افشبن سلطانی

water over-withdrawal in Iran is like a cancer that has taken root in the country's nature and is making its conditions difficult every day. Therefore, planning and effective measures must be taken at the country level to reduce this over- withdrawal. For this purpose, in the present study, it was assumed that withdrawal water for agriculture in the country would decrease from 86 billion m3 per year to 62 billion m3 per year (the allocable volume of water for agriculture as announced by the Ministry of Energy). Then, using linear programming, the current cropping pattern was optimized with the aim of maximizing farmers' income. In this study, information on the cultivated area, yield per unit area, price and production cost (2013-2017) of more than 30 important plant species was collected separately for each province of the country. To estimate the irrigation water volumes under farmers’ conditions, a crop simulation model (SSM-iCrop2) was used, which has been tested and set up to simulate the growth, yield and field water balance for more than 30 plant species throughout the country. The economic mathematical programming model was solved using LINGO software. The results showed that reducing water withdrawal from 86 to 62 billion m3 per year without changing the cropping pattern would cause the country's irrigated area to decrease by 29 percent (from 8,409 to 5,949 thousand hectares) and farmers' income would also decrease by 30 percent (from 173 to 121 thousand billion rials). However, the optimization of the cropping pattern resulted in an 18% reduction in the cultivated area (from 8,409 to 6,907 thousand hectares) and an increase in farmers' income by 9% (from 173 to 190 thousand billion rials); that is, while water withdrawal decreased by 28%, farmers' income not only did not decrease but also increased with the optimization of the cropping pattern. The optimized cropping pattern also created significant savings in fertilizer and energy consumption, which is of great importance in conditions of limited energy resources. The most important changes in the optimized cropping pattern were the increase in the cultivated area and production of potato and summer vegetables (104 and 76 percent more than the country's needs, respectively) that must be exported, and the decrease in the cultivated area, production, and consequently increased dependence on imports in sugar-beet, barley, silage corn, and alfalfa. In the optimized cropping pattern, high dependency (more than 50%) to import of oilseeds, grain corn, and meal will continue as in the current conditions (current cropping pattern). Optimization of the cropping pattern makes it possible to reduce water withdrawal to the level that the Ministry of Energy without reducing farmers' income. However, there will still be some reduction in the area under irrigated cultivation and, as a result, a decrease in the self-sufficiency of some crops. Thus, the expectations of the country's crop production capacity must be rationalized and reduced.

The canola plant (Brassica napus L.), containing 40 to 44 percent oil, is considered one of the most important edible oilseeds and is the third most significant annual oilseed crop in the world after soybean and oil palm. The global demand for food is rapidly increasing due to the growing population. This demand is expected to rise by 60 percent by the year 2050, which poses a significant challenge, especially in the context of climate change. Human activities since the industrialization era have led to an increase in greenhouse gas emissions, which are expected to alter regional rainfall patterns and temperatures. The most critical feature of global climate change is the significant increase in temperature and uneven distribution of precipitation, which are limiting factors for sustainable development. The ultimate goal of assessing climate change risks is to identify adaptation strategies to achieve sustainable development in a specific region. Adaptation strategies vary depending on agricultural systems, regions, and climate change scenarios. The aim of this study is to examine adaptation strategies to enhance drought resistance in rapeseed plants concerning future climate conditions in the country.

The present study aims to predict the impact of climate change on the growth and development of rainfed canola in Iran using two general circulation models, HadGEM2-ES and IPSL-CM5A-MR, derived from the CMIP5 project under two emission scenarios, RCP4.5 and RCP8.5, as reported in the fifth assessment report of the IPCC for the future period from 2040 to 2069. The downscaling of climatic parameters generating weather data was conducted using climate scenario generation tools within the AgMIP project and implemented in R software. After simulating the future climate and producing the necessary parameters (minimum temperature, maximum temperature, precipitation, and solar radiation), the growth and development simulation of rainfed canola was carried out using the SSM-iCrop2 model under current and future climate conditions. Additionally, the results of the growth and development simulation of rainfed canola under future climatic conditions in Iran were evaluated with increased drought resistance.

The results indicated that the average temperature during the canola growing season in the future is expected to increase by an average of 2.3 degrees Celsius for the RCP4.5 emission scenario and by 3.1 degrees Celsius for the RCP8.5 scenario compared to current conditions. Additionally, the results showed that the distribution of precipitation among the growth seasons would vary between the two models. The simulation results under climate change for both RCP4.5 and RCP8.5 scenarios revealed that, with the increase in average temperature, the length of the growing season would decrease in both models studied. However, it is predicted that water productivity will increase under both emission scenarios. It is anticipated that the average yield of canola in the country in its main cultivation areas will increase by 5% and 8% under the RCP4.5 and RCP8.5 scenarios, respectively, compared to current conditions. By implementing adaptation strategies to enhance drought resistance, it is expected that under both RCP4.5 and RCP8.5 scenarios, the average yield changes will increase by 8% and 9%, respectively, compared to a future without adaptation strategies.

The results of this study indicate that, on average, the yield in most of the main canola cultivation areas in the country is expected to increase under both emission scenarios. By implementing adaptation strategies to enhance drought resistance in the future climate, it is predicted that the average yield will increase compared to a future without adaptation strategies.

Common bean (Phaseolus vulgaris L.) due to its high nutritional value has an effective role in ensuring food security of the community. In Iran, protein supply is mainly dependent on plant products, and any action to improve the yield and production of protein-rich crops, which are headed by legumes, is of particular importance. Increasing yields by optimizing production management and eliminating yield gaps is the most appropriate way to increase crop production and improve food security. Therefore, accurate estimation of potential yield and yield gap and crop production is essential for sustainable food supply. The present study aims to estimate the yield gap and production and water productivity of bean in its main climate zones in Iran based on the Global Yield Gaps Atlas (GYGA) project at the Gorgan University of Agricultural Sciences and Natural Resources was done in 2016. In order to estimate the beans yield gap and water productivity in Iran according to GYGA protocol, first the data related to farmers' yield (Ya) and bean harvested areas and production in the country in a period of 15 years from 2001 to 2015 from the Ministry of Agriculture of Iran was prepared. Then the distribution map of beans in the country was prepared. By combining the distribution map of the bean harvested areas and the climatic zoning map of the country, the main climatic zones (DCZs) of bean production were identified. Then, reference weather stations (RWSs) were selected according to the level of each climatic zone. In order to estimate the potential yield (Yp) and water productivity (Wp) based on weather data and major soil type and agronomic management meteorological in each of the selected areas, the SSM-iCrop2 simulation model was used, which was locally calibrated and evaluated. Finally, the bean yield gap (Yg) was calculated from the difference between the potential and actual yield of each RWSs was upscaled to DCZs and country-level. The results of comparing the average of beans actual yield reported by the Ministry of Agriculture of Iran with the actual yield calculated according to the GYGA protocol for the country with RMSE, CV and r values of 84 kg ha-1, 4% and 0.96 respectively, which indicated using This protocol can estimate the average yield of bean in the country with high accuracy. The average beans actual yield in Iran during the years 2001 to 2015 varied between 1.6 and 2.3 ton ha-1. Also, the average actual yield in the main climatic zones of production was 1.9 and between 1.1 (climatic zone 4202 in Germi) to 2.3 ton ha-1 (in climatic zone 3003 in Avaj). Bean potential yield was estimated from 3.4 (in climate zone 4202 in Germi) to 5.4 ton ha-1 (in climate zone 4103 in Hamedan and Bijar) with an average of 4.5 ton ha-1. Based on results, in the main climatic zones of bean production in Iran, there is a yield gap of 1.8 to 3.5 (average 2.6) ton ha-1, equivalent to 46 to 67% (average 57%). The average water productivity potential for bean in Iran was estimated to be 0.76 kg m-3. According to the results, if the factors causing the yield gap are eliminated by optimizing the management of bean production and cultivation and bringing the yield of bean fields to attainable yield (80% of potential yield), is increasing grain yield from the current value of 1.9 to 3.6 ton ha-1 with the same harvested areas, bean production in Iran will increase from the current 222,705 to 415,822 ton, which is equivalent to 46% increase in production and is considered an important step in improving food security.

Increasing water and soil salinity and the damage caused by it on plant products make it necessary to investigate the effects of salinity on crop plants. Studying the physiological traits changes under stress conditions is a suitable method for identifying the factors that affect crop tolerance to salinity stress and selecting tolerant cultivars.

A factorial experiment was conducted based on a randomized complete block design with three replications in the research greenhouse of the faculty of Plant Production, Gorgan University of Agricultural Sciences and Natural. Experiment factors included the applying four salinity levels with Hoagland solution (no application of salinity as control, application of 30, 60, and 80 mM NaCl) and different soybean cultivars (Hill, LBK, BP, Hog, Deer, Gorgan 3, Sahr, Hobbit, Williams, JK, and LWK). In this experiment, soybean seeds were inoculated with Rhizobium japonicum bacteria and planted in pots containing sand. The irrigation was done by distilled water from the planting until the appearance of the main leaf, and after that, Hoagland's solution (without nitrogen) continued. Seedlings were harvested after 60 days and Na+ and K+ percentage, Na+/K+ ratio, proline, nitrogen percentage, nitrogen yield, and total dry weight were measured. Analysis of variance and comparison of the means (LSD test) was done by the SAS software (version 9).

The results show that with increasing the salinity, sodium percentage, Na+/K+ ratio, and proline amount increased and total dry weight, potassium percentage, and nitrogen yield decreased. Deer cultivar with the highest percentage of nitrogen at the levels of 0, 30, 60, and mM NaCl and the lowest percentage of nitrogen reduction (28%) have the lowest total dry weight reduction (54%) from the control treatment to the 80 mM treatment. Hag cultivar have the lowest increase in sodium percentage and the lowest percentage decrease in potassium absorption and the lowest Na+/K+ ratio compared to other varieties. LWK, LBK, and Sahar cultivars had the lowest tolerance to salinity with the highest amount of sodium accumulation, the highest Na+/K+ ratio, and low production of proline, and dry matter. The results of correlation coefficients showed that there was the most positive and significant correlation between total dry weight and potassium percentage (0.904**) and nitrogen percentage (0.902**).

According to the obtained results, it seems that the tolerant cultivars deal with salinity stress with mechanisms such as more potassium absorption and osmotic potential regulation. Among the investigated cultivars and according to the measured indicators, the Deer cultivar was recognized as a tolerant cultivar and can be used for cultivation in saline lands and the Hag cultivar can be used in breeding programs.

Environmental stresses are always one of the most important factors in reducing the crops yield and production. When plants encountered with flooding stress, the concentration of active oxygen species increases. Increasing these compounds can damage to several cellular metabolic responses, such as Membrane integrity, photosynthesis and photosystem II efficacy. Following these events, early leaf aging and leaf area reduction may result in the loss of carbon fixation in the plant. Plants, in order to Confront with activated oxygen species, produce antioxidants, which reduces the effects of stress. Accordingly, this research was carried out to investigate the effects of flooding stress during tillering and stem elongation in two Koohdasht and Morvarid wheat cultivars on the content of antioxidant enzymes, photosynthetic pigments and their relationship with grain yield.

To conduct this research, a factorial experiment was conducted in a completely randomized design at Gorgan University of Agricultural Sciences and Natural Resources in two years, 1394 and 1395. The experimental treatments consisted of the length of the stress period at five levels (0, 7, 14, 21 and 28 days) as the first factor, the time of flooding based on the development stage of wheat (tillering and stem elongation) as the second factor and cultivar (Koohdasht and Morvarid) were considered as the third factor. In order to apply flood stress, the pots for each treatment were somehow placed in a water-filled pond that plants stem at a height of 2 cm was below the water. After applying stress treatments, traits such as content of catalase and superoxide dismutase enzymes, ascorbic acid, chlorophyll a, chlorophyll b, cartenoied and grain yield were measured. Also, linear models were used to describe the relationships between measured traits and flooding duration.

The results of this study showed that the damages of flooding stress in wheat depend on the time of plant placement under stress, the developing stage that stress associated with it, and the type of cultivar. In general, in this study, with increasing flooding duration, traits such as content of catalase and superoxide dismutase enzymes as well as ascorbic acid content increased significantly (linearly), but the amount of photosynthetic pigments (linearly) decreased significantly. On the other hand, the rate of increase of catalase and superoxide dismutase enzymes in Koohdasht was more than Morvarid. Also, the reduction of chlorophyll a and chlorophyll b in Morvarid was higher than in Koohdasht, but the reduction of cartenoied in Koohdasht was higher than in Morvarid cultivars. Finally, with increasing the duration of flooding period, the grain yield of Koohdasht and Morvarid cultivars decreased by 3.67 and 3.20 percent per day, respectively. In both cultivars, flood stress during stem elongation stage decreased seed yield significantly more than the tillering stage.

Flooding stress has a very important role in reducing wheat grain yield. In this regard, the duration of the stress period was the most important factor affecting the yield, and then the developmental stage where the stress occurred during it and the cultivar were ranked second and third, respectively. Increased content of catalase and superoxide dismutase enzymes was associated with reducing the grain yield, as the production of these enzymes occured in response to increased active oxygen species (oxidative stress) during the flooding. Reduce the content of photosynthetic pigments also means a reduction in plant photosynthetic capacity during flooding stress. The total of these changes led to a linear decrease in grain yield in both cultivars and both developmental stages. The more severe reduction in grain yield, when flooding occurred at the stem elongation stage, indicates the greater sensitivity of this developmental stage to stress.

Nowadays, climatologists and researchers are interested in the long-term forecast of climatic variables to be informed about the extent of their variations and to take measures to mitigate the adverse effects of climate change. Accordingly, general circulation models (GCMs) of atmosphere have been developed to predict climatic parameters. LARS-WG is a model to downscale the output of GCMs. It was used in the present research to generate data of daily precipitation, radiation, and minimum and maximum temperature across the cotton cultivation climatic zones (Meteorological stations) in Iran. The objective of this study is to estimate climatic factors (rainfall, radiation and minimum and maximum temperature) in the future period in major climatic cotton cultivation areas in Iran, which may be used for optimized water resource preservation and management in these regions. Also, the 5th IPCC report was used in this study, in contrast with the majority of investigations that use the 4th report.

In this research, the important areas under cotton cultivation in Iran are the target area. The data of 23 synoptic stations were used in these areas. The required meteorological data recorded in the stations were daily rainfall, minimum temperature, maximum temperature and sunshine. The present study assessed the performance of five different GCM models in simulating the data of precipitation, radiation, minimum temperature, and maximum temperature in nine synoptic stations (SABZEVAR, GHOOCHAN, GHOM, HASHMABAD, LAR, BILESOWAR, EDAREGORGAN, HASANABADEDARAB, and MASHHAD) from 2011 to 2016, firstly. Finally, two GCMs (MIROC5 and GFDL-CM3) were selected for the research purpose based on the results of t-test, F-test, and the Kolmogorov-Smirnov non-parametric test. Then, the parameters were predicted by the selected GCM models for 20 years (2041-2060) under the emission scenarios of RCP4.5 and RCP8.5.

According to employing the scenarios of RCP4.5 and RCP8.5, the predicted solar radiation does not show a significant change in the future period versus the base period of 1981-2010 in all studied regions based on both GCM models. The highest change (0.249 MJ / m2 / day) is based on the MIROC5 model and the RCP8.5 scenario in climate zone 6102 (HASHMABAD station). The predictions revealed that the parameters of maximum and minimum temperature would be ascending for all the climatic regions over the future period. The highest variations in the average long-term annual minimum and maximum temperatures versus the base period would be 2.67 and 2.75°C happening in Climatic Region 6002 Includes stations (HASANABADEDARAB, KHAF, HAJI ABAD and GONBAD) over the 2041-2060 period under Scenario RCP8.5. For both scenarios RCP4.5 and RCP8.5, the highest temperature increase was observed in the climatic zones where located in south of Alborz and the east of Zagros mountain chains as well as the Central Iranian Dry Plateau and the lowest increasing was in the climatic regions located around the Caspian Sea, the Persian Gulf and the south of Iran. For the total annual precipitation over the future period (2041-2060), the highest amplification was predicted by MIROC5 to be 98.5 mm under Scenario RCP4.5 in Climatic Region 6202 (EDAREGORGAN station), and the greatest loss of precipitation was predicted by the same model to be -29.8 mm in Scenario RCP8.5 in Climatic Region 6102.

Given the prediction of rising average annual minimum and maximum temperature and the decline of precipitation over the future period (2041-2060) in the climatic regions leading to the arid plain of central and southern Iran, it can be concluded that the variations of meteorological parameters induced by climate change will be significant in the cotton-growing climatic regions of Iran over the future decades.

Barley (Hordeum vulgare. L) is well adapted to drought and saline conditions as the most important limiting factors for crop production in Iran. This consistency, as well as widespread application in animal feeding, are the reasons for cultivating approximately 1.77 million hectares of barley, in which, 1.04 million hectares was attributed to rainfed barley. The previous studies demonstrated that there was a significant difference between the actual and potential yield of crops due to farm management condition. According to the calculated yield loss, the optimized crop field management is necessary to increase agricultural production. This study was aimed to estimate the yield and production gap of barley under rainfed condition as the first step in the terms of the schematization of stable increase in Iran.

This study is conducted based on the Global Yield Gap Atlas (GYGA) Protocol. As the first step in the implementation of present study, the main rainfed barley harvested areas were determined using GYGA climate zones and the distribution of rainfed barley harvested area maps and the country's meteorological station points layer. After defining the designated climate zones (DCZs) and the reference weather stations (RWSs), the collected data (2000-2014) of agronomic management, meteorological and soil characteristics in each region were employed to estimate the potential yield at the RWSs of rainfed barley as one of components of the yield gap calculation. Estimating barley potential yield under water-limited condition (Yw) was carried out by SSM-iCrop2 during 15 growing seasons. Moreover, the actual yield (Ya) data of rainfed barley was collected at the RWS level as another constituent for yield gap calculation. In the end, the estimated rainfed barley yield gap (Yg) in the RWSs was aggregated to DCZs and finally country-level.

In the current study, 38 RWSs within 17 DCZs of rainfed barley harvested areas were identified. The results showed that the average Yw was estimated 2723 kg. ha-1 and the range varied from 1072 to 4002 kg. ha-1. Ya range in the zones were calculated between 390 and 1510 with average of 1009 kg. ha-1. The results illustrated that there was a significant correlation between mean rainfall and maximum temperature during anthesis to harvest maturity period and Yw within 17 DCZs. Hence, with simultaneous increase in rainfall and decrease in average maximum temperature during this phenological period, concomitantly, the Yw value has been amplified. Yg values was estimated between 615 to 3125 kg. ha-1 (equivalent to 53 to 82% of yield gap (%)) with an average of 1714 kg ha-1. Improving the current management conditions to advance toward the attainable yield (Ya) (equivalent to 80% of Yw) in farmers' lands, can increase the average yield of rainfed barley from 1009 to 2178 kg ha-1. Based on the results, the country's production will grow from 1.05 million tons to 2.26 million tons in rainfed conditions through increasing yield to the level of attainable yield (80% of potential yield). The rate of barley import from other countries will decrease due to improvement in the production.

Our results showed 85 percent of rainfed barley production had been attributed to 17 designated climate zones. Due to the presence of 63% yield gap in rainfed barley fields, by considering 80% of this value as exploitable yield gap, the production can be increased to about 1.22 million tons which is appreciable for the economical and food security issues in Iran. It is not feasible to achieve the potential yield at the farmer level owing to existing constraints, but approaching the attainable yield by improving field management conditions can be accessible in the current situation.

Approximately 10% of the world's land is affected by flooding. Almost all crops, including wheat, are not tolerable to flooding stress. The occurrence of flooding stress in wheat has limited root growth, decreased dry matter accumulation, aging of the leaves before puberty, decreased tillering, production of insect florets, decreased hight, number of spikes and number of grain per spike, decreased biologicall yield, reduced 1000 grain weight and ultimately reduced grain yield. Accordingly, this study was carried out to evaluate the effects of flooding on grain yield and its components during tillering and stemming of wheat in two Morvarid and Koohdasht cultivars.

To conduct this research, a pot experiment was conducted in a completely randomized block design with factorial arrangement in Gorgan University of Agricultural Sciences and Natural Resources in 2016. The experimental treatments consisted of the duration of stress period at five levels (0, 7, 14, 21, 28 days) as the first factor, the time of flooding based on developmental stages (tillering and stemming) as the second factor, and the cultivars (Morvarid and Koohdasht) were considered as the third factor. In order to apply flood stress, the pots for each treatment were placed inside a pond filled by water, so that up to 2 cm from the stems were underwater. After applying stress treatments, traits such as leaf area, number of spikes per plant, number of seeds per spike, 1000 grain weight, biological yield, grain yield and harvest index were measured. Also, linear and nonlinear functions were used to describe the relationships between measured traits and flood duration.

The results of this study showed that the damages of flood stress in wheat depend on the time of plant placement under stress, the developmental stage where the stress coincides with it, and the type of cultivar used. In this study, characteristics such as leaf area, number of spikes per plant, number of grain per spike, 1000 grain weight, grain yield, biological yield and harvest index were significantly decreased by increasing the duration of flooding. The changes in some of the traits such as leaf area in Koohdasht cultivar, number of grain per spike in both cultivars, 1000 grain weight in Morvarid cultivar, and biological yield in both cultivars, followed by a segmented curve. So that in the first stages, Despite the increasing duration of flooding, each of these traits was fixed and unchanged, but, its value was linearly decreased by increasing duration of flooding to more than a certain limit for each trait. In other cases, the traits were reduced linearly from the beginning by increasing the duration of flooding. On the other hand, the number of grain per spike, grain yield, biological yield and harvest index in Kohdasht cultivar were always higher than Morvarid cultivars in different flooding treatments. Also, the highest flooding damage to leaf area, number of grain per spike, 1000 grain weight, grain yield and biological yield occurred when stress was applied at the stemming stage.

In general, flooding stress played a very important role in reducing wheat grain yield. In this regard, the length of stress period was the most important factor affecting the yield. The developmental stage and cultivar were ranked second and third in terms of importance, respectively. Therefore, due to the susceptibility of Golestan Province to flooding stress during tillering and stemming of wheat, it is very necessary to take the contraption to prevent of flooding in the fields and thereby prevent of yield losses.

Food security is a main subject in the world. Many international and governmental organizations to ensure the nutritional needs of human are being explored. According to the restrictions on agricultural lands, an increase in production per area unit is a way to improve food security. Despite high yielding varieties, these varieties do not reach their potential yield due to lack of access to favorable environmental conditions. Therefore, yield gap will be created between potential yield and actual yield. Before any progress in the agronomic operations of crop, it is necessary to identify the crop’s potential yield and to calculate the gap between potential and actual yield. Therefore, the aim of this study was to evaluate the historical trend in different yield gaps and to calculate different mean yield gaps in the studied region.

Potential and conventional yields were simulated using CropSyst model over 1981-2008 period and researchers’ potential yields over 1994-2008 period, maximum achievable yield over 1989-2008 period and actual yield over 1981-2008 period were collected from Agricultural Research Center, and Agriculture Organization. In this study, four types of yield gap were calculated as the difference between simulated potential yield and actual yield (yield gap 1), the difference between researchers’ potential yield and actual yield (yield gap 2), the difference between maximum achievable yield and actual yield (yield gap 3) and the difference between the simulated conventional yield and actual yield (yield gap 4).

The trend of changes in actual yield compared with both simulated potential and conventional yields over 1981-2008 period showed the gap between simulated potential and conventional yields with actual yield were decreasing. The decrease in the yield gaps was due to decrease in the trend of changes in simulated potential and conventional yields and increase in the trend of changes in actual yield over the studied period. According to the results, to increase the simulated potential yield, the varieties should be selected which have high radiation use efficiency. While for reducing the yield gap between simulated conventional yield and actual yield, the varieties with high radiation use efficiency should be cultivated under unlimited water and nitrogen condition. The trend of changes in yield gap between researchers’ potential yield and the actual yield was fixed yields over the period of 1994-2008 which was due to unchanged trend of both yields over this period. The trend of changes of the gap between actual yield and maximum achievable yield was increasing over 1989-2008. This was indicated the better management operations of prior farmers to achieve maximum yield, while other farmers did not work hardly to enhance the yield over the studied years. The simulated mean potential and conventional yield, the researchers’ potential yield, the maximum achievable yield and the actual yield were 6.35, 6.6, 6.0, 4.42 and 3.4 t ha-1, respectively, over 1994-2008 period. The differences between these yield levels with the actual yield were about 3.0, 1.0, 3.2 and 2.6 t ha-1.

It can be concluded that the difference between the management operations performed for achieving actual yield and the other yield levels can be created a yield gap and the more management differences, the higher yield gap.