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After soybean and oil palm, rapeseed has the third place in supplying vegetable oil in the world, so that it accounts for 14.7% of the total production of vegetable oil. The current research was carried out using modeling approach in order to simulate the replacement of wheat cultivation with rapeseed cultivation in terms of water and economic productivity in four locations (Aleshtar, Khorramabad, Pol-e Dokhtar, and Kuhdasht) in Lorestan province. APSIM model was used to simulate the growth and yield of wheat and rapeseed crops. The model validation results showed that it accurately simulates wheat and rapeseed grain yield with nRMSE of 8.6%. The results showed that wheat cultivation (3524.4 kg) had a higher grain yield than rapeseed cultivation (2750.2 kg). In addition, wheat cultivation system (1.45 kg m-3) compared with rapeseed cultivation (1.15 kg m-3) had higher water productivity. However, the difference between these two cultivation systems in terms of irrigation productivity was not considerable (0.11 kg m³). Also, economic productivity and net income of rapeseed cultivation system were 0.220 million tomans per cubic meter and 59.9 million tomans per hectare, respectively, while they were 0.014 million tomans per cubic meter and 41.1 million tomans per hectare, respectively, for wheat cultivation system. In general, the results approved that moving from wheat cultivation to rapeseed cultivation can be environmentally and economically sustainable in the agro-ecosystems of Lorestan province, especially in Khorramabad county. [ABSTRACT FROM AUTHOR]

A two-year experiment was arranged as a factorial in a randomized complete block design with three replicates to investigate the response of camelina oil yield and its oil composition to irrigation regimes at different sowing dates in Karaj, Iran. The experiment factors were irrigation regimes including (i) full irrigation (well-watered), (ii) restricted irrigation from silicle formation (late-stress), (iii) restricted irrigation from flowering (mild-stress) and (IV) restricted irrigation from maximum stem length (early-stress) and planting dates consisting of (i) 27-Sep, (ii) 12-Oct and (iii) 25-Oct. The highest oil content (30.04%) was obtained from the first sowing date and was 2% and 5.4% higher than 12-Oct and 25-Oct, respectively. Obtained grains from well-watered irrigation regime had significantly more oil content (31.02%) than the other irrigation regimes. Delaying in sowing date and water-deficit stress raised saturated fatty acids (palmitic, stearic and arachidic acids). While delayed sowing date (12 and 25-Oct) and water-deficit stress (low, mild and severe stresses) increased the content of palmitic, eicosenoic and erucic fatty acids, the oleic, linoleic and linolenic acids were reduced in such conditions. It seems that postponing the sowing date to 12-Oct and restricting irrigation from silicle formation would be reasonable as it can decline water consumption. [ABSTRACT FROM AUTHOR]

Introduction Improving crop yields can meet the projected demand in developed and developing countries as a key and promising solution. To increase dryland wheat production in arid and semi-arid regions such as Iran, researchers and crop breeders need to understand the drought pattern (in terms of time and intensity) occurring in wheat agro-systems because depending on the time and intensity of drought stress, drought stress impacts on different processes and genes of crops. To accurately study the drought pattern of dryland wheat and different cultivars adapted to these conditions, researchers need to design multienvironmental field experiments, which are time-consuming and costly. Under these circumstances, some essential information is limited in the field experiments, especially when done for only a few years, and basically does not indicate fluctuations in the target environments. In contrast, the modeling and simulation approach is a useful method for comprehensive environmental impact assessment. Materials and Methods This study was conducted to identify and study different drought patterns in 8 locations including Ardebil, Khalkhal, Maragheh, Marand, Meshginshahr, Sarab, Tabriz, and Urmia in the northwest of Iran. APSIM model was used to simulate the growth and development of dryland wheat in the study locations. The long-term climatic included minimum and maximum temperatures, rainfall, and radiation (1980 to 2016) collected from the Meteorological Organization of Iran. These data were used as input to the crop growth simulation model. Water supply and demand index was used to determine different drought patterns. This index is obtained by dividing soil water content to plant water demand (WSDR). After calculating the water supply and demand index for each year and region, the CLARA clustering method was used to classify and group the index. The number of groups obtained by CLARA method was equal to the type of drought patterns of dryland wheat. Results and Discussion The results showed 4 different drought patterns during the dryland wheat growing season in the study locations. Drought pattern 1 showed no drought stress or mild drought stress throughout the growing season of dryland wheat. Under drought pattern 2, drought stress started before flowering and ended during seed filling. For drought pattern 3, water stress started from the time of germination but removed during the vegetative growth period. Drought pattern 4 started in the early stages of growth and continued until the end of the dryland wheat growing season. The frequency of occurrence of 1, 2, 3, and 4 drought patterns was 27.8%, 26%, 8% and 38.2%, respectively. On average across locations, transpiration was 160, 137.1, 31, and 86.7 mm for 1, 2, 3, and 4 drought patterns during the wheat growing season. Also, a significant difference was observed among different drought patterns in terms of biomass that biomass under drought patterns 1, 2, 3, and 4 was equal to 13411, 10076, 2097 and, 6435 kg ha-1, respectively. Grain yield under drought pattern types 1, 2, 3 and 4 were 3738.7, 2949.7, 694.6, and 1456.2 kg ha-1, respectively. The highest percentage of light and mild drought patterns (1 and 2) was related to Marand region with 100% and Sarab region experienced more severe drought patterns (3 and 4) than other regions (88.2%). Under different locations and drought patterns, on average across years, the highest grain yield was simulated for Marand under drought pattern 1 (4759 kg ha-1) and the lowest was recorded for Urmia under drought pattern 3 (208.8 kg ha-1). Conclusion In general, the simulation results showed that 4 different types of drought patterns were observed during the dryland wheat growing period in the study locations. The frequency of occurrence of 4 drought patterns was various in the study locations and the grain yield varied under the drought patterns. However, the highest occurrence was related to drought pattern 4, under which drought stress begun in the early stages of growth and lasted until the end of the dryland wheat growing season. Accordingly, it is suggested to consider various strategies such as using cultivars with short maturity period to avoid drought stress at the end of the season and using cultivars with high resistance to drought stress (especially in the flowering period). [ABSTRACT FROM AUTHOR]

This study assessed the growth of wheat under climate change conditions (increases in CO2 and temperature) in southwestern Iran. Future climate data were projected using long‐term climate data for radiation and minimum and maximum temperatures for the baseline period 1980–2010. The future climate scenarios made use of delta changes from the Coupled Model Intercomparison Project Phase 5 (CMIP5) in the R package of the Agricultural Model Intercomparison and Improvement Project for 2040–2070. After generating the weather data, the Agricultural Production System Simulator wheat model was applied to assess the potential impact of climate change on wheat yield and the relative growth rate, crop growth rate, total dry weight and leaf area index. Averaged across all locations, an increase of 1.6 and 2.3°C in annual temperature was projected under representative concentration pathway 4.5 (RCP4.5) and RCP8.5, respectively. The decrease in the average length of the growing season was 7.5 and 9.3% under RCP4.5 and RCP8.5, respectively, in the mid‐21st century with respect to baseline. The mean cumulative radiation will decrease by 11.6 and 14.3% averaged across all sites for RCP4.5 and RCP8.5, respectively. Grain yield will decrease at all sites for both RCPs. The greatest decrease in wheat yield was projected for Izeh under RCP4.5 and RCP8.5 (7.9 and 9.3%, respectively) for 2040–2070 relative to baseline. A greater grain yield at baseline than for the RCP8.5 and RCP4.5 scenarios was closely related to higher leaf area index, relative growth rate and crop growth rate values during the reproductive phase. Thus, these parameters can be defined as indicators of crop yield. [ABSTRACT FROM AUTHOR]

To select and introduce the best rapeseed genotypes under withholding irrigation, two field experiments were carried out in seasons 2015–2016 and 2016–2017 in Iran. Factorial arrangement of treatments was set up as RCBD with three replications. The experiment factors were two irrigation treatments (normal irrigation during the growing season and withholding irrigation from silique setting stage until the end of the growing season) and 17 genotypes of rapeseed. Grain yield, oil content and fatty acid contents were measured. The results revealed that oleic acid (62.15%) was the highest followed by linoleic (19.28%), linolenic (5.65%), palmitic (5.24%) and stearic acids (2.44%). ODR (oleic desaturation ratio) and LDR (linoleic desaturation ratio) were significantly affected by genotypes and irrigation treatments. The biosynthetic pathway of fatty acids affected by drought stress. This means that linoleic acid increases under withholding irrigation condition, while linolenic acid decreases in such a water deficit stress condition. The highest performance of qualitative and quantitative was detected in HL3721 genotype due to high values of grain yield (3892.45 kg ha−1), oil content (437.05 g kg−1), unsaturated fatty acids (87.63%) and low values of saturated fatty acids (7.98%), and it could be used under withholding irrigation in arid and semi-arid climates. [ABSTRACT FROM AUTHOR]

• This research analyzed three rice production systems and recommended ways to improve their sustainability and efficiency. • All three systems were inefficient and unsustainable since they relied on purchased resources. • The dry bed seeding method is recommended since it can save 30–60% of irrigation water. This research was conducted with the aim of (i) evaluating the sustainability of three rice production systems (DBS: dry bed seeding, TP: transplanting, and WBS: wet bed seeding) in Khuzestan province, Iran, (ii) introducing the most cost-effective and sustainable system, and (iii) providing solutions to increase the systems' sustainability and efficiency. In order to analyze the studied systems during the 2020–2021 growing season, several emergy-based and economic indicators were analyzed. The total emergy inputs supporting the systems are estimated to be 2.69E+16, 4.16E+16, and 3.17E+16 sej ha−1 yr−1 for DBS, TP, and WBS, respectively. The three studied farming systems were determined to be inefficient and unsustainable due to their reliance on purchased resources including labor, fossil fuel, and seed/transplant. According to the environmental loading ratio and modified environmental loading ratio indicators, the WBS and TP systems exerted less pressure on ecosystems and were more sustainable than the DBS system due to the greater quantity of purchased renewable flows (labor and seed/transplant). The results of the emergy renewability, emergy sustainability index, and modified emergy sustainability index indices indicated that the three investigated systems were not sustainable, indicating that high energy consumption in rice farming systems resulted in a significant environmental burden. The economic analysis of rice production systems revealed that the DBS system was economically superior due to its lower total production costs, especially labor costs, when compared with the other two systems. In light of the water scarcity crisis in Iran, the DBS method is recommended due mainly because of its ability to save 30–60% of irrigation water in the studied areas compared with the other two systems that have high water consumption. Due to the lower sustainability and greater environmental pressure of the DBS method compared with the two studied farming systems, it is also recommended to decrease the proportion of nonrenewable inputs (fossil fuel, chemical fertilizers, and herbicides) and increase the proportion of renewable inputs (organic fertilizer). [Display omitted] [ABSTRACT FROM AUTHOR]