جستجوی مقالات مرتبط با کلیدواژه « درجه روز-رشد » در نشریات گروه « زراعت »

This study aimed to investigate the effect of sowing date and enviromental factors during different growth stages on some phenological characterisitcs and grain yield of commercial bread wheat cultivars. The experiment was carried out as split-plot arrangements in randomized complete block design with three replications at the Darab reaesrch field station in 2018-19 and 2019-20 cropping cycles. Five sowing dates: October 27, 11, and November 26, December 11, and 26, were assigned to the main plots. Five commercial wheat cultivars: Mehregan, Barat, Khalil, Sarang, and Setareh, were randomized in the subplots. Results showed that the late maturity cultivars, Khalil and Brat, had higher grain yield in earlier sowing dates. Early maturity cultivars, Setareh and Mehregan, had less yield reduction in later sowing dates. The highest and lowest mean grain yield obtained from November 11 (6934 Kg ha-1) and December 26 (5775 kg ha-1), respectively. Number of days and required growing degree-days (GDD) decreased with delaying sowing date. The decrease of required GDD to reach commencement of stem elongation, anthesis and maturity stages from the first to fifth sowing date was 181, 282 and 528 GDD, respectively. Simultaneous effect of weather variables and sowing date on some characteristics revealed that the first two components explained approximately 41% of total variation. Results showed that temperature was the most important factor controlling the phenological stages duration. Despite the importance of temperature, changes in sowing date can alter the required GDD for phenological stages due to other environmental factors. In general, the results of this study can provide an insight into bread wheat cultivars responses to different climatic conditions and development of new bread wheat cultivars adapted to target environments.

With the increase in population and improvement in diet diversity, there is a growing need for the quantitative and qualitative development of oil seeds. Camelina (Camelina sativa), an oil seed plant from the Brassicaceae family, is an ideal candidate as it contains 50 to 60% unsaturated fatty acids and omega-3 fatty acids, and has the ability to thrive in adverse environmental conditions. By introducing this new oil plant into cultivation programs, it can significantly contribute to the production of high-quality edible or non-edible oil in the developing countries such as Iran. However, achieving maximum grain yield and appropriate fatty acid composition in camelina oil relies heavily on selecting the appropriate planting date. Additionally, providing necessary nutrients, particularly nitrogen, to the plants is a key aspect of agricultural management to achieve desired quality and quantity of crop products. This research aims to investigate the impact of planting date and different levels of chemical and biological nitrogen fertilizers on the growth characteristics, yield, and oil content of camelina plants in the Eghlid, south of Iran.

This research was conducted in the cropping year of 2021-2022 at the Eghlid Agricultural Research Station in Fars province, south of Iran (Long. 52 42, Lat. 30 55, and Alt. 2375 m above sea level). The experiment was performed as a split-plot design based on a randomized complete block design with three replications. The main plots included different nitrogen fertilizers at four levels: 100% chemical nitrogen (250 kg/ha urea), 75% chemical nitrogen (187 kg/ha urea) + nitrogen biofertilizer, 50% chemical nitrogen (125 kg/ha urea) + nitrogen biofertilizer, and non-use of nitrogen fertilizer (control). The sub-plots included four planting dates: September 11, 2021, September 26, 2021, April 9, 2022, and April 24, 2022. The experimental plots (sub-plots) were determined to be 5 x 2 meters. Each plot consisted of 4 stacks with a distance of 50 cm between them. The distance between sub-plots was 50 cm, the distance between main plots was 150 cm, and the distance between replications (blocks) was 300 cm. On both sides of each stack, seeds were planted in two rows with a distance of 25 cm to achieve a density of 120 plants/m2. One-thirds of the urea nitrogen fertilizer was added to the plots of each treatment before planting, one-thirds at the 6-8 leaf stage, and the remaining third at the stemming stage of camelina. In the biofertilizer treatment, the camelina seeds were inoculated with biofertilizer containing Azotobacter sp. and Azospirillum sp. before being sown. The cumulative growth degree days of seedling emergence, flowering, and ripening, as well as plant height, chlorophyll index, grain yield, yield components and seed oil percentage were evaluated.

With delaying planting from September 11, 2021, to April 24, 2022, the GDD (Growing Degree Days) for camelina emergence decreased, additionally, a delay in planting led to a shorter growth period until full flowering of the camelina plants. Planting in September 26, 2021, led to the longest growth period until full maturity of the camelina plants, while spring planting resulted in a decreased length of the growth period until maturity. The highest plant height (43 cm) was achieved in the presence of 75% chemical fertilizer + biofertilizer nitrogen and the lowest (41 cm) was in the absence of nitrogen fertilizer application. The planting date of September 11, 2021 and April 24, 2022 showed the highest (43 cm) and lowest (37 cm) plant height of camelina. The decrease in plant height during the late planting date was primarily due to the decrease in internode elongation as a result of changes in day length and a shorter vegetative growth period. The highest chlorophyll index (66) was achieved by using 100% nitrogen chemical fertilizer, while the lowest chlorophyll index (52) was observed in the control, lack of fertilizer application. This trait decreased when the planting was delayed. The delay in planting led to a decrease in leaf area, resulting in a decrease in the chlorophyll index during the late planting date. No application of nitrogen fertilizer had the highest seed oil percentage (29.4%), while the application of 75% chemical fertilizer + biofertilizer nitrogen resulted in the lowest oil percentage (18.5%). The delay in planting from early autumn to late spring led to a decrease in the seed oil percentage. This decrease can be attributed to increase in nitrogen content, which promotes the formation of nitrogenous protein precursors. Consequently, more photoassimilates are allocated to protein formation, reducing the available photoassimilates for fatty acid synthesis and, ultimately, limiting oil production capacity. The decrease in oil percentage observed in the most delayed planting dates is likely due to the increase in temperature during the seed filling stage and the reduction in net photosynthesis.
Mean comparison of the interaction between nitrogen fertilizer and planting date on camelina grain yield showed that applying 75% chemical fertilizer + biofertilizer nitrogen, compared to no nitrogen fertilizer, on planting dates of September 11, 2021, September 26, 2021, April 9, 2022, and April 24, 2022, increased grain yield of camelina by 80, 100, 150, and 190 percent, respectively.

The Findings show that in the Eghlid region, autumn-sown camellia out-yields spring-sown one. Additionally, by using a combination of 75% chemical fertilizer and nitrogen biofertilizer, a higher grain yield is achieved compared to using 100% nitrogen chemical fertilizer alone. Considering the importance of production of oilseed plants, like camellia, in Iran and the need for sustainable plant production programs, it appears that growth-promoting bacteria can play a significant role in reducing the need for nitrogen fertilizers.

This study aimed to investigate the response of four ecotypes of milk thistle from Isfahan, Kohgiluyeh va Boyer Ahmad, Khuzestan-Omidiyeh, and Hungary to three irrigation regimes (irrigation after 40%, 60%, and 80% maximum allowable depletion of available soil water (evaluated in 2020-2021 under five different planting dates (September 27th, October 17th, November 6th, November 26th, and March 10th) at the research farm of Isfahan University of Technology in Iran. The experiment was conducted as a combined analysis of a split-plot based on randomized complete block design with three replications. The results showed that the highest and the lowest grain yield and shoot dry weight of milk thistle plants were obtained under the October 17th and March 10th planting dates, respectively. Water deficit at both levels decreased grain yield, shoot dry weight, number of flowers per plant, plant height, flowering degree-days, and physiological maturity degree-days, but increased grain and shoot water use efficiencies. The "Kohgiluyeh and Boyer Ahmad" ecotype exhibited the highest seed yield, shoot dry weight, seed/shoot water use efficiency, and harvest index, making it a promising candidate for breeding programs aimed at creating adaptive cultivars of the milk thistle plant. Based on the study's findings, it can be concluded that milk thistle should be planted in the fall season from late September to mid-November under similar climate conditions.

This research was conducted to compare agro-meteorological indices and yield of short day onion cultivars. The experiment was done in randomized complete block design including 15 cultivars (Seba, Imperateriz, Siroos, 7030, S.V. 4043, X. P. Red, Sweet Ajent, Savana Sweet, Golden I, Primavera, Texas Early White, Texas Early Grano, White Grano, Spidan and Contessa) with four replications at Behbahan Agriculture Research Station, southwest of Iran, for two years (2016-18). Seeds were sown in nursery in early October and seedlings were transplanted in early November. Bulbs were harvested when 50-80% of foliage had senesced and fallen. The differences of growing degree days and helio thermal unit were considerable among cultivars from planting to bulbing stage, however the differences of photo thermal index were not significant among cultivars at this stage. During bulbing and bulb development stage differences of growing degree days, helio thermal unit and photo thermal index were considerable among cultivars. Evaluation the correlation coefficients among yield and agro-meteorological indices during bulbing and bulb development stage suggested significant negative correlation of bulb yield with growing degree days and photo thermal indices. The highest bulb yield, thermal use efficiency and helio thermal unit use efficiency were recorded in Siroos (hybrid cultivar). As the seed price of open–pollinated cultivar is less than the prices of hybrid cultivars and the seed of open-pollinated cultivars could be produced by the growers, therefore, planting of Texas Early Grano (open-pollinated cultivar) is recommended for onion production in Khuzestan province at southwest of Iran.

Among various non-biological stresses, drought stress is the most important factor that has limited production in the agricultural sector of the country (Akhzari and Pessarakli, 2016). Today, the supply of oilseeds for the extraction of vegetable oils needed for various industrial, edible, medicinal and cosmetic uses is one of the basic needs of the current population growth (Beynam, 2015). Balangu (Lallemantia iberica L.) is an annual, herbaceous and drought-resistant plant belonging to the mint family (Lamiaceae). With medicinal-oil properties, it is considered a multi-purpose plant in agriculture (Hendawy et al., 2015). In order to check and predict the phenological stages of the planted plants in an area, the relationship between the phenological stages and the thermal factor should be considered. For this purpose, thermal units of growth degree days (GDD) are used to check the amount of heat needed to pass each growth stage of plants (Kumari et al., 2020). In plants under drought stress, where the absorption of nutrients through the root faces a problem due to the decrease in soil water volume, the absorption of micronutrients such as iron and zinc can be effective through foliar spraying. (Rafique et al., 2015). In the conditions of lack of water resources, like what is happening in our country, it is necessary to change the agricultural pattern towards planting plants adapted to dry land, as well as ways to increase yield per unit area. Therefore, the purpose of this research was to investigate the development of Balangu planting and the role of foliar application of iron and zinc micronutrients on phenology and the adjustment of stress effects.

This research was conducted in the research farm of Razi University of Agriculture and Natural Resources, Kermanshah during two consecutive years (2017-2018 and 2018-2019) as a split-plot-factorial experiment in the form of a basic randomized complete block design with three replications. The experimental treatments include: irrigation (Water deficit after flowering and Normal) in the main plots, foliar spray factors (zero, four and eight per thousand concentrations of iron and zinc sulfate) and foliar application time (at the beginning of the vegetative and reproductive growth stage) were factorially placed in sub-plots. The seeds (native population of Songhor region of Kermanshah province) were planted manually at a depth of two centimeters and with a density of 400 plants per square meter in a row at the first appropriate time in late March of 2017 and 2018. Application of nitrogen, phosphorus and potash fertilizers was based on need. Dehydration stress was applied by stopping irrigation from the time of full flowering (opening of 50% of flowers).

The results showed that, with the application of water stress, the seed yield and oil yield decreased by 24% and 17%, respectively, and the oil percentage increased by 8% compared to the treatment without water stress. Also, water deficit stress reduced the number of days and heat requirement to maturity by 10 days and 275 growth days degree, respectively. The greatest increase in oil yield compared to the treatment without foliar spraying (control) was related to the 4 and 8 per thousand zinc foliar treatments in reproductive stage and under stress conditions, which increased these traits from 339 and 283 respectively in conditions Lack of stress and water deficit stress increased to 539 and 513 kg/ha. The greatest effect of iron and zinc foliar application treatments on increasing plant height and the number of days and heat requirement to maturity stage was related to 4 and 8 per thousand iron and zinc foliar application in the vegetative growth stage.

In the present study, it can be concluded that the Balangu having adaptability, suitable production, relatively short growth period and matching the length of the growth period with the rainfall of the study area, and it can be considered as a common plant for rotation in this region. Foliar application of iron and zinc micronutrient elements should be used by farmers to moderate the effects of water deficit stress, taking into account its small and economical amounts.

This research was carried in cropping years 2017-18 and 2018-19 to study the effect of plant density on morphological traits, flowering pattern, boll production and seed cotton yield of new cotton cultivars in Varamin region of Iran. In this research, five cotton cultivars including Varamin, Shirpan603, Cocker100, NO200 and SP731 in three plant densities were evaluated using a factorial experiment in a randomized complete block design with three replications. In this study, the number of flowers and flowering date in cultivars for 11 weeks (1 July to 15 September) were counted. The results of analysis of variance showed that the differences between cultivars were significant for plant height, number of nodes, number of flowers, number of bolls and fiber and seed cotton yield at 1% level. The results also showed that there is a significant difference between the years of project implementation for plant height, number of bolls and fiber and seed cotton yield at the level of 1%. The mean of plant height for the first and second years were 93.2 and 119.9 cm and the average number of bolls per plant were 15.9 and 11.41 and the seed cotton yield were 5242 and 4050 kg/ha, respectively. In this study cultivars did not differ significantly in terms of number of days from planting to flowering, number of days from flowering to harvest and early ripening. Investigation of flowering process in 11 weeks showed that the peak of flowering for both years of research was the eleventh week after planting with an average of 41.8 and 44.6 flowers per plant. Most of the bolls were produced from the flowers of the eleventh week for first year and from the flowers of the tenth week for second year. The cumulative growing degree days during the vegetative and reproductive growth period for two years of experiment was significantly different.  So that at the end of the seventeenth week after planting (last week of flowering) the cumulative growing degree days in the first and second years was 1734.9 and 1245.5, respectively, Which can be one of the important reasons in reducing the number of bolls and fiber and seed cotton yield in the second year.

Climate change is rapidly degrading the conditions of crop production. For instance, increasing salinization and aridity is forecasted to increase in most parts of the world. As a consequence, new stress-tolerant species and genotypes must be identified and used for future agriculture. Stress-tolerant species exist but are actually underutilized and neglected. Quinoa, scientifically known as Chenopodium quinoa Willd. is a member of the Amaranthaceae family. Promoting the cultivation and nutrition of quinoa will diversify food products in the country, sustainable production, increase farmers' incomes and provide part of the community's food needs. Crop simulation models have been used for various studies such as selecting the appropriate cultivar, determining the best planting date, predicting the effect of diversity and climate change on growth. Field research requires a lot of time and money, while computer simulation models can save time and money by conducting extensive experimental simulations.

This research was conducted in two regions of Yazd province with 10 separate experiments in the form of a randomized complete block design with 3 replications. Experimental factors included 5 promising modified lines in Yazd Salinity Research Center with Titicaca cultivar. The lines consisted of four intermediate maturity lines, numbered 1 (NSRCQE), 2 (NSRCQC), 3 (NSRCQD), and 6 (NSRCQA), one late maturity line numbered 4 (NSRCQB), and the early maturity cultivar Titicaca numbered 5. Sampling and note-taking were performed regularly, once every three days, in proportion to the progress of the phenological stages of each line. A model based on degree-day-growth was prepared in FST language. In preparing the length table, due to the short day of Quinoa, for all lines in the model up to 12.5 hours, the development rate was one, and after 13.8 hours, the development rate was zero. The base temperature in the model was 2 °C. Then, the model was calibrated and evaluated with data taken from the field.

RMSE (CV) coefficient of variation between 7 to 12%, root mean square error (RMSE) between 4.4 to 6.4 days, Wilmot agreement index (d) between 0.99 to 1, model efficiency (ME) between 0.96  to 0.98, the mean deviation from the model (MB) was between 0.05 to 0.08 and the coefficient of determination (R2) was between 92 % to 98%. These values indicated a good estimate of the day to flowering of quinoa with the model written in FST language, and the values of day to flowering simulated gained the necessary validity. The coefficient of variation of nRMSE (CV) is between 6.8 to 8.6%, the root mean square error (RMSE) is between 6.2 and 8.7 days, the Wilmot agreement index (d) is between 0.75 and 0.92, The mean deviation from the model (MB) was between 0.05 to 0.08 and the coefficient of determination (R2) was between 92% and 98%. These values indicated a good estimate of the day to physiological maturity with the model written in the FST language, and the day values to the simulated physiological maturity gained the necessary validity. Calibration and evaluation of model efficiency using root mean square error (RMSE), coefficient of variation or nRMSE percentage (CV), Wilmot agreement index (d), model efficiency (ME), and mean model deviation (MB), coefficient of explanation (R2), line test 1: 1 day until germination, flowering and good physiological maturity was estimated.

The results of this study indicated that, the quinoa model prepared for quinoa in terms of degree-day-growth well predicts the developmental stages (emergence, flowering and maturation) of this plant in terms of maturity (early, medium and late) and can be its help determined the appropriate planting date in different areas. This calibrated sub-model can now be used to evaluate different temperature and photoperiod effects for decision making in a wide range of growth environments in quinoa cultivation systems in current and future climatic conditions. Therefore, this sub-model can be used in educational-research and applied work in the field.

Wheat (Triticum aestivum L.) is one of the most important crops in the world as well as in Iran. It has experienced many improvements in terms of yield and quality traits during recent decades. Wheat, like energy, is known as a strategic commodity and is one of the important indicators of agriculture. This plant has the highest area under cultivation and production among other cereals in the world. Planting date is an important factor in crop production because meteorological parameters vary with changes in planting date. Delay in planting is one of the problems that is common in almost all wheat growing areas of Iran and is one of the main causes of reduced yields of wheat cultivars. Yield reduction rate varies depending on the delay in planting and cultivars, and the results of some experiments indicate that this amount sometimes reaches more than 35% of potential grain yield. Phenology and growth rate due to their effect on duration and the occurrence of different stages of development and the environmental conditions prevailing in each of these stages, are the key point of adaptation to various environmental conditions such as delayed planting date. This experiment was designed to identify the changes in yield and yield components and phenological stages of new bread wheat cultivars with different growth habits and to investigate the possibility of introducing cultivars compatible with delayed planting date in the region.

This research was conducted in two separate experiments based on a complete randomized block design with optimum planting date (6th November) and delayed planting date (6th December) on 10 new bread wheat cultivars with three replications on the research farm of the Seed and Plant Improvement Research Institute in Karaj in two years (2016-2018). The bread wheat cultivars include Pishgam, Heidari, Rakhshan, Sivand, Baharan, Sirvan, Parsi, Mehregan, Chamran 2 and Chamran. Yield and yield components such as number spike per m2, number of grain per spike, 1000-grain weight were measured at the end of the growing season to evaluate responses of the cultivars to the various planting dates. In addition, the phenological stage was recorded during the growing season.

Results indicated that delayed planting date from 15th Nov. to 15th Dec. caused a significant reduction on grain yield (from 7485 to 6066 kg.ha-1), number of spikes per m2 (from 698 to 605), number of grain per spike (from 28.5 to 25.8 seed), and 1000 grain weight (from 41.1 to 38.4 g). The interaction effects of planting date and cultivars were significant on grain yield and yield components. The highest and lowest grain yield belonged to Pishgam (7436 kg. ha-1) on optimum planting date and Chamran (5842 kg.ha-1) on delayed planting date, respectively. Delayed planting date reduced duration of planting to double ridge (from 736 to 641 GDD), planting to terminal spikelet (from 982 to 886 GDD), planting to anthesis (from 1608 to 1457 GDD) and planting to maturity (from 2456 to 2265 GDD).

Duration of different developmental stage is very important for the formation of yield components that determine the final grain yield. Although these stages are a genetic trait, but they are affected by plant growth conditions and environmental stresses, climatic factors, especially temperature and day length. Our research showed that delay in planting reduced grain yield by 18% compared to the optimum planting date because of the reduced number of spikes per m2 and vegetative and grain-filling periods.Based on the results, in cases of delayed planting date (unfavorable weather conditions, insufficient planting equipment, etc.) in Karaj region or similar climatic regions, early maturity cultivars such as Mehregan and Chamran 2 and moderate maturity cultivar like Sivand are recommended in order to minimize yield loss.

In order to evaluate the effects of planting date and plant density on phenology, seed yield, and essential oil quality of Guar, an experiment has been conducted during 2018-2019 and 2019-2020 growing seasons. It is a split plot layout based on a randomized complete block design with three replications. Different planting dates are considered as the main factor, including September 5th to February 5th as monthly. Three plant densities are considered as sub-factor (20, 40, and 60 plants in a square meter). The required growing degree- day (GDD) from sowing to physiological maturity ranges between 1802.3 and 2347.9 °d on different planting dates. The highest GDD from sowing to physiological maturity is observed on May 5th. The highest seed yield (3780 kg / ha) and galactomannan yield (1050 kg / ha), 100- seed weight (3.5 g), and oil percentage (17.9%) belong to May 5th + 40 plants per m2. by delaying planting time, 100- seed weight causes oil percentage to drop and the seed yield (40%), galactomannan (68%) and the oil percentage (15%) are observed in September.  Therefore, it seems that the best time and density for planting Alyssum is May 5th with a density of 40 plants per m2.

Among all weeds, cogongrass (Imperata cylindrica L. Beauv) has been identified as a problematic weed in the sugarcane (Saccharum officinarum L.) fields of Iran for over 20 years since 1996. Failure to control of cogongrass regrowth during spring develops it rapidly and, in turn, reduces the sugarcane yield in subtropical Iran. In effect, the identification of weak points in cogongrass phenology and frequency is deemed to help decision makers adopt effective controlling strategies in optimum time. Storage of carbohydrate reserves by plants is, in turn, the best mechanism for optimizing the timing of management strategies when reserves are at the lowest levels in storage organs. Glyphosate has been also widely used in Iran to control of weeds in the sugarcane fields. Currently, despite double spraying, the spring control of cogongrass is not satisfactory in the sugarcane fields in subtropical Iran.

Two studies were carried out in Salman Farsi Agro-Industrial Company in about 40 km south-west of the center of Khuzestan Province, Ahvaz, Iran, in 2017. In the first experiment, monthly (February–November) total nonstructural carbohydrate allocation patterns of cogongrass were evaluated to determine carbohydrate low points in the seasonal phenological cycle. To that end, glyphosate (00, 0.92, 1.84, 2.76 and 3.68 L a.i ha-1) was applied in April and June, 2017, in a 10×2 factorial design under randomized complete block designs with four replications. Data were analyzed using standard ANOVA procedures with the subsequent use of Least Significant Difference test (Little and Hills 1978( to separate means.

The occurrence of carbohydrate low points (CLPs) (88.69±13.15 mg g-1) was considered from May to August, CLP was found to have two important points with the potential control of cogongrass reported. The first and second points were in May (579 GDD) and August (2683GDD), respectively. The suppression of cogongrass (58-100%) was achieved with the three highest rates (1.84, 2.76 and 3.68 L a.i ha-1) in both application times, although substantial regrowth occurred in all plots by 5 months after the first treatment.

Double spraying with a 60-day interval did not result in the effective control of such a troublesome weed in the sugarcane fields. Applying glyphosate two times in the spring and mid-summer (the end of CLP, 2683 GDD) was determined effective for the long-term control (6 months) of cogongrass. The results suggest that glyphosate 1.84 L a.i ha-1 should be performed on cogongrass in the spring for improved control.

One of the important factors in the adaptation of plants to new environmental conditions is the appropriate response of development stages to temperature and photoperiod regimes. The thermal time, growing degree days (GDD) or heat unit concept is commonly the basis for modeling phenological development in crop models for different common crops and under-utilized crops. The GDD concept describes crop development as a function of temperature accumulation above the base temperature (lower limit) and in some cases below a cut off temperature (upper limit). Evaluation of plant photoperiod sensitivity is often beneficial help to use appropriate cultivars which in turn to ensure cultivation success. Considering that adaptation of quinoa to new regions demands acclimation to appropriate temperature range also day-length, this study aimed to investigation of quinoa response to Yazd weather condition as an arid region to assess the possibility of quinoa cultivation under these conditions.

This research was conducted through 10 separate experiments and were based on a randomized complete block design with three replications. The experimental treatment consisted of five lines (1, 2, 3, 4 and 5), and one cultivar (Titikaka) which belong to different maturing groups including early, middle and late maturing. Ten planting dates selected to be serial as following: March 29, April 29, May 28, June 28, July 26, August 23, September 6, September 20, January 29, and February 29. Every three days, phenological stages of each line including planting distance to each stage of development including emergence, four leaves, flower bud, panicle formation, pollination, seed filling, seed hardening and ripening were recorded accordingly. Using local weather data and equation 1 the needed GDD for every development stage was calculated:GDD= (Tmax-Tmin)/2-T(1)MS-Excel Ver. 15 was employed to arrange recorded data and required calculating. Fitting equations and plotting the graphs were done using Slide Write Ver. 2 and Minitab Ver. 20 software.  

The results showed that the mean of flowering temperature up to seed formation stage was between 25 and 30 °C for five lines and was between 20 and 25 °C in cultivar 6. The mean length of photoperiod for flowering and seed formation stage of these lines was between 12 and 12.5 hours. The relationship between temperature and day length was inversely related to the number of days of flowering stage, i.e., with decreasing day length and increasing temperature, the number of days for flowering stage was increased. The time required for flowering stage, between 20 to 30° C, for the early maturing cultivar was about 35 days, for the middle maturing lines including 1, 2, 3 and 6 was about 40 days and for the late maturing line 4 was about 45 days. At temperatures higher than 30 °C, a decreasing trend was observed in the number of days required for flowering stage. From the budding stage to the end of the growth period, a significant difference in the GDD was observed for the quinoa lines. The GDD of quinoa was the highest (2530 °C) for late maturing line (4) and was the lowest (1805 °C) for the early maturing cultivar. The effect of planting date on the GDD of quinoa lines showed that moving from March planting date to July, there was an increasing trend on the GDD of quinoa lines and by moving from July planting date to October, a decreasing trend was observed.

In general, quinoa is a short-day plant which is affected by the day length from flowering to seed maturity stages. Line 6 responded qualitatively to day length; however, the other lines responses were quantitatively. The study of the simultaneous effect of temperature and day length showed that temperature has a compensatory effect for day length during flowering stage. According to the results, it seems that the most suitable planting date for early lines suggests in September, for middle maturing lines suggests in August and for late maturing lines suggests in August. The results also showed that line 6 is more suitable than other lines for cultivation in cold regions.

The present study has been conducted to investigate the duration of growth period of different cannabis (Cannabis sativa L.) ecotypes and their responses to water stress based on a factorial completely randomized experiment design in the greenhouse condition at the University of Tehran in 2017. Irrigation levels include 50%, 75%, and 100% of field capacity, with the ecotypes being Urmia, Sanandaj, Tabriz, Dasht-e-Moghan, Rasht, Khomein, Daran, Qom, Shahroud, Kerman, Tabas, and Saravan. Results show that Rasht and Khomein ecotypes have had the highest and lowest duration of germination phase and growth degree-days (GDD1), respectively. The highest duration of vegetative, flowering and maturation phases belong to Dasht-e-Moghan, Rasht, and Dasht-e-Moghan ecotypes with 71.33, 30, and 46.66 (days), respectively, at 100% field capacity. The lowest durations of these phases could be seen in Tabas, Tabriz, and Saravan ecotypes with 42, 16, and 17 (days), respectively, at 50% field capacity. Also, the highest values of growth degree-days for vegetative (GDD2), flowering (GDD3), and maturation (GDD4) phases  for Dasht-e-Moghan, Kerman, and Dasht-e-Moghan ecotypes with 1788, 836, and 1169 (0C.d), respectively, at 100% field capacity, with their lowest values belonging to Tabas, Tabri,z and Saravan with 1039, 413, and 448 (0C.d), respectively, at 50% field capacity. Based on growth period duration and cumulative growth degree-days (total GDD), Tabas and Dasht-e-Moghan ecotypes are found as earliest and latest ecotypes, respectively.

Temperature based agro-meteorological indices such as growing degree days and helio thermal unit have been reported quite useful to predict the growth and yield of crops. The efficiency of converting heat and radiation energy to dry matter depends on the genetic factors, sowing date and crop type. Hence, the knowledge of calculation heat thermal summation unit, mostly called the growing degree days and its further mathematical derivations like helio thermal unit and heat and radiation use efficiency will be the basic prerequisite of phenology periods and optimum planting date for different crop varieties. In spite of much researches have been done about onion in country, no paper have already published related to study the agro-meteorological indices at phonological stages of this crop. This experiment was conducted to study the effect of planting date on agro-meteorological indices at phenological stages and yield of Behbahan bred onion.

This research was conducted in randomized complete block deign including four planting dates from 6 September to 21 Octobers with 15 days interval contain four replications at Behbahan Agriculture Research Station for two years (2014-16). In this experiment studied genotype was Behbahan bred onion. Seedlings were transplanted (at two or three leaf stage). Fertilizers were applied based on soil analysis results according the recommendation of Soil and Water Research Institute.Time of bulbing was estimated based on bulbing ratio and cumulative sums. Agro-meteorological indices including growth degree days, helio thermal unit and photo thermal index were calculated at seed germinations, vegetative growth and bulbing and bulb development stages. Bulbs were harvested when 50-80% of foliage top had fallen and collapse. Statistical analysis was performed using MSTATC software and mean comparisons were also performed using Duncan’s multiple range test at P≤0.05.

The lowest duration between plant to seedling emergence and minimum growth degree days at seed germination stage were appointed to planting date at 6th September. The maximum photo thermal index during seed germination stage belonged to 21st September and 6th Octeber planting dates in the first and second year of experiment, respectively. The maximum growth degree days and helio thermal unit during transplant production belonged to 21st September planting date as well as with delaying planting date these indices decreased. The differences of obtained growth degree day in all studied planting dates were not considerable in plant growth period (Except of sowing date at 6th October in the first year) during two years. The highest yield, thermal use efficiency and helio thermal ones were recorded for 6th and 21st September planting dates in the first and second year, respectively. Reduction of growth and development of bulb in sowing date at 21st October and being exposed to high temperature at the late of this stage led to produce the lowest yield at this planting date.

According to the results, the best planting date is 21st September for Behbahan bred onion and delaying sowing date caused in yield reduction.

Growing degree days (GDD) and helio thermal units (HTU) are the temperature based agro-meteorological indices that play important role in predicting crop growth and yield. Growing degree days is based on the concept that the actual time to achieve a phenological stage is linearly related to base temperature (Tb) and optimum temperature. The efficiency of conversion of heat and radiation energy to dry matter depends on genetics factors and planting date. Heat summation units (HSU), that mainly called growing degree days, and its derivations such as helio thermal units are the most necessary to determine phenological stages and the suitable planting dates for cultivars of different crop. Growth of potato can be divided into five stages: sprout development, vegetative growth, tuber initiation, tuber bulking and maturation. There is little information concerning of growing degree days and helio thermal units for potato in the sub-tropics. This experiment was undertaken to define growing degree days and helio thermal units at phenological stages and effect on yield for potato cultivars established at different planting dates.

The research was conducted in the research farm of Behbahan Agriculture Research Station for two years (2015-2017). The experiment was arranged as a split-plot in a randomized complete block design with three replicates. Planting dates from 21 December to 20 January at a 10-day interval were the main plot and the Cozima, Savalan, and Elmera cultivars were considered as sub-plot. When the diameter of the swollen tip of stolon was twice as long as stolon diameter, considered as tuber initiation. Tubers were harvested in mid May. Growing degree days and helio thermal untis were calculated at all phenological stages and after harvest thermal use efficiency and helio thermal unit use efficiency. Results from experiments of 2 years were combined for analysis. Data were statistically analyzed by MSTAT-C. Significant differences among treatments means were determined at p ≤ 0.05 by Duncan’s multiple test range.

The longest of the sprout development stage was recorded for 21 Dec. planting date. With the postponement of planting date, due to increase temperature, duration of sprout development significantly shortened, and growing degree days and helio thermal unit decreased. The duration of vegetative stage was 15 days. Early exposure of plants to favorable climatic conditions for tuber initiation, short day and cool night temperature, caused the duration of vegetative growth, growing degree days and helio thermal unit were low. Tuber initiation is thought complete within 2-6 weeks of that event, but since the majority of the tubers are formed over a period of 15 days, duration of this stage is usually considered about 15 days. Although the duration of tuber initiation was equal in all planting dates, however there was significant difference between the amount of growing degree days and helio thermal unit in some treatment dates due to unsimultaneous timing of tuber initiation. The duration of tuber bulking, depend on planting date and cultivar, ranged from 38 to 44 percent days. Growing degree days and helio thermal units at tuber bulking stage were higher than previous stages, such as depend on planting date 61.52 to 66.27 percent of total growing degree days belong to tuber bulking stage. Maturation stage was not observed. There were no significant differences for yield and helio thermal unit use efficiency among all planting dates, however the highest thermal use efficiency was recorded in 20 Jan. planting date. The highest yield, thermal use efficiency and helio thermal units use efficiency belong to Savalan cultivar. Climatic conditions at sprout development, vegetative growth and tuber initiation stages were relatively more favorable for Savalan cultivar in 20 Jan. than other planting dates. Moreover, plants of Savalan cultivar in 20 Jan. planting date, during incidence of late blight in effect of less age were more tolerant as compares with other planting dates. Therefore, the yield of Savalan cultivar in 20 Jan. was significantly higher than other planting dates.

The duration of sprout development and vegetative stages are long and short respectively. In this experiment low temperature during sprout development and high temperature from mid tuber bulking stages caused the less tuber yield than temperate regions of the country. According to results, planting of Savalan cultivar in mid January is recommended for winter potato production in Khuzestan province. Planting from mid December to mid January is recommended for Cozima and Elmera cultivars.

This study was conducted as split-split-plot based on randomized complete block design with three replications at experiment station of the Agricultural Faculty of Bardsir, Shahid Bahonar University of Kerman at 2018. The experimental treatments were planting date (5 April, 5 May and 5 June) assigned to main plot, irrigation levels (90, 60 and 30% of filed capacity) as subplot and foliar application (salicylic acid 1 mM and water) as sub-subplot. The results showed that the delay in planting date shortened the Quinoa growth period. GDD and growth period were decreased by drought stress. May planting date has significantly higher root length (31.81 cm) and dry weight (9.09 g plant-1) than two other planting dates. The highest root length for April (28.27 cm) and May (35.92) planting dates was assigned at 60% of FC, while for June (21.27 cm) was related to no-stress condition. Averagely, grain yield for May (653.91 kg ha-1) planting date was significantly higher than April (578.7 kg ha-1) and June (460.8 kg ha-1). Decrease in consumed water to 60% of FC had no significant effect on grain yield, but the trait value in 30% of FC was significantly lower than other irrigation levels. Justly at severe drought level, grain yield was significantly increased by foliar application of salicylic acid than water application. Relationship of grain yield was positive with grain oil percentage (r = 0.82) and was negative with protein percentage (r = -0.78). Water use efficiency (WUE) was significantly higher in May planting date than in April and June planting date. WUE increased significantly with water consumption decreasing. Generally, the results illustrated that May planting date is the most suitable planting date for Quinoa in Bardsir regions and same climates. Results showed that the plant has a considerable tolerate in water stress condition.

In studying the phenological stages of crops, the growing degree-days (GDD) gradients is considered as an alternative to counting the calendar days. Genetic diversity of 86 Iranian cultivars and 184 Iranian wheat landraces were studied based on the phenological stages (day to booting, day to flowering, day to maturity and GDD of these stages) along with grain filling period, thousand grain weight and grain yield during the 2013-14 and 2014-15 growing seasons. The results revealed that there is a significant difference between cultivars and landraces and studied traits were able to effectively distinguish between cultivars and landraces. On the other hand, the results indicated that genotypes with different growth habits have a significant difference in terms of most of the phenological traits. That is implied that either directly or indirectly has been occurred on increasing the length of the grain filling period along with grain yield. Since the diversity of phenological traits was higher in landraces, they can be a valuable source of choice for improving these traits. Finally, due to the importance of the phenological stages, it is recommended that these traits be taken into account in terms of yield and yield components and GDD index can be used to obtain more accurate results.