rapeseed

The application of various inputs, such as pesticides and chemical fertilizers, has been one of the most significant factors negatively impacting the sustainability of agricultural systems. To accurately assess the value of agricultural ecosystem services, both the positive and negative aspects of agricultural systems must be taken into account. In the past three decades, the emergy analysis has been developed for assessing environmental policies and resource quality based on the dynamics of complex environmental and economic systems. Emergy analysis can be used to evaluate the sustainability of agriculture. By definition, emergy is the amount of direct or indirect solar energy required to produce a good or service. By converting all forms of energy, resources, and services into a single unit, the solar emjoule (sej), emergy analysis can assess the interdependence of economic, social, and environmental factors. The production of three important oil crops of Sistan, including rapeseed, safflower, and sesame, was investigated using emergy and economic analysis techniques to evaluate the ecological health and productivity of the use of inputs in the production of oil crops in Sistan.

This research was conducted at the level of Sistan's oil plant production systems in the Northern provinces of Sistan and Baluchistan. This research used questionnaires and face-to-face interviews with the owners of small ownership systems to determine the input consumption and performance of these systems. According to their service life, the annual input energy flow in the form of structural facilities, buildings, machinery, and materials used in the systems was calculated. The RUSLE model was used to assess water erosion. Inputs are divided into four categories to analyze production systems: renewable environmental resources (R), non-renewable environmental resources (N), purchased renewable resources (FR), and purchased non-renewable resources (FN). After calculating all input and output flows, the raw data for each of the production systems was multiplied by their unit emergy value in Joules, grams, or Rials, according to Iran's conditions. This study utilized transformity, the renewable emergy ratio (R%), the rmergy yield ratio (EYR), the rmergy investment ratio (EIR), the rnvironmental loading ratio (ELR), the emergy sustainability index (ESI), the emergy exchange ratio (EER), and the emergy index of product safety (EIPS).

The total supporting emergy for rapeseed, safflower, and sesame production systems was calculated to be 7.28E+16, 4.75E+16, and 3.55E+16 sej.ha-1.yr-1, respectively. In all three studied production systems, wind emergy was the largest source of free environmental input. In all three studied systems, environmental non-renewable inputs accounted for the largest portion of total emergy input, which was 83.42 percent for rapeseed, 80.11 percent for safflower, and 84.4 percent for sesame. The high proportion of nonrenewable inputs in this study for all three production systems demonstrated the vulnerability of Sistan's landscape cultivation systems as a result of the obvious lack of water, severe soil erosion, and contamination of agricultural lands. The total amount of purchased inputs for rapeseed, safflower, and sesame production systems was estimated to be 1.14E+16, 8.78E+15, and 5.40E+15 sej.ha-1.yr-1, respectively. Nitrogen and phosphorus chemical fertilizers comprised the largest proportion of purchased inputs in all three systems.The transformity for rapeseed, safflower, and sesame production systems, respectively, was 3.88E+06, 3.76E+06, and 2.48E+06 sej.J-1. The higher transformability of the rapeseed production system was due to the lower input utilization efficiency of this system compared to the safflower and sesame systems. The values of the saffron system's environmental sustainability indices (ESI and ESI*), renewable energy ratio (%R), environmental loading ratios (ELR and ELR*), and modified investment ratio (EIR*) indicate that this system is more sustainable. The lower health of rapeseed and sesame systems based on emergy indices was primarily due to the large proportion of input emergy related to organic matter losses and soil erosion, which are nonrenewable environmental resources. The economic analysis revealed that the sesame production system generated a higher profit-to-cost ratio and net profit than the safflower and rapeseed systems.

This study demonstrated that emphasizing practical solutions in the comprehensive management of production ecosystems, particularly through the protection of soil organic matter and the prevention of erosion, can significantly enhance their ecological health.

In this research, the effects of combined application of biochar and nitrogen (N) fertilizer on some agronomical traits of rapeseed (Brassica napus L.), under water deficit stress conditions were studied in pot culture with a calcareous sandy loam soil.

Methods & Maerials: 

A factorial experiment was done in a completely randomized design with three replicates. The factors were organic matter at five levels (0, 0.75, and 1.5 g 100 g-1 from two sources  of biochar and wheat straw), N at two levels (150 and 300 mg kg-1 as urea), and moisture at two levels (without stress or optimum, 85–100 percent of field capacity, and stress, 50-60 percent of field capacity). Before the plants harvesting, leaf chlorophyll index, leaf water potential, stomatal conductance, and leaf area were measured. After the plant harvesting, water use efficiency, and some agronomical triats were determined.

Application of nitrogen and biochar significantly increased leaf chlorophyll index, leaf water potential, stomatal conductance, shoot dry matter weight, grain dry matter weight,  weight of one thousand seeds, water use efficiency and seed oil content. Wheat straw application decreased leaf chlorophyll index, number of leaves, relative water content, leaf water potential and leaf water use efficiency, but at the same time increased plant height, , stem diameter, stomatal conductance, shoot dry matter weight, , dry weight of seed, and thousand seed weight compared to the treatment without organic matter. Water defecit stress decreased the plant height, leaf number, stem diameter, stomatal conductance, relative water content, leaf water potential, pod number, fresh and dry weights of shoot, fresh and dry weights of root, fresh and dry weights of seed and weight of one thousand seed, except for water use efficiency and leaf chlorophyll index.

In this greenhouse study, B1.5 N150 FC0.5 treatment reduced nitrogen use compared to the same treatment with 300 mg N.kg-1 soil (B1.5 N300 FC0.5) without significant yield loss. The application of organic matter including wheat straw and biochar at both levels of 0.75% and 1.5% caused a significant increase in most of the agronomical traits of rapeseed plants, especially the seed oil content in a calcareous soil, and of course, future research in the field is recommended.

Phosphorus (P) is a macronutrient that its deficiency severely limits plant growth and production. Because of the complexity of P chemistry in soil, less than 30% of applied P fertilizer is absorbed by plants and the rest in the soil converts to unavailable forms. Organic matter can be applied to the soil to reduce soil P fixation and increase soil P bioavailability because organic matter and its decomposition products (e.g., organic acids) occupy the surfaces of phosphate adsorbents in soils and prevent the precipitation of phosphate compounds. During pyrolysis of organic material a complex mixture of P species is formed, which may include amorphous, semi-crystalline, and crystalline constituents, along with organic constituents. However, organic P forms will tend to disappear while inorganic P forms will subsequently be formed and crystallinity will increase with increasing pyrolysis temperature. The crystalline P minerals that have been identified in biochars include whitlockite [(Ca, Mg)3(PO4)2] pyrolysed from manure at 500 °C, dehydrated struvite (NH4MgPO4) produced from cattle manure and sewage sludge, and hydroxyapatite [Ca10(PO4)6(OH)2] made from slaughterhouse waste and from mixtures of that waste with either corn residue or wood. The crystallinity of hydroxyapatite was lower when corn residues or wood were added to the slaughterhouse waste and as result increased the soluble P fraction. To the best of the authors’ knowledge, the evidence to support the impact of biochar on P sorption and desorption in Iranian soils is scarce while taking account of the fact that P deficiency is dominant in approximately 72% of the arable soils. So, in this research, the effects of combined application of biochar pyrolysed at 300 ˚C and P fertilizer on dry matter and uptake of calcium (Ca), magnesium (Mg), iron (Fe), zinc (Zn), copper (Cu), and manganese (Mn) by rapeseed (Brassica napus L.), Hyola 308 cultivar, were studied in an alkaline loamy soil under greenhouse conditions.

After being washed with deionized water, wheat straw samples were milled, sieved < 1 mm, and then were oven-dried at 60 ºC for 24 h. The biochars were produced by slow pyrolysis of wheat straw at 300 ºC for 1 h under argon (Ar) gas flow at the heating rate of 10 ºC per minute. The produced biochars were transported in plastic containers for later analysis. Afterward, a factorial experiment was done on the basis of a completely randomized design with three replications. The factors were organic matter at 5 levels (no organic matter application, wheat straw 2%, wheat straw 4%, biochar 2%, and biochar 4%) and phosphorous (P) fertilizer at 3 levels (0, 20, and 40 mg/kg) as triple superphosphate. After the plant harvesting, shoot dry matter and the concentration and content of Ca, Mg, Fe, Zn, Cu, and Mn in plant shoot were determined by Atomic Absorption Spectrophotometer.

Wheat straw application significantly reduced rapeseed shoot dry matter compared to the control. At each level of wheat straw (2 and 4%), P application significantly increased shoot dry matter as compared to the control treatment. Under wheat straw application conditions, the using both levels of P (20 and 40 mg/kg) significantly increased shoot dry matter. This finding indicates the possible immobilization of P due to wheat straw application and the positive effect of P fertilizer under these conditions. Using biochar at both levels of 2 and 4 percent increased the rapeseed shoot dry matter by 46 and 56.5 percent, respectively, compared to the control. The combined application of straw and P reduced the Ca, Mg, Fe, and Cu uptake at both levels of biochar (2 and 4 %) compared to the control. However, the content of Zn and Mn increased at the biochar level of 2% compared to the control, but significantly decreased at the biochar level of 4% compared to the control.

According to the results obtained from this research, the use of biochar produced from wheat straw at the temperature of 300˚C increased the uptake of Fe, Zn, and Mn, which led to the improvement of the growth characteristics of rapeseed. In this research, the effect of biochar on the Cu concentration and content in shoot unlike other nutrients was negative. According to the results, the wheat straw drived biochar at 300 °C improved rapeseed plant growth characteristics and nutrients uptake except Cu. Also, application of biochar and P at 2% and 20 mg/kg levels, respectively, is recommended to reduce the consumptions of P fertilizer without yield reduction of rapeseed in under similar conditions. In addition, application of wheat straw at 2 and 4 % levels is not recommended and future research should be done at its lower levels. Finally, it was concluded that biochar may play an important role in soil fertility and plant production, so further research should continue.

Rapeseed is one of the major oilseed crops in the world. Increasing the seed yield and oil content of rapeseed is important for the production of rapeseed oil. The maximum seed yield is achieved in the optimal plant density. By reducing the plant density, it is partially compensated by the increase in number of secondary branches, biomass, while in high density, rapeseed plants are often prone to increase the incidence of disease (Rondanini et al., 2017). Determining the optimal density in crops depends on many factors such as plant type, soil fertility, available water and environmental conditions (Hiltbrunner et al., 2007). Rapeseed genotypes differ from each other in terms of the number of seeds per silique, the number of siliques per unit area, seed weight, and the number of secondary branches. The objective of the present experiment is to obtain this information and determine the appropriate plant density to obtain the highest seed yield and to identify the role of yield components in production and the relationships between them in new rapeseed cultivars.

The seedinging rate was determined based on the thousand seed weight of rapeseed cultivars using a fine seed machine and 1 kg., 2 kg, 4 kg and 8 kg.ha-1 seed were used. The rapeseed cultivars used were Architect, Rohan and Okapi. Factorial arrangement in randomized complete blocks design with three replications was used. The experiment was carried out in research farm of Fadak Agro-industry Company in Markazi province, Iran in 2021-22 and 2022-23 growing seasons. Phenological traits including days to flowering days to maturity, seed filling duration, seed filling fraction (the ratio of seed filling duration to the total growth duration from seeding to maturity) and plant height were measured and claculted. Seed yield and its component, including; number of secondary branches, thousand seed weight, number of silique.plant-1, number of seed.silique-1, were measured on randomly harvested 20 plants from each experimental plot and calculating the average. Seed yield was obtained with harvesting from 50 m2 in each plot. Seed oil content was measured using an NMR spectrometer (ISO 10565, 1998). Analysis of variance was performed using SAS 9.1 software, and relationship between traits was studied using Excell 2003 software. LSD test, at the 5% probability level, was used for means comparison.

Results showed that days to flowering varied from 198.7 to 205.8 days and had a decreasing trend with the increasing of seeding rate. The longest seed filling duration (30.5 days) was recorded for cv. Architect. The shortes seed filling duration (24.3 days) belonged to cv. Okapi at the seeding rate of 2 kg.ha-1. The 1000 seed weight of the cv. Architect, cv. Rohan and cv. Okapi were 5.22 g, 4.36 g and 3.39 g, respectively. With the increase of seeding rate, 1000 seed weight decreased from 4.56 g in 1 kg.ha-1 to 4.1 g in 8 kg.ha-1 seeding rates. The highest number of secondary branches in the cv. Architect was obtained at 1 and 2 kg.ha-1 seeding rates. The highest seed yield in cv. Architect (4731 kg.ha-1) was obtained in seeding rate of 4 kg.ha-1. The plant height decreased from 172 to 152.6 cm. with increasing seeding rate.The number of seed.silique-1 had a downward trend. With the increase in seeding rate, the seed oil content showed a significant upward trend. Seed yield significantly correlated with 1000 seed weight, number of secondary branches, plant height and seed oil content.

With the increase in seeding rate, seed oil content increased and this result can be related to the increase in the number of main stems with the increase seeding rate. Seed filling fraction (the ratio of seed filling duration to the total growth duration from seeding to maturity) and its positive and significant correlation with yield traits such as seed yield, 1000 seed weight and seed oil content showed that the long seed filling duration in addition to the early flowering is a desirable attributes. According to the results of this experiment, the optimum seeding rates for cv. Architect, cv. Rohan and cv. Okapi were 2, 4 and 8 kg.ha-1, respectively. In new rapeseed cultivars, cv. Architect and cv. Rohan, early flowering, longer seed filling duration and higher seed filling fraction may have important roles in achieving higher seed yield.

Salinity is one of the major abiotic stresses and the most limiting factor in agricultural production worldwide, affecting the growth, development, and final yields of crops. Rapeseed is one of the most important sources of oilseeds in the world, and its seeds contain more than 40% of oil. Moreover, the meal obtained from oil extraction has more than 35% protein, hence it currently ranks third among oil crops in the world after soybean and oil palm, making it necessary to identify the genotypes that tolerate salinity stress. The development and improvement of rapeseed cultivars with salinity tolerance and acclimation offer promising prospects for improving sustainable production in this area. Therefore, the current study aimed to investigate the responses of rapeseed genotypes to salinity stress through analyses of agronomic and biochemical traits.

The genetic diversity between rapeseed lines in terms of agronomic, morphological, and physiological traits in saline soils was investigated in an experiment based on a randomized complete block design with 17 autumn rapeseed genotypes with three replicates in the research farm of East-Azarbaijan Agricultural and Natural Resources Research and Education Center. The measured traits were plant height, the number of fertile pods, number of seeds per pod, pod length, pod area, plant growth rate, 1000-seed weight (TSW), seed yield, oil content, and oil yield. The relationships between yield, yield components, and morphological traits were explored using the analysis of variance (ANOVA), comparison of averages, correlation analysis, cluster analysis, and biplot to understand the relative importance of traits affecting the yield of the studied genotypes.

The studied genotypes were significantly different from each other in pod length, pod area, number of fertile pods, number of seeds per pod, plant growth rate, seed oil percentage, plant height, TSW, grain yield, and oil yield. However, there were no significant differences between the studied genotypes in terms of harvest index and number of actual pods to potential pods. According to the mean comparisons, genotypes 5, 11, and 15 can be introduced as salinity-tolerant lines, and genotypes 2, 4, 6, 9, and 12 can be considered salinity-sensitive lines. According to the other traits, genotype 11 produced a high pod length, number of fertile pods, oil percentage, and oil yield, genotype 5 had a high growth rate and oil percentage, and genotype 15 presented a high height and number of fertile pods. According to the cluster analysis, the second and third groups contained tolerant and susceptible genotypes, respectively. The genotypes in the second group had the highest percentage of positive deviation from the overall mean for grain yield, plant height, harvest index, seed oil percentage, pod length, pod area, and number of fertile pods. Based on the biplot analysis, Karaj 8 and 14 genotypes had a strong relationship with the number of  fertile pods, number of seeds per pod, pod length, pod area, and plant growth rate. Based on the obtained results, the plant height, TSW, seed yield, and oil content traits were closely correlated with Karaj 5, 7, 11, 10, and 15 genotypes. Based on the results of correlation analysis, the correlation coefficient of seed yield was positive and significant for three traits, i.e., plant height, oil percentage, and number of fertile pods, and the highest correlation coefficient (r = 0.879) was obtained for seed yield with seed oil percentage. Positive and significant correlations were measured for the number of seeds in pods with pod length (r = 0.699), pod area (r = 0.555), number of fertile pods (r = 0.678), and number of actual pods. Therefore, genotypes characterized by longer and more abundant pods play a crucial role in improving seed quantity, a key component of grain yield in saline environments. Consequently, the size and number of pods per plant serve as indicators of high-yield potential under such conditions. Based on the results of the principal component analysis (PCA), the first and second components had the highest relative variances, accounting for 44.66% and 31.22% of the total variance, respectively. Together, these two components accounted for 75.88% of the total variance. Factor loadings showed that traits such as number of fertile pods, seed yield, oil yield, and seed oil content had the highest factor loadings in the first component. Similarly, the plant growth rate had the highest factor load in the second component among all the studied traits. Cluster analysis divided the genotypes into four groups, and its dendrogram showed that all the studied genotypes were divided into four separate groups based on all the measured traits. The first group comprised three Karaj 1, 13, and 16 genotypes, the fourth group (like the first group) contained three Karaj 5, 11, and 15 genotypes, and the third group had five genotypes, namely Karaj 3, 7, 8, 10, and 14. The remaining genotypes were assigned to the second group.

The results of the present study demonstrate acceptable genetic diversity among rapeseed genotypes in terms of the evaluated traits in saline lands. This shows the importance and the possibility of using these genetic resources to achieve promising and superior genotypes in breeding programs.

Biofertilizers play major role in sustainable agriculture. Biofertilizers are inoculants containing useful microorganisms which are used in solid, liquid and/or encapsulated formulations. Different materials can be used as liquid carriers. Increasing inoculant longevity by using different materials is the main purpose in production of liquid inocula. These additives are carbon-based and reduce environmental stresses. In this study the effectiveness of liquid inocula of Enterobacter cloacae S16-3 on oil content, fatty acids and nutrient uptake of rapeseed in a sterile sandy loam soil were evaluated. Nine liquid inocula of S16-3 (F1-F9) were prepared using different amounts of materials including glycerol, polyethylene glycol (PEG), trehalose, carboxymethylcellulose (CMC), Arabic gum (AG), polyvinylpyrrolidone (PVP), glucose and starch, in different combinations. Then, the effect of liquid inocula on growth of rapeseed (Brassica napus L.) cultivar hyola 308 was investigated.

The experiment was carried out in greenhouse condition based on completely randomized design (CRD) with three replications. The factors were including 9 liquid inocula (F1-F9), in all these treatments, 70% of NPK was added to the soil in each pot, since we assumed that S16-3 is able to supply only 30% of these elements, one control treatment without adding any bacteria and fertilizer (negative control), and two positive controls (using NPK equal to 70% and 100% of fertilizer recommendation). Germinated seedlings of rapeseed were planted and inoculated with inocula in each pot. Except for NPK elements, other micronutrients were provided based on soil test; however, in the case of nitrogen, phosphorus and potassium elements that were the main objective of this experiment, no chemical fertilizer and bacteria were used in negative control treatment. In positive control (100NPK), based on the soil test and previous experiments, 100% of the recommended amount of fertilizer, equivalent (56.5 mg N/kg soil, from Urea source), (13 mg P/kg soil, from triple superphosphate source) and (31.3 mg K/kg soil, from potassium sulfate source) were used, moreover, for other positive control treatment (70NPK), 70% of the above values in pot culture were added to the pots. During the growth period, irrigation was performed with sterile water and the moisture content of the pots was maintained by weighing in a moisture range (0.7 - 0.8 FC). In pot culture, characteristics such as dry weight of roots, shoots and seed, seed oil percentage and fatty acids, uptake of nitrogen, phosphorus, potassium, iron, zinc, manganese and calcium in the root and shoot were measured.

The results obtained from the greenhouse experiments showed that the dry weight of roots, shoots and seed, seed oil percentage and fatty acids, uptake of nitrogen, phosphorus, potassium, iron, zinc, manganese and calcium in the root and shoot of rapeseed (Brassica napus L.) cultivar hyola 308 were significantly influenced by the presence of E. cloacae bacteria (in the form of nine inocula) and 100NPK and 70NPK treatments. The highest percentage of seed oil (47.02%) and the highest amount of oleic acid (53.1%) was obtained by F9 (glycerol, glucose, AG, PEG) treatment, and oil quality was affected by bacterial inoculation. the highest amount of saturated fatty acids, such as stearic acid (4.5%) and palmitic acid (5.6%) was measured in without inoculation treatment (negative control). Nutrition analysis in dry tissue of plant showed that 100NPK treatment had the highest N, K, Fe, Zn and Ca uptake in the plant, and among liquid inocula treatments (F1-F9), the highest uptake of these elements belonged to the F5 (AG, starch, PEG). The highest amount of total P in F1 treatment (glycerol, trehalose, CMC) and F4 (trehalose, AG, PEG) and highest Mn absorbed in the plant were obtained in F5 treatment.

In most measured indices, the effects of liquid inocula had higher performance than without inoculation treatment (negative control). From the nutritional point of view, F5 (AG, starch, PEG) liquid inoculant were better than the other inocula. F9 treatment had a significant effect on quantitative and qualitative characteristics of rapeseed oil.

Water, food, and energy are three essential sources for maintaining life and fostering socio-economic development, and they are inseparably interconnected. The aim of the present study was to examine the indicators of water and energy efficiency of major agricultural products, namely, wheat and rapeseed, in two different climates in Sari (temperate and humid) and Sharifabad (hot and semi-arid) plains in Iran. To investigate these indicators in wheat and rapeseed crops, data from the agricultural year 2021-22 were utilized. Initially, the number of samples was determined based on the Cochran formula. Then, sampling was done using a questionnaire designed by the authors. The questionnaires numbered 300, and the collected information included inputs and production quantities. The results showed that the average water physical efficiencies in Sari Plain for wheat and rapeseed crops were 1.13 and 0.67 kg/m3, while in Sharifabad Plain, it was 0.83 and 0.35 kg/m3, respectively. Furthermore, the results indicated that the highest level of input energy in Sari and Sharifabad plains for wheat was 80618 and 71072 MJ/ha, respectively. The results also showed that greenhouse gas emissions were higher in Sari than in Sharifabad, probably because of excessive use of fertilizer and pesticide in Sari. The highest greenhouse gas emissions in Sari for wheat were 2495 kg CO2/ha, and in Sharifabad, it was 2299 kg CO2/ha. Overall, the results indicated that crop performance in humid regions was higher than in dry and semi-dry regions, and this indicator depends on various parameters, including water consumption and agronomic management.

To evaluate the response of different rapeseed cultivars to cut-off irrigation at the end of season on seed fatty acids, glycosinolates and agronomic characteristics of cultivars, a split plot experiment based on randomized complete block design with three replications in Moghan Research Center ,was conducted during 2014-2016 cropping season.Experimental treatments were levels of irrigation as the main factor in three levels, normal irrigation (control) according to plant needs and local customs, low irrigation stress in the form of irrigation cutting at the plowing stage and irrigation cutting at the flowering stage and Rapeseed cultivars as sub-factors in 11 levels included 003RGS, Sarigol, Zafar, Dalgan, Julius, Jacomo, Jerry, Jerom, Zabollo, 401Hyola, 4815 Hyola. In this study, the yield and yield components of rapeseed were not significantly affected by water stress after flowering and pods and only post-flowering stress reduced the number of seeds per pod by 4.7%. Biomass also decreased to 2.9% under the influence of stress. Despite the above results, the properties of rapeseed oil were strongly affected by water deficite. The amount of palmitic acid due to stress decreased to 32.6% (at Jerome cultivar), while the amount of linoleic and, erosic acids and glucosinolates under stress increased to 84.4%and 148.7% (at Zafar cultivar) and 118.7% (at Jerome cultivar). In this study, the highest grain yield  sa2986 and 2981 kg / ha was obtained in Julius and RGS003 cultivars. In these cultivars, all three components of yield as , yield of number of pods per plant, number of seeds per pod and 1000-seed weight were higher than with comparison of other cultivars.There was a high difference between cultivars for palmitic, lithinolenic, linoleic, oleic acids and glucosinolate. In general, Zafar and , Julius cultivars were the best cultivars due to their high  yield and oleic and linoleic acids content.

Rapeseed with the scientific name (Brassica napus L.) are one of the most important oilseed crops in the world. Considering the country's increasing need to import oil and the importance of rapeseed among oilseeds plants, increasing the yield and percentage of oil is very important. Therefore, identification the traits that increase seed yield, play an important role in the success of breeding programs. Yield is a complex trait that is affected by many factors. direct selection of a variety for yield is not often very effective, so investigating the relationships between grain yield and other traits for indirect selection may be effective. In such a situation, correlations may not clarify the relationships well, therefore, multivariate statistical methods and path analysis can help in understanding the nature of the relationship between traits for direct or indirect selection and improve the efficiency of selection in breeding programs plants become useful.

In this study, eight genotypes of spring rapeseed (SPN-202, SPN-204, SPN-206, SPN-207, SPN-217, SPN-225, SPN-227, SPN-182) along with 56 rapeseed hybrids (F1) were planted in a randomized complete block design with three replications in 2019-2020 crop years in the research farm of Gorgan Agricultural Research Station. During the experiment, phenological, morphological traits, yield and yield components were recorded. The normality of the data was evaluated based on the Kolmogorov-Smirnov method. In order to understand the relationships between traits and to identify the traits affecting on grain yield, at first, correlation coefficients were estimated, then stepwise regression were done. Then, path analysis based on correlation coefficients was used to determine the direct and indirect effects of traits. Finally, all traits were grouped based on principal component analysis.

The results of analysis of variance indicate a significant difference for all studied traits at the probability level of one percent. The coefficient of variation (C.V) for the traits varied from 1.37 (physiological maturity) to 10.31 (number of sub-branches), which indicates that there is sufficient accuracy in conducting the research. The results of correlation evaluation showed that number of pod per lateral branches (0.864), number pods per Plant (0.865), number of lateral branches (0.466), physiological maturing (0.329) and number of grain per pod (0.358) had a positive and significant correlation with grain yield (P<0.01). Stepwise regression analysis showed that the traits of number of pods per plant, number of grain per pod and 1000-grain weight has a decisive role on grain yield. Based on the results of path analysis, number of pods per plant had the most direct effect (0.881) and number of grain per pod had the most indirect effect (0.053) through the number of pods per plant on grain yield. In order the results of principal component analysis, four components were able to explain 75.91% of the changes in the measured data of 64 rapeseed varieties.

Results of the path analysis showed that number of pods per plant, number of grain per pod and 1000-grain weight had a direct positive effect on grain yield. Also, the stepwise regression analysis showed that the stated traits have the highest regression coefficients. Therefore, selection for these traits can be very effective in achieving high performance

In order to investigate the effect of silica and calcium content and harvest dates on yield and yield components of rapeseed as a factorial split in a randomized complete block design with three replications in experimental farms in Aftab region of Tehran province in two cropping years 2018-2019 and 2019-2020 were implemented. Experimental factors include harvest date in three levels one week after the start of yellowing of pods, two weeks after the beginning of yellowing of pods and time of complete yellowing of pods, silica in three levels of zero (control), 3 and 6% of the source was sodium and calcium silicate at three levels of 2, 4 and 6% of the source of calcium sulfate. The results showed that the effect of year on plant height, number of pods per plant, number of seeds per pod and anthocyanin was significant and the second year had the highest amount of these traits. It was observed that the best grain yield of 2477.02 kg / ha and harvest index of 24.83% was related to harvest one week after the start of yellowing of pods and with delay in harvest, 1000-seed weight, grain yield, Biological yield and harvest index decreased and anthocyanins increased. According to the results, silica foliar application with 32.81% increase in plant height, 11.8% number of pods per plant, 31.48% number of seeds per pod, 17.2% weight per thousand seeds, 24.31% grain yield, Biological yield and harvest index and reduction of anthocyanin and electrolyte leakage were associated. The most positive effect on physiological characteristics and yield and yield components was obtained in 6% silica spray. With increasing calcium concentration, plant height, number of pods per plant, number of seeds per pod, 1000-seed weight, grain yield, biological yield and harvest index decreased and anthocyanin and electrolyte leakage decreased, the maximum positive effect on these traits in foliar application 6% calcium was observed. The results showed that silica and calcium had an additive effect on yield and yield components and the best grain yield was obtained by consuming 6% silica with 6% calcium and harvesting one week after the start of yellowing of pods.