and cultivars differences were determined using GENCALC software. To evaluated the yield, Root Mean Square Error (RMSE) was calculated and formed to be 44.44 and 62.7 Kg/ha for Mashhad and Birjand trails respectively this was less than 10% of observation mean as a model accuracy. Because of agricultural complexity, it was difficult to have access to input data, and unknown physiological properties, specially interaction under different condition and environments cause discrepancy in model simulations thus indicating that model validation and calibration is necessary before applying the model in any future application as a research tool.

Crop growth simulation models simulate crop growth and development basis of underlying processes such as photosynthesis, respiration with due consideration of the environmental effects on these processes. The objective of this research was the evaluation of CERES-Wheat model simulation of different growth parameters as well as wheat phasic development prediction as compared with field experiment observations. To facilitate determination of the genotype coefficients, CENCALC software is used to the realization of cultivar differences. To evaluate the phenological results Root Mean Square Error (RMSE) was calculated which was zero for flowering in both experiments with RMSE for physiological maturity being 6.5 and 7.49 days for Mashhad and Birjand trials respectively. This was less than 10% of observation mean as a model accuracy. Biomass production time course was simulated accurately, however it overestimated the total biomass. It seems that the main cause in biomass overestimation is the constant parameter in the model equations not being changeable by the user as well as these values differing from our observations.

Wheat (Triticum aestivum L. ) as one of the most important agronomic crops has a special status in Iran. Reducing the yield gap is one of the ways to raise the production. In order to, the production rate and thewheat yield gap in Golestan province were analyzed by using a simple simulation model SSM– Wheatand GIS software. For this purpose, the managerial information of wheat farming and cultivation werecollected based on the provincial level and with regards to the information of 25 weather station and theregion soil information, the potential yield was simulated in the irrigated and rainfed conditions at theprovincial level and then the potential yield zoning was performed in the GIS and then with regards to thefarmer's production rate and real yield at the provincial level, the yield gap and the production one werealso calculated in the irrigated and rainfed conditions. Results indicated that the yield average of irrigatedand rainfed potential with regards to the figures and current agricultural methods are respectively 8. 140and 4. 930 kg per hectare. Also, the potential production in the irrigated and rainfed conditions wasobtained equal to 1. 357 and 1. 112 million tons (total 2. 469 million tons). Results showed that in case ofstudying and removing the factors which may cause the yield gap in the said province, the wheatproduction can be increased from the current 926 thousand tons to 1. 975 million tons. Based on theresults of Golestan province, the most important factors causing wheat yield vacuum with currentcultivars and agronomic management, improper irrigation management, improper cultivation of cultivarsand inappropriate use of basic fertilizers, road and low fertilizer, and for eliminating yield vacuum, use of165 to 215 kg of seed per hectare, using certified seeds of suitable cultivars for water and dry farming, consuming at least 50 kg of phosphorus fertilizer (equivalent to P2O5) during cultivation, consuming atleast 95 kg of pure nitrogen per hectare and integrating farms are suggested.

Wheat ground beetle Zabrus tenebrioides (Goeze) (Coleoptera: Carabidae) is an important wheat pest in Iran and some regions of the world. This pest causes damage to wheat by feeding on the root, stalk, and leaves. Farmers try to control this pest by the foliar application of different insecticides, but this method causes damage to the environment. To find an effective method to control this pest, the thiamethoxam insecticide (Cruiser®) efficiency was evaluated using seed treatment in this study. An experiment based on a randomized complete block design with four treatments and four replications was conducted in a field in Ramhormoz city, Khuzestan province (Iran). The treatments were 150 and 200 ml of thiamethoxam plus 2350 ml of water for seed treatment, 2,000 ppm of diazinon by field spraying at the wheat tillering stage, and a control. The results indicated that the average plant density in 150 and 200 ml of thiamethoxam (333.58 and 333.28 plant/m2, respectively) was more than those of diazinon (258.28 plant/m2) and the control (182.12 plant/m2). The average ear density in 150 and 200 ml of thiamethoxam (513.78 and 506.12 plant/m2, respectively) was more than those of diazinon (321.22 plant/m2) and the control (260.86 plant/m2). According to the present results, farmers can use 150 ml of thiamethoxam plus 2350 ml of water for 100 kg of seeds to control this pest by seed treatment.