جستجوی مقالات مرتبط با کلیدواژه "growth-degree day" در نشریات گروه "زراعت"

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.

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.

To evaluate the climatic impacts and future climatic changes on geographical distribution of the Dodartia orientalis, an invasive weed species in the world and Iran, a study was conducted in Ferdowsi University of Mashhad, using CLIMEX software, during 2016. The results represented that the plant species has a distribution potential in the world towards east china, most east European countries and central states of USA. So that the regions relies in the geographical position of 35 to 55 northern altitude which gradually will extend towards the higher northern altitude that leads to limited continental spread of the plant to Africa, Australia and south America. The distribution pattern of the weed in Iran was found mostly in North, Razavi, and South Khorasan, , Kohkiloyeh, Chaharmahal, Fars, Lorestan, Ilam, Kermanshah, Hamedan, Central and Tehran provinces which will be highly expanded towards the country North West provinces as a result of the occurrence of climatic changes. Therefore to manage this weed, while taking steps towards its quarantine; further studies on the control methods and tools to restrict its establishment, development and expansion should be conducted in vulnerable countries at risk.

In order to evaluate the effect of autumn and winter planting on yield and phenology of potato cultivars using thermal indices an experiment was coducted in split plot in time based on a radomized compelet block design with three replications at Behbahan Agriculture Research Station in Khuzestan province, south of Iran in 2014 and 2015. Cultivar (Sante, Savalan and Javid) was considered as main plot and planting season (autumn and winter planting) as sub plot. In Autumn and winter planting seasons tubers were planted in early October and early December, respectively. Tubers were harvested in early March and mid May in autumn and winter planting seasons, respectively. The duration of sprout dvelopement in the autumn planting season was 14 days shorter than winter planting season, but tuber bulking duration was 25 days longer in the latter planting season. Futhermore, growing degree days, helio thermal unit and photo thermal index of sprout development stage in autumn planting season (117.41°C day, 1967°C day hour and 9.29°C day day-1, respectively) were greater than winter planting. However these agro-meteorologial indices at tuber bulking stage (537.58°C day, 4168.79°C day hour and 10.42°C day day-1, respectively) were smaller in winter planting. Yield, thermal use efficiency and helio thermal use efficiency were reduced (18.36, 34.95 and 31.58%, respectively) due to high temperatures encountered during tuber bulking stage in winter planting as compared with the autumn planting season. The highst yeild, thermal use efficiency and helio thermal use efficiency in both of planting seasons belonged to Javid cultivar.

In order to study the effects of sowing dates on some morphological and phenological characteristics and yield of safflower (Carthamus tinctorious L.) cultivars, a field experiment was conducted in Azad University of Birjand Research Farm during growing season of 2006-2007. The experiment was done as split plot based on completely randomized block design with three replications. In this study four sowing dates (15 Oct, 30 Oct, 15 Nov, 30 Nov) were used as main plots and three varieties (local Isfahan, Zarghan and LRV) were as sub plot. Results showed that, plant height, number of branches per plant and height of first flowering branch from ground level, were affected significantly by sowing date. Also, effect of sowing dates on duration of seed emergence, stem elongation, blooming, flowering and ripening was significant. With delay in sowing date, duration of all phenological period decreased. Maximum grain yield (1209kg/ha) was obtained in the first sowing date and when delay to 30 Nov, grian yield decreased about 56.5 percentage. Effect of cultivar on some traits such as plant height, number of branches, height of first flowering branch from ground level and grain yield was significant. Duration of seed emergence was affected significantly by cultivar. Interaction effects between sowing date and cultivar were significant for all traits, except duration of plant height, number of branches per plant, seed emergence, blooming and ripening. According to these results, maximum grain yield obtained from 15 Oct sowing date and LRV cultivar.

In order to investigate the effects of sowing date on yield, yield components and oil yield of flax (Linum usitatissimum), an experiment was conducted based on randomized complete block design with three replications at Shahid Chamran University of Ahwaz, Iran during 2012- 2013. Sowing dates were 5 December, 25 December, 14 January and 3 February. The results showed that all traits decreased with delay in cultivation. The highest plant height (79.33 cm), number of main branches in plant (3.33), number of capsule in plant (33.66), number of seed in each capsule (8.96), 1000 seed weight (5.30 g), seed yield (1349.67 kg. ha-1), harvest index (37.33), oil percent (37%) and oil yield (497.77 kg. ha-1) obtained in first sowing date. The growth analysis showed that leaf area index, total dry mater, relative growth rate (RGR) and crop growth rate (CGR) declined delaying in cultivation. Generally, cultivation of falx is recommended on 5 December under Ahvaz condition.

To evaluate the competition effect of cotton planted in different row spacings on growth, leaf area and its vertical distribution in canopy of velvetleaf an experiment was conducted in a completely randomized block design with split plot arrangement of treatments with three replications at Experimental Station of Gorgan University of Agricultural Sciences and Natural Resources during 2011 growing season. Result showed that maximum velvetleaf leaf area index with 6.1197, was obtained in plot of 12 plant /m-2 density and 80 cm cotton row spacing. 50% of maximum velvetleaf leaf area index was achieved after 1229, 1067.1 and 1219.8 growth degree day in 20, 40 and 80 cm of cotton row spacing, respectively. According to result of vertical distribution of leaf area study, maximum cotton leaf area in UNR, was observed in 5 plant.m-2 weed density and the most of this leaf area, with 27586.4 cm-2, was distributed at 75 cm cotton height. Maximum velvetleaf leaf area was observed in cotton planted in ultra narrow row (UNR) and 12 plant /m-2 weed density; the maximum amount of leaf area in this condition with 20870.34 cm-2 was distributed in 175 cm velvetleaf height. In contrast, in conventional row (CR) system the maximum velvetleaf leaf area was observed in 12 weed plant /m-2, and the maximum leaf area in this condition, with 34351.18 cm-2, was distributed at 225 cm velvetleaf height. In CR system, maximum cotton leaf area was obtained in no weed plant /m-2 and maximum produced leaf area in this condition, with 21658.5 cm-2, was distributed at 100 cm plant height.

Berseem clover is one of leguminoes forage crops which its yield performance depends on interactions among climatic, genetic and agronomical factors. This investigation was carried out in Karaj region to determine the growth degree days of different growth stages and seed and forage yield production of Berseem clover in four planting dates (16 March, 4 April, 25 April and 15 May). The results showed that 1060 (68 days) and 503 (25 days) GDDs are needed for forage production in the first and second cuts, respectively and 2000 GDD (120 days) for seed production. Among the different growth stages, branching and anthesis stages were the longest (31 days) and the primary leaf stage was the shortest (3 days) periods. The results demonstrated that the period from planting to the first cut was 75 days in the first planting date (the longest period), and 65 days in the third and forth planting dates (the shortest period). Although the longer period was needed to reach the first cut at the first planting date, its GDD (877 GDD) was lower than those of the third and forth planting dates (1132 and 1256 GDD respectively). This period was 25 days in all planting dates, but the GDDs accumulated during this period were 503.2 GDD. In general, Berseem clover needs 1563 GDD (93 days) for forage production with two cuts and 2000 GDD (120 days) for seed production. Based on these results, early planting date is recommended for forage and seed production.