Sajjad Rahimi-Moghaddam; Khosro Azizi; Hamed Eyni-Nargeseh; Seyed Ahmad Kalantar Ahmadi
Abstract
Introduction: Canola is one of the most important oilseed crops in overall the world. This oilseed crop is mainly utilized for its high oil content (with about 40–45% oil). However, in recent years, the area under cultivation of canola has got decreased due to water scarcity. Applying drought tolerant ...
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Introduction: Canola is one of the most important oilseed crops in overall the world. This oilseed crop is mainly utilized for its high oil content (with about 40–45% oil). However, in recent years, the area under cultivation of canola has got decreased due to water scarcity. Applying drought tolerant cultivars (Shirani Rad et al., 2013) with high water use efficiency can help to develop the area under cultivation of canola and increase canola production. Therefore, the current study was conducted to assess the water use efficiency of spring canola cultivars in warm and temperate climates.Material and methods: This study investigated the different cultivars as a strategy for increasing canola production and improving its water use efficiency under different climate types in Khuzestan and Lorestan provinces. For this purpose, four locations including Khoramabad and Kuhdasht in Lorestan province as temperate semi-arid climate regions and Dezful, and Shushtar in Khuzestan province as hot and arid climate regions were selected. Daily long-term climatic data (included minimum and maximum temperatures, rainfall, and global radiation) were collected for these locations from Iran Meteorological Organization. In this study, Hyola308 (early-maturity), Hyola401 (mid-maturity), and RGS003 (late-maturity) cultivars were used. In order to simulate the growth and yield of canola in different locations APSIM-Canola model (Robertson and Lilley, 2016) was employed. OriginPro 9.1 software (Seifert, 2014) was considered for all statistical analyses and drawing of figures.Results and discussion: The results showed that grain yield, biomass, water use efficiency, grain weight, actual evapotranspiration, the average temperature during canola growth period, and the length of the canola growth period were substantially affected by cultivar and region (climate type). According to results, the highest grain yield and water use efficiency (3037 kg ha-1 and 6.9 kg mm-1 ha-1, respectively) were achieved for mid-maturity cultivar (Hyola401). Furthermore, simulation results revealed that temperate and semi-arid regions compared to hot and arid regions increased grain yield, biomass and water use efficiency by 2507 kg ha-1, 10100 kg ha-1, and 2.7 kg mm-1 ha-1, respectively. Khorramabad × Hyola401 treatment had the highest water use efficiency, grain yield, and biomass (9 kg mm-1 ha-1, 4954, and 17943 kg ha-1, respectively) due to lower the average temperature during canola growth period (10.9 ° C) and higher the length of the canola growth period (2424.9 day) while the lowest amount of these traits was recorded in Dezful × Hyola308 treatment (5 kg mm-1 ha-1, 1369, and 5514 kg ha-1, respectively).Conclusion: The results indicated that expanding of canola cultivation in temperate regions can be used to boost the canola production in Iran and to improve the sustainability of canola cultivation agroecosystems. Also, using a mid-maturity cultivar such as Hyola401 in both temperate and hot climate conditions can increase water use efficiency and sustainability of canola production agroecosystems through higher production per water consumption.
Khosro Azizi; Sajjad Rahimi-Moghaddam
Abstract
Introduction: Heat stress is one of the most important threats and concerns for maize production, which mostly occurs in hot and dry areas. Heat stress reduces grain yield and the plant's photosynthesis rate and increases transpiration. Maize is very sensitive to heat stress and extreme temperatures ...
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Introduction: Heat stress is one of the most important threats and concerns for maize production, which mostly occurs in hot and dry areas. Heat stress reduces grain yield and the plant's photosynthesis rate and increases transpiration. Maize is very sensitive to heat stress and extreme temperatures at the flowering stage because extreme temperatures decrease pollen germination ability, and thus, decrease grain yield. However, there are some strategies to prevent the maize flowering stage from being exposed to heat stress. Careful management practices including adjusting the sowing time and cultivar can be considered as useful strategies to deal with heat stress. Crop simulation models can be used to investigate these practices. Therefore, the present study was carried out to evaluate the risk of heat stress (frequency and intensity of heat) on grain maize of Iran and evaluate the risk window for grain maize using the modeling approach. Material and methods: In order to evaluate the risk of heat stress in maize agroecosystems of Iran, a simulation experiment was designed in five regions (Iranshahr, Dezful, Parsabad, Kermanshah, and Kerman), three sowing times (common: farmers sowing time in each region; late: 20 days after common sowing time; early: 20 days before common sowing time), and two cultivars (SC704 and SC260 as late- and early-maturity cultivars, respectively). To do this, the long-term climatic data of each region including minimum and maximum temperatures, rainfall, and radiation were collected from Iran Meteorological Organization. These data were applied as inputs of the crop simulation model. In this study, the APSIM model was employed to simulate the growth and development of the maize plant. In order to assess the risk of heat stress on grain maize, three dimensions including the critical stage of grain maize to extreme temperatures (flowering), frequency of extreme temperatures at the critical stage, and intensity of extreme temperatures at the critical stage were evaluated. Furthermore, the risk window for maize flowering in each region was equal to the first day of the year with a temperature of over 36 °C until the last day of the year with a temperature above 36 °C. Results and discussion: The highest risk window of extreme temperatures was recorded in Iranshahr County (183 days) as a hot and dry region and the lowest risk window was simulated in Parsabad (14 days) as a semi-arid and temperate region. Moreover, the percentage of the number of maize flowering days with temperatures above 36 °C and the mean maximum temperature during the flowering period were 63.5% and 37.09 °C, respectively. This issue reduced the grain yield of maize in Iran so that the grain yield was simulated 6196.5 kg ha-1 . However, in the spring season, the early sowing time and the early-maturity cultivar decreased the percentage of the number of maize flowering days with temperatures above 36 °C (37.2%) and mean maximum temperature during the flowering period (35.1 °C) and increased grain yield (7486.9 kg ha-1 ). Overall, in the summer, the percentage of the number of maize flowering days with temperatures above 36 °C and mean maximum temperature during the flowering period were decreased 38.9% and 35.3 °C, respectively, and grain yield was boosted to 7743.6 kg ha-1 under the combination of late sowing time and late-maturity cultivar. Conclusion: The results showed that grain maize is currently cultivated by farmers under high-risk conditions of heat stress. In order to reduce the risk and increase grain yield, farmers in each region should apply the optimal sowing times and cultivars according to the growing season.
