Fatemeh Ghobadi; Nasser Majnoun Hosseini; Mostafa Oveisi; Gholam Akbari
Abstract
To investigate the effect of different levels of irrigation and nitrogen fertilizer on yield and yield components of some safflower cultivars, an experiment was conducted as a split-split plot in a randomized complete blocks design with three replications in the research farms of the University of Tehran, ...
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To investigate the effect of different levels of irrigation and nitrogen fertilizer on yield and yield components of some safflower cultivars, an experiment was conducted as a split-split plot in a randomized complete blocks design with three replications in the research farms of the University of Tehran, Karaj during 2018-2019. Main plots were irrigation (normal irrigation, irrigation until at middle of flowering stage and irrigation until the beginning of seed filling), sub plots were nitrogen (supply of 100 % and 50 % of nitrogen needs) and sub-sub plots were safflower cultivars (Goldasht, Golmehr, Padideh and Parnian). The effect of irrigation, nitrogen, and cultivar factors on number of heads per plant, number of seeds per head, 1000-seed weight, grain yield, and biomass were significant. According to the results, cut-off of irrigation at the beginning of seed filling and middle of flowering stages leads to a reduction of 16.2 % and 68.1 % of seed yield compared to normal irrigation, respectively. Reducing the amount of nitrogen by 50 % compared to 100 % supply decreases seed yield 8.5 % and biomass by 12 %. The triple interaction of irrigation, fertilizer and cultivar was significant in stem diameter and head diameter. The interaction of irrigation and nitrogen levels showed that with decreasing irrigation levels, nitrogen uptake also decreased and reduced the number of seed per head. However, providing 100 % of the nitrogen requirement under drought stress conditions prevents a more severe decline in the number of grains per head.
esmaeil afshoon; Mohammad Reza Jahansooz; Hossein Moghadam; Mostafa Oveisi
Abstract
To study the effect of nitrogen fertilizer and irrigation regimes on some crop growth indices of forage maize under conventional and conservation tillage system, an experiment has been conducted in split plots with a randomized complete block design and three replications at University of Tehran’s ...
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To study the effect of nitrogen fertilizer and irrigation regimes on some crop growth indices of forage maize under conventional and conservation tillage system, an experiment has been conducted in split plots with a randomized complete block design and three replications at University of Tehran’s farm during 2018. Tillage systems, as the main plot in two factors, include conversation and conventional tillage, whereas water stress, being the subplot, is in three levels which are 30%, 60%, and 90% of moisture requirement. Also, nitrogen fertilizer, as the sub-sub plot, is at three levels, 0, 50%, and 100% of the recommended rate. Results in the flowering stage show that the highest leaf area index (6.28) and crop growth rate (34.01 gr m-2 day-1) have been obtained from the interaction between slight water stress (90% of crop water demand) and nitrogen (100% of crop demand) as well as the interaction between slightly water stress and 100% nitrogen in conventional tillage, respectively. The highest relative growth rate (0.08 gr gr-1 day-1) and total dry matter (1006.86 gr m-2) belong to simple impact of 100% nitrogen along with the interaction of slightly water stress and 100% nitrogen in conventional tillage, respectively. Results show that under severe water stress and higher application of nitrogen, the fertilizer will cause less crop dry matter under conventional tillage.
Mostafa Keshavarz Mehr; Hosein Moghaddam; Mostafa Oveisi; Javad Bazrafshan
Abstract
The present research has been conducted to parameterize and evaluate the APSIM-Wheat model for winter wheat and to use the model for evaluation of climate change effects on grain yield. The model is used to simulate leaf area index, dry matter, and grain yield of Roshan cultivar winter wheat in Karaj ...
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The present research has been conducted to parameterize and evaluate the APSIM-Wheat model for winter wheat and to use the model for evaluation of climate change effects on grain yield. The model is used to simulate leaf area index, dry matter, and grain yield of Roshan cultivar winter wheat in Karaj and Khomein regions between 2014 and 2015, under four irrigation regimes and three levels of nitrogen fertilizers. The experiments have been conducted in both regions as split-plot in a randomized complete block design. Irrigation is considered as main plot and nitrogen as a sub-plot. Model parameterization is based on observational data from full irrigation and 200 kg/ha nitrogen treatment in both regions. Results from the model evaluation show that the simulated values closely predict the observed values so that the RMSE in both regions is less than 670 and 450 kg/ha for biomass and yield, respectively, being below 0.56 for leaf area index as well. Normalized RMSE in all treatments has been below 17.8%, with Wilmot's index being above 0.82. The evaluation of model shows high performance and its possible use in other studies. Results from climate change analysis show that increasing the temperature from 0 to 5 °C leads to a maximum reduction of 75% in grain yield and an increase in carbon dioxide concentration, resulting in a maximum increase of 24% and, if the temperature increase exceeds three degrees Celsius, the grain yield will decrease in all possible concentrations of carbon dioxide.
Elias Soltani; Afshin Soltani; Mostafa Oveisi
Abstract
There are some computer programs to calculate germination related traits such as Germin which have using problems. The aim of this work was to adjust Germin for calculating germination related traits. Seed aging effects on the seedling emergence was modeled using the optimized Germin. This study was ...
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There are some computer programs to calculate germination related traits such as Germin which have using problems. The aim of this work was to adjust Germin for calculating germination related traits. Seed aging effects on the seedling emergence was modeled using the optimized Germin. This study was conducted based on completely randomized design in a factorial combination of five seeds aging treatments (0, 48, 72, 96 and 144h accelerated aging periods) and 3 levels of environmental factors. Results indicated that Chapman–Richards function adequately described cumulative emergence in all aging treatments and three environmental conditions. Emergence percentage and rate were decreased by seed aging periods from 145 to 194oC day. Results showed that observed thermal time for emergence increased as accelerated ageing periods increased and drought stress resulted in increased thermal time. For example, thermal time increased to 240oC day in 144h accelerated aged seeds in severe drought. Results indicated that with increasing thermal time in optimum condition, thermal time would increase linearly in the drought stress. Optimized program could calculate germination related traits. Therefore, it is recommended to use the optimized Germin in seed science research.
Sahar Seyedabbasi; Iraj Alahdadi; Mostafa Oveisi; Gholamali Akbari
Abstract
Field experiment was conducted to predict shoot emergence of Sorghum halepenseand Chenopodium albumL.in different planting dates of maize with stale seed bed or conventional planting. 3- parameterweibul gave a good description of cumulative shoot emergence percentage of S. halepense against ...
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Field experiment was conducted to predict shoot emergence of Sorghum halepenseand Chenopodium albumL.in different planting dates of maize with stale seed bed or conventional planting. 3- parameterweibul gave a good description of cumulative shoot emergence percentage of S. halepense against GDD. Planting dates were different in emergence rates. With delaying in palnting time, the rate of emergence and the maximum cumulative emergence decreased.Irrigating the field before planting increased weed seedling emergence. There was no difference between sowing dates in the maximum seedling emergenc, except for the last sowing date i.e. T5 that indicated a lower emergence rate.The last sowing date indicated the least emergence percentage. The current study showed that applying stale seed bed method provided an opportunity for the control of S. halepenseand ,Chenopodium album L.however,with delay in palnting time there was a less S. halepense and –Chenopodium album L.infested seed bed. The knowledge of the relationship between seedling emergence time and the prevailing environmental conditions could be useful to maximise the efficacy of weed control.