جستجوی مقالات مرتبط با کلیدواژه « gdd » در نشریات گروه « زراعت »

The increase in global temperature predicted by several climate models has a direct impact on plant growth, yield, and cotton quality. This type of temperature change in agriculture can be produced by planting crops at different dates and growing crops under different temperature and humidity conditions. The objective of this research is to model the evolution of phenology in commercial cotton varieties using meteorological parameters.

To determine the required GDDs of commercial cotton varieties under different planting dates, field experiments were conducted in 2018 in two regions, Hashem-Abad (Gorgan) and Karkandeh (Kordkoy). To estimate the effects of planting date on phenology, field experiments were conducted using a split-plot design with 6 planting dates (15 days apart) as the main plot and 3 cultivars (Golestan, Latif and Sajedi) as subplots with 3 replicates. Data analysis was performed using SAS software and Excel software was used to prepare the graphs.

The results showed that the effect of planting date on days required from planting to boll opening was significant at p = 1% in both Karkandeh and Hashem-Abad. Thus, with a delay in planting date, the number of planting days to emergence increased from 7 and 9.1 to 4.6 and 3.1 days in both Karkandeh and Hashemabad, respectively; to the budding stage from 52 and 46 to 29.2 and 23.2 days, respectively; to flowering from 63.3 and 57.9 to 41.9 and 33.3 days, respectively; to flowering from 75 and 63.8 to 58.The results of yield comparison showed that the highest yield of total cotton (4015 kg ha-1) was associated with the second planting date among the employees and in Hashemabad the highest yield of total cotton (4122 kg ha-1) was obtained with the third planting date.

The results of this study showed that the GDD required for cotton cultivation was significantly different among the different planting dates.

Hedge parsley(Torilis arvensis)is an annual weed from Apiaceae family, which is considered as a weed of summer crops in Iran. This experiment was conducted to investigate the phenology of this weed at the research farm of the Faculty of Agriculture, Razi University of Kermanshah. Weed seeds were cultivated every two weeks from February 21, 2018 to May 1, 2018. The phenological stages were recorded from emergence to the end of seeding stage, including emergence, stemming, flowering and starting and completing the seeding. At the end of the experiment, the period of each phenological stage was calculated based on the day and the growing degree day. The results showed that the shortest and longest stages of development of this weed were from flowering to starting the seeding (7.6 days) and emergence to stemming (50.4 days). The results also showed that Torilis arvensis is a spring weed that completes its phonological stages in 178 days (equal to 1975.6 growing degree days). The results show that the best time to control this weed is late spring (before flowering).

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.

Scrophularia striata is an originally Iranian wild perennial plant. This plant has many medicinal properties including treatment of some diseases like cold, digestive disorders, inflammation and infection. Although S. striata has been reported from various regions of the country with different climatic conditions, however there is no information about phenological growth, suitable time and seedbed of S. striata. There are variety of environmental factors that affect phenology growth. Among them temperature is considered as the most effective one. To generalize prediction of phenological growth in different locations, standard measurement is required. Growth degree day (GDD) or thermal time can be a consistent predictor of phenology development in contrasting climates. Determining required thermal time for plant phenological development would provide information for decision making on the time of management practices including planting date, timely irrigation and efficient pest and weed management. To the best of our knowledge there is no information about plant establishment, growth and phenological stages of S. striata. Because of its high demands for medicinal products, information about the S. striata cultivation is necessary. Therefore the objective of this study was to determining the effect of planting time and seedbed on phenological growth. Field experiment was conducted in experimental farm of agricultural and natural resources college, university of Tehran, Karaj during 2016-2017. Seeds were preconditioned at temperature of 3ºc for one week to break dormancy. For seedling establishment, seeds were transferred to the greenhouse and cultivated in three different seedbeds. Seedlings were transferred to the farm at stages of four to six leaves. The experiment was a split plot with three replications. Planting dates comprised Early June (D1), September (D2), October (D3) and November (D4) of 2016 and Early March (D5) of 2017 were the main plots and seed beds of peat moss, peat moss+ perlite (1:1) and coco peat+ peat moss+ perlite (2:1:1) were the sub plots. Growth Degree Days (GDD) for phenological stages of S.striata including first and second node, flowering, capsule formation, seed formation and maturity were calculated. Data were subjected to ANOVA using SAS 9.1, and standard error of means was calculated. Results showed significant main effects and interactions between seed bed and planting date at 1% probability level on phenological growth of S. striata. Peat moss seed bed with June planting had lowest GDD to first node (39.5 GDD), second node (50.1 GDD), flowering (307.4 GDD), capsule formation (610.8 GDD), seed formation (697.8 GDD) and maturity (1242.0 GDD). With delay in planting time to September, October and November, GDD requirements for phenological growth increased. Between our planting dates, June planting time was the most suitable time for planting. Changes in temperature, day light and precipitation are significant in successful plant establishment and growth. Our results showed that there is a critical time for planting S. striata in farm. Very early planting like March planting time was not good and plants did not enter the reproductive stage. Plants of June planting time were entered flowering stage on April 15 in the next year. With delay in planting time to November, plants entered flowering stage on May 10 in the next year. High organic matters percentage and capacity of cation exchange provides increasing potential for water absorption and keeping nourishing elements and water for a longer time. This causes improved conditions for root growth. In addition, vermicompost and peat moss includes regulator hormones such as humic acid that benefits early growth of plant. To conclude, 1) peat moss was recognized as a successful bed for initial growing of S. striata. To the best of our knowledge, no practical recommendation was formerly provided on the subject. 2) June planting time was determine as the best time for plant establishment that led to acceleration in flowering time and more seed production.

Climate change can affect the crop yield and water consumption in agriculture by changing duration of phenological stage, crop yield and evapotranspiration. In this research a number of GCM models were selected and forecasted annual mean temperature of the region was validated. The climate models forecast 2 to 5 °C by the end of this century in Zabol. Therefore, three temperature scenarios (zero, +2 and +5), representing no temperature change, the minimum temperature increasing and the maximum temperature increasing, respectively were added to the observed data temperature. The effect of climate change was examined on duration the growth season and phonological stages of wheat (Triticum aestivum), as well as evapotranspiration in Zabol based on planting date and conventional variety. The GDD method was used for calculating the phonologic stages. Hargreaves – Samani model was used for measuring the effect of climate change scenarios on evapotranspiration. Results showed that 2 °C increasing temperature by the end of the century reduced growth duration of wheat by 14 days compared to no temperature change. In addition, early growth evapotranspiration decreased by 20 percent. Increasing 5 °C decrease growth duration of wheat by 32 days and increasing early evapotranspiration by 46 % growth in region. Climate change influenced wheat culture in region. Coping with these changes require planning for production components change according to today's conditions or define new conditions based on adaptive patterns.

IntroductionNowadays technological innovations, the use of chemical inputs, development of methods and etc., help agriculture to produce food for human. However, some problems such as growth in fertilizer prices and environmental pollution has drawn attentions to sustainable agriculture.
Sesame as the oldest known oil-seeded plant by mankind has ranked #9 among 30 important oil seeds. Therefore cultivation of this valuable plant should be done based on ecological principles and inputs.
Growth and phenological aspects of sesame affecting by bio-fertilizers is less known. Therefore, the aim of this experiment was to evaluate the growth and phenology of sesame by application of various biological and chemical nutritional sources.
Materials and MethodsThis experiment was conducted in randomized complete block design (RCBD) with 3 replications and 10 treatments including Nitroxin® (Ni), Biophosphor® (BP), Biosulfur® (BS; with recommended amount of elemental sulfur), double mixture of Ni, triple mixture of Niӿ, Urea (U), triple super phosphate (P), double mixture of U, triple mixture of U plus the used amount sulfur in BS, and control.
Sampling was conducted every 7 days and growth indexes including, leaf area index (LAI), total dry matter (TDM), crop growth rate (CGR), relative growth rate (RGR), net assimilation rate (NAR) were studied during growth life of the crop. Phenological stages were recorded then GDD was calculated for different phenological stages. Statistical analysis and drawing of figures were performed using Minitab and MS Excel.
Results and DiscussionA. Growth Indexes: Changes in LAI, TDM, CGR, RGR, and RGR under all treatments were almost similar. during the early days of growing, LAI increased gradually and then it rose sharply after production of more leaves by the plant in most of the treatment about 35 days after sowing. After the flowering stage, by lowering of increase in LAI, all of the treatments reached to their maximum LAI and then decreased. Control and BS had minimum LAI (2.42 and 2.54) among all treatments. LAI of U㿤 and U were highest LAI (3.42 and 3.32 respectively) and after it, Niӿ (3.03) and Ni (3.01), urea (2.98), Nitroxin (2.85), Biophosphor (2.75), triple superphosphate (2.78) were placed respectively.
The highest dry matter accumulation occurred in plots that meet higher LAI, resulting in a higher potential for the production and accumulation of dry matter. So, the highest dry matter accumulation was recorded in U㿤 and U, and then Niӿ and Ni and urea.
Due to the development of leaves and roots, CGR increased and then reached to its highest amount after 52 to 70 days from the sowing. Then, about 100 days from sowing, CGR decreased and this trend continued to the end of plant life. Application of Nitroxin and Biophosphor increased CGR of sesame, but it did not affect CGR of Biosulfur treatment. The double and triple mixture of biofertilizers and chemical fertilizers increased the growth of sesame in comparison to their sole application.
Numeral amount of RGR was between 0 to 1 that describes the amount of increase in plant dry matter weight in order to its previous dry matter’s weight among a time period.
In all treatments, NAR at the beginning of the growing season due to low levels of leaves and photosynthesis were low. Gradually in the middle of the growing season, NAR increased, along with the increased growth of plants and their LAI. Because of some reason remobilization and aging of the leaves and reduction of the efficiency of photosynthesis, NAR has an intense reduction. All the treatments had higher NAR comparing to control.
B. Phenological Stages: Statistical analysis of data showed that the effect of treatments on phenological stages was not significant. But seeds in the treatments of biofertilizers grew 3 days earlier in average. It has been proven that farm managerial decisions that cause faster growing of plants (even one day), can be effective in competitions of crops versus the weeds.
ConclusionsBased on the results, it can be concluded that although nutrition resources affected the sesame growth indexes, they had no effect on phenological stages of sesame.

An experiment to investigate wheat and wild barely phenology was conducted during 2008-2009 in the field of Plant Protection Research Institute in Varamin. Wild barely and wheat (Variety Kavier) were planted in the vicinity of each other in a randomized complete blocks design with four replications. Phenological stages based on international Zadoks scale and GDD based on growing degree days were calculated for each stage of growth. Results showed that wild barely finished its phenological stages faster than wheat. Thus, complete life cycle of wild barely required 1839/1 growing degree days and 204 days, while wheat needed 2143/1 growing degree days and 219 days. At wheat maturity seeds stage, wild barely seeds had completely fallen except for the final seed clusters. Wild barely seed dormancy period was about 45 days. Comparative study of phonological stages of wild barely and wheat showed that the plants grew together of early stages, of growth up to early tillering, from then to the end of tillering, wild barely surpassed wheat. However, in the stem elongation stage wheat surpassed wild barely. However wild barely started inflorescenc emergence sooner than wheat. Our results suppots the idea that success of wild barely to infest wheat fields is due to rapidly reaching full maturity and short seed dormancy period.

Winter weeds have different emergence flashes in field and response to this question whether there is flash emergence after applying herbicide, can be effective in the selection of right time for weed control. Therefore, emergence pattern of the wild oat seedlings was studied for three years from 2011 to 2014 in cereal fields of Fars province. The cumulative emergence pattern of wild oat during 2011-2012 showed that 50% of emergence occurred at growing degree days (GDD) of 115. The emergence percent revealed that 21.09, 45.00, 19.37 and 2.43% seeds respectively at GDD of 99.25, 136.75, 180 and 220 were emergence. The emergence pattern in 2012-2013 crop years also showed that a GDD of 127 was required for 50% emergence. This amount for 2013-2014 crop years was 146 GDD. With regard to the contamination and presence of wild oats in the fields, final results of this study showed that the hypothesis of various flashes after the herbicide application is rejected. All the weed seedlings emerge in in fields during the first month after planting.

In order to create different environmental conditions and to estimate the required growth degree days (GDD) and heat units (CHU), fourteen foreign and Iranian potato genotypes in three different maturity groups were evaluated in two regions, Shako Mountain, and plain region for three cropping seasons (2007-2010). The results revealed that both systems, i.e. GDD and CHU changed maturity group of some of the genotypes based on heat requirement during emergence and flowering. Some genotypes such as 397007-11 and Sante were grouped as the late matured compared to the previous grouping based on IBPGR. Year and year by genotype interaction effect were significant in both locations. Years with higher air average temperature increased the heat index 1200 (GDD) and 4000 (CHU) in the mountain region of Shahkooh whereas in the plain region of Gorgan GDD and CHU increased 1000 and 2000, respectively. Genotypes 397009-3 could be considered as the best genotype because of producing the highest tuber yield (27003 kg ha-1) in autumn and spring cropping (28446 kg ha-1), with production of 12.5 and 11.9 tuber plant-1 in autumn and spring cropping, respectively. Based on the information available about the maturing groups according to IBPGR and the time of the phonological stages during evaluation of these genotypes, the grouping based on GDD seemed more logical.

Knowledge about weed seedling emergence pattern provides helpful information to improve management decision making. Emergence pattern is genetically controlled and built up in association with environmental conditions. Six Hordeum spontaneum Koch populations that collected from different climates around Iran، were sown in field in a complete randomized block design with 4 replications. Seedlings were counted using the fixed quadrates at 3-day intervals until no emergence occurred in field. Cumulative emergence against thermal time (GDD) was described with sigmoid function for each population. Parameter estimates indicated appearance of populations in field with different patterns. Kermanshah population was the first seedlings emerged receiving 67 GDD followed by Khorasan Razavi populations which emerged 2-weeks later (76. 6 GDD). Tehran and Ghazvin populations showing similar pattern appeared in field at GDD of 76. 6. Fars and Khozestan were the last populations emerged in field with receiving 83 and 88 GDD، respectively. There are significant correlations between emergence patterns and climate conditions form which the populations were collected.

The current study was carried out to examine sugar beet growth pattern in climatic conditions of Hamedan, Iran and to recognize the factors affecting its quantity and quality as well as the physiological indices. Two sowing date experiments were conducted on the basis of a Randomized Complete Block Design with four replications and 11 harvests. The plots were destructively sampled and the growth was analyzed by regression method on the basis of the variations of leaf area index, leaf dry weight and total dry weight which are the basis of growth analysis. Results revealed that the maximum crop growth rate of the earlier sowing date reached to 20.2 and 23.3 g.m-2.d-1 90 days after planting in 2002 and 2003, respectively. In the second sowing date, maximum crop growth rate reached to 29.5 and 25.0 g.m-2.d-1 110 and 96 days after planting in 2002 and 2003, respectively. Maximum leaf area index of the earlier sowing date was obtained about three months after planting approximately concurrent with the realization of maximum crop growth rate and reached to 2.5 in 2002 and to 2.6 in 2003, but it started to slowly decrease at later growth period. Relative growth rate was the highest at the early growth period and linearly decreased during growth period. Net assimilation rate firstly increased slowly, but as the leaves grew and shaded each other, it started to decrease. The highest root growth rate in the earlier sowing date reached to 10.1 and 20.0 g.m-2.d-1 94 and 92 days after planting in 2002 and 2003, respectively. The highest root growth rate in the second sowing date reached to 14.0 and 17.3 g.m-2.d-1 108 and 95 days after planting in 2002 and 2003, respectively. In total, root potential yield was considerably higher in the earlier than in the delayed sowing date under climatic conditions of Hamedan in both years. The sugar beet growth pattern-related physiological indices were greatly consistent with crop yield potential during growing season. Therefore, given the climate changes and global warming, sugar beet sowing in the earliest possible date in Hamedan is recommended in terms of physiological indices and yield.

An expiment was conducted in Lorestan Province to investigate the effect of different densities (0, 1, 2, 4, 8, and 16 plant/ m2) of Ground cherry in sugar beet yield. Experimental design was complete randomized design with three replications. In another experiment the effect of single was evaluated on neighbor sugar beet plants. Results indicated that 2 Ground cherry plants can reduce sugar beet yield as much as 34%. A single Ground cherry plant affects sugar beet plants as far as 50 cm away. When planted adjacent to sugar beet Ground cherry reduces the growth of sugar beet plants by 41%. Ground cherry seems to flower in mid May when acquired about 61 to 75 degree days.