Iranian Journal of Field Crops Research
Year:2017 | Volume:15 | Issue:2|Papers Count:21

Introduction: In order to improve the efficiency of weed management and reducing herbicide application, determining the most sensitive weed-crop competition period is very important. There is a special period in plant life cycle, that if the crop is kept free of weeds, yield reduction has not significant economically and also weed control after that will not affect crop yield improvement. This period is known as the critical period competition affected by climate, weed species dominance, field management methods and crop type and their cultivars. Sesame is one of the important crops due to its high oil quality. This low input crop is very considerable in terms of economic in arid and semi-arid subsistence farming area. Despite the importance and antiquity of sesame cultivation in Iran, there is low information about the effects of weed on its growth and yield and also critical period of weed competition. So, the present study was carried out to determine the critical period of weed in two Common genotypes of sesame (Oltan cultivar and kalat Landrace) in Khorasan Razavi province.Material and Methods: This study was conducted at Research Farm of College of Agriculture, Ferdowsi University of Mashhad with 36o 15’ N latitude and 59o 28’ E longitude and 985 m above the sea level, during 2009 growing season, Mashhad, Iran. The experiment was carried out as split plot based on the randomized complete block design with three replications. Treatments were sesame genotypes (Olten cultivar and Kalat landrace) as main plot and weed-free periods (20, 30, 40, 55 and 70 days after emergence (DAE)) and weed interference -periods (20, 30, 40, 55 and 70 DAE) with two full season weed control and full season weed competition, were considered as sub plots. Sampling from weeds was conducted before weeding and before the end of sesame growing season in interference and weed free treatments, respectively. Sesame plants harvested at physiological maturity stage, after eliminating the border effect area, from six m-2 and after drying in natural condition, sesame seed yield was reordered. To determine the critical period of weed, non-linear regression was used by fitting the data to Logistic and Compertz models. MSTAT-C software also was applied for analysis of variance and means comparison.Results and Discussion: Results showed that, the highest weed density was recorded in weed interference conditions 30 days after sesame emergence and reduced after that. The dominant weeds werePortulaca oleraceae, Convolvolus arvensis, Amaranthus retroflexus, Chenopodium album and Echinochloa crus-galli.Weed dry weight was decreased on average by 85 percent in weed free treatments up to 44 days after emergence compared to full season weed interference control treatment. Sesame yield was decreased with increasing the weed interference periods, but it was increased with increasing weed free period treatments. Weed dry weight decreased significantly by increasing weeding duration. It was estimated that the critical period of weed control in Kalat landrace were 27-48 and 30-40 days after emergence with considering 5% and 10% acceptable yield losses, respectively, while in Oltan cultivar were 22-72 and 34-58 days after emergence, respectively. So the critical period of weed control in Kalat landrace was shorter than Oltan cultivar.It seems that in kalat genotype once weeding during its critical period of weed control is enough, while it is necessary at least twice in oltane cultivar. Short critical period of weed control in kalat landrace sesame may be due to its shorter growing season and its faster canopy closure than Oltan cultivar.

Introduction: Human diets strongly rely on wheat (Triticum aestivum L.). Its production has increased dramatically during the past 50 years, partly due to area extension and new varieties but mainly as a consequence of intensified land management and introduction of new technologies. For the future, a continuous strong increase in the demand for agricultural products is expected. It is highly unlikely that this increasing demand will be satisfied by area expansion because productive land is scarce and also increasingly demanded by nonagricultural uses. The role of agricultural intensification as key to increasing actual crop yields and food supply has been discussed in several studies. However, in many regions, increases in grain yields have been declining Inefficient management of agricultural land may cause deviations of actual from potential crop yields: the yield gap. At the global scale little information is available on the spatial distribution of agricultural yield gaps and the potential for agricultural intensification.Actual yield is mostly lower than potential yield due to inefficient management and technological that difference between these yields is considered as yield gap. Understanding of relative share of every management factors in yield gap could be as one of the important keys to reduce gap and close actual yield to potential yield.Materials and Methods: In order to evaluate the amount of wheat yield gap and also relative share of management and technological variables in yield gap, frontier production function was used which is a multivariable regression. The frontier production function to be estimated is a Cobb-Douglas function as proposed by Coelliet al. (2005). Cobb-Douglas functions are extensively used in agricultural production studies to explain returns to scale. We propose a methodology to explain the spatial variation of the potential for intensification and identifying the nature of the constraints for further intensification. We estimated a stochastic frontier production function to calculate global datasets of maximum attainable grain yields, yield gaps, and efficiencies of grain production at. Applying a stochastic frontier production function facilitates estimating the yield gap based on the actual grain yield data only, instead of using actual and potential grain yield data from different sources.Therefore, the method allows for a robust and consistent analysis of the yield gap. The factors determining the yield gap are quantified at both global and regional scales.For this purpose, climatic information and wheat yield of different provinces were obtained from Iran meteorological organization and Agriculture Jahade organization, respectively. Wheat potential yield in different provinces was simulated by WOFOST model. Wheat gap was gained by difference between actual and potential yield in different provinces. Relative share of climatic variables in potential yield and also relative share of management variables included irrigation, fertilizer application, mechanization, pesticide application and manure in wheat yield gap was calculated by frontier production function.Results and Discussion: The results showed that the effect of precipitation and radiation on wheat potential yield was positive and the impact of temperature was negative. Precipitation had the highest impact on wheat potential yield among other climatic variables. The range of wheat yield gap was from 1646 to 4470 kg ha-1 and 29 to 58% in Iran. Generally, the effect of all management variables on wheat yield gap was negative so that wheat yield gap was reduced by improving of these variables. Among studied management variables, irrigation had the highest effect on yield gap reduction, especially in dry-warm climate and fertilizer application was the second factor which had high effect on yield gap reduction. Therefore, to reduce wheat yield gap in Iran, irrigation management and fertilizer application should be considered.Conclusions: Between studied climate variables, the relative contribution of temperature and rainfall was higher on wheat yield potential compared with radiation in all provinces except the province of Zanjan, Golestan, Gilan and Mazandaran. The highest gap yield (4470 kg ha-1) was assigned to Ilam and Mazandaran provinces. Irrigation and fertilizer application were the more affective variables in yield gap induction.

Introduction: Wheat (Triticum aestivum L.) as the most strategic crop for human nutrition is cultivated in many countries under rainfed conditions in semiarid regions. To be vital importance to predict rainfed wheat yield and determine the important factors which affect this crop. Modeling is one of the approaches to predict the response of land to land use. Artificial neural networks (ANN) are considered as one of the modeling approaches to yield prediction and determination of the most important parameters in crop productions. In rainfed wheat hilly land of central Zagros of Iran, there are various parameters that influence this crop production. Therefore, the objective of this study was to identify these important factors.Materials and Methods: This study was conducted for two years and at two sites under rainfed conditions in Koohrang and Ardal districts in Chaharmahal and Bakhtiari provinces, central Zagros of Iran. At both sites, the study was made on farmer–operated winter wheat fields. At the Koohrang and Ardal sites, 102 and 100 sampling points were selected, respectively.202 sampling points were chosen on the landscape covering summit, shoulder, backslope, footslope, and toeslope at two sites with varying climatic conditions. Four parameter groups including terrain attributes, soil physical and chemical properties, precipitation, and weed biomass, including 54 factors were used as the inputs, and wheat grain and biomass yield as the targets for ANN models. A feed forward back-propagating ANN structure was used to develop yield prediction models. The data set was randomly shuffled; 60%, 20% and 20% of them were used for the learning network, testing and verification, respectively. After determination of the best structure of ANN model, crop yields were predicted by the ANN models. By the Hill sensitivity analysis method (Hill, 1998), response of each factor was studied and determined the most effective parameters on grain and biomass yield. This method calculates relative sensitivity coefficient by dividing the sensitivity coefficient of every variable when the variable is reduced 10% by the maximum sensitivity coefficient, therefore the maximum relative sensitivity coefficient is 1.Results and Discussion: The descriptive statistics for various soil characteristics showed that, soil chemical and physical parameters can be classified into three orders. Sand, TN, Kava., Pava., SOM, CCE, and gravel showed high variability (CV>35); clay, silt, and CEC had moderate variability (35<CV>15); and SP and pH indicated low variability (CV<15). The lowest variability was attributed for pH, and the highest is for Pava. Summary statistics of terrain attributes show that the lowest and the highest skewness ascribed to plan curvature and relative stream power, respectively. In this study, the effect of management practices was evaluated by weed biomass. The data on weed biomass percentage ranged from 2.69 to 105.88 Kg ha-1 and this high variability most likely related to farmers’ management practices. Coefficient of variation of grain yield and biomass yield were 49.71 and 42.97%, respectively. It seems that this variability describes to landscape position, various management practices at the two different study sites.The best structure of the ANN models was ascertained for each component yield. Each of the trained structures had 54 input nodes in 4 groups and one output node. The hidden-layer nodes were determined 90 and 50, and the optimum iteration learning rates based on trial and error 9000 and 10000 for grain and biomass yield, respectively. The ANN models for grain and biomass yield resulted in R values of 0.92 and 0.87, respectively, and explained 84% and 76% of the variability in grain and biomass yield, respectively.For grain yield, the sensitivity analysis results showed that, in general, all of the considered parameters were important, but weekly precipitation group was more important for grain yield than the other groups, and precipitation of the 30th, 29th, 10th, 12th, 25th and 13th weeks of the growing season were identified as the mostimportant weekly precipitations. The second important group was management group (weed wt), the third one was soil characteristics group (soil total nitrogen), and the forth one was terrain attributes (plan curvature and sediment transport capacity index). For biomass yield, all parameters were important, but the plan curvature was identified as the most important variable. After plan curvature, weekly precipitation during the 1st, 4th and 9th weeks, catchment area, 25th week, available potassium, profile curvature, 14th and 21th weeks precipitation were the ten top important parameters, respectively.

Introduction: The maize as the oldest cultivated plant, is ranked second and first in terms of cultivated area and amount of production, in the world respectively. Although, researchers have improved the yield of corn by introducing new lines and hybrids, new genotypes alone cannot increase agricultural production, and it is necessary that appropriate and advanced agricultural techniques also be used to maximize corn yield. Maize is one of the most important crops in Golestan province, which is planted in more than 5000 hectares of agricultural land. In Golestan Province, different tillage systems are used for planting maize. Conservation tillage is a new and widespread method in this province, which many farmers use this method every year for cultivating their crops. The main objective of this study was to investigate the effects of different tillage systems on growth indices and yield of maize.Materials and Methods: To study the effects of different tillage systems on qrowth indices and forage yield of corn, an experiment was conducted using a Nested design at Azadshahr city. Treatments included no-tillage, minimum-tillage and conventional tillage. Each treatment was carried out in a separate 30´50 m plot. Cultivar 770 was planted in all plots with row spacing of 75 cmand the distance between plants on the ridges was 14 cm.Sampling was done by a 1*1 m2 quadrate in six phenological stages of maize including two leaf-stage (9 days after planting), six-leaf stage (26 days after planting), flowering (55 days after planting), (71 days after planting), (85 days after planting) and 86 days after planting. At each stage, 15 quadrates were randomly sampled in each plot. Leaf area and dry weight, height of each plant and total fresh and dry weight of maize was measured at laboratory.Results and Discussion: Net assimilation rate decreased following a quadratic equation in all treatments.Although the amount of NAR was estimated 13.5, 13.16 and 13.11 g.m-2.day-1 for conventional, minimum and no tillage, respectively but there was not significance different between the tillage systems in this regard. The maximum amount of NAR occurred at 17.3, 17.4 and 17.5 days after planting for conventional, minimum and no tillage, respectively. The value of this index at the end of the growing season (86 days after planting) was estimated as 0.41, 0.45 and 0.47 g.m-2.day-1 for conventional, minimum and no tillage, respectively.Relative growth rate decreased following a quadratic trend for all tillage systems. In conventional tillage, RGR declined from 0.24 g.g-1.day-1 at the beginning of the growing season to 0.01 g.g-1.day-1 at the end of the growing season. There was no difference between estimated RGR of the tillage systems both at beginning and at the end of growing season.Maximum crop growth rate occurred at 54 days after planting in all three tillage systems. The maximum value of CGR was estimated 41, 41 and 40 g.m-2.day-1 for maize in conventional, minimum and no tillage systems, respectively. CGR was estimated as 3 g.m-2.day-1 at the beginning of the growing season for all treatments; this index was estimated 15, 15 and 14 g.m-2.day-1 at the end of the growing season, for conventional, minimum and no tillage systems, respectively.Result showed that although tillage systems did not effect on dry weight of maize, forage yield of maize in conventional system (71 ton.ha-1) was significantly more than minimum (67 ton.ha-1) and no tillage (64 ton.ha-1) systems.

Introduction: Crop models are the most important parts of ecological models. These models could provide the possibility of crop systems prediction in addition to increase the understanding of their performance.Allometric relationships of plants show the changes of growth of one part in comparison to the other parts of the plant. Determining the appropriate plant density in crops, especially wheat has the high importance which affects some characteristics such as yield and yield components. This effect varies between different stages of plant growth.Materials and Methods: This research has been done in research station of Gorgan University of Agricultural Sciences and Natural Resources (37o 45’ N, 54o 30’ E and 120m asl) in the growing season of 2012-13. The experiment was conducted in a factorial experiment with randomized complete block design with four replications as base. Treatments consisted of two wheat cultivars (Koohdasht and Morvarid) and 7 plant densities (50, 100, 200, 350, 500, 650, 800 seed.m2). Each replication consisted of 14 plots and each plot had 10 rows with length of 5 m, width of 2m and a row spacing of 20 cm. Plot distances from each other was 40 cm and block distances was 1 m to each other. Measurements were done from tillering to the end of the growing every 7 to 10 days (depending on weather conditions). Cumulative thermal units were calculated using GDD_Calc program.Power model and non-liner segmented regression model were used to describe allometric relationships.Results and Discussion: In fitting allometric equations related to plant height, results showed that plant height in wheat starts from emergence and reaches the maximum in the anthesis stage and then remains constant.Hence, fitting equations were done to find allometric relations of wheat plant height and coefficient of 0.94 and root mean square error between 6.80 and 5.16 showed that the equation could well describe the height of plant during the growing season. Checking coefficients showed that there was no significant differences between a coefficient but significant differences was investigated in b coefficient and X0 coefficient. The analysis of the relationship between plant height and the number of leaves in main stem showed a significant effect according to b coefficient with coefficient of determination of 0.92, in different densities. Coefficient of determination values greater than 0.97 indicated a strong relationship between plant height and shoot dry weight, but the analysis showed no significant effect in terms of a (plant height when shoot dry weight is 1 gr) and b coefficients. In addition, regarding the relationship between the height and total dry weight of vegetative parts in different plant density, coefficient of determination values greater than 0.97 and ranges of root mean square error between 4.86 and 9.119, belong to the plant densities of 50 and 800, respectively, which showed a very good correlation between the height and the total dry weight of vegetative parts. The a coefficient (plant height when total dry weight is 1 gr) had significant difference and decrees about 0.0036 unit according to each plant more dense but for b coefficient, there was no significant difference.Conclusions: In general, the results revealed that plant height has significant correlation with the number of leaves in main stem, shoot dry weight and total dry weight of vegetative parts by coefficient of determination 0.93, 0.97 and 0.96, respectively. In addition, the correlation coefficient for producing leaves in main stem was 0.93.

Introduction: In order to evaluate the effects of salt stress on membrane stability, chlorophyll a and b, carotenoids, yield components and grain yield of seven maize hybrids (Ksc700, Ksc500, KSc704, Ksc301, Ksc647) (Iranian hybrids) and Ksc404 and maxima (foreign hybrids), a test was conducted in research field of faculty of agriculture in Shahid Bahonar University of Kerman, Iran in 2011 using plot splits in the form of complete random block with three replications. The main plots included four salinity water of irrigation water with electrical conductivity of four, six, eight and 10 dS/m, respectively, and subplots, including the mentioned hybrids. According to the results, increase of salinity level led to decrease of all evaluated traits, with exception of carotenoids, in a way that the highest level of measured traits were obtained from the lowest salinity level.Calculation of correlation coefficients between the traits demonstrated a positive and significant correlation between grain yield and membrane stability in 120 minutes (r=0.61**) and grain yield and the 1000-grain weight (r=0.93**). In this research, the minimum and maximum amount of grain yield were estimated as 10610 and 5750 kg/ha, respectively, in salinity level of 4 and 10 Ds/m. Moreover, among the hybrids, the Ksc704 hybrid had the highest level of membrane stability and grain yield in the evaluation condition, and was introduced as the salt tolerant hybrid for culture in such conditions....

Introduction: Intercropping is one of the components of sustainable agriculture and as part of crop rotation in the design of sustainable system. One of the benefits of intercropping is greater use of available resources. The aims of this study were to evaluate different tillage systems and cropping patterns of Roselle and Green Gram on some soil nutrients and the use efficiency of environmental resources. Usually, intercropping used at Low fertility soil with low input conditions in the tropics region. Bahraniet al. (2007) reported that no tillage systems compared with conventional tillage with crop residue, were increased soil organic carbon content in maize production. Ramroudiet al. (2011) expressed conventional tillage reduced amount of nitrogen compared to no tillage system.Material and Methods: The research was conducted at Zabol city. Split plot experiment performed based on a randomized complete block design with three replications. Main plot was three levels of tillage system (zero (without plowing), reduced (disk) and conventional tillage (disc plow)) and sub plot was planting ratio with five levels (pure culture of Roselle, pure culture of Green gram, 50% roselle+50% green gram, 25% roselle+75% green gram, 75% roselle+25% green gram) were considered. Preparing the ground in mid-June 2012, according to the type of plowing was performed. For comparison of means were used by Duncan's test at 5% probability.Results and Discussion: The effects of tillage systems, planting ratios and interaction of tillage systems × planting ratio on soil organic carbon and nitrogen were very significant. The highest and lowest levels of organic carbon were obtained in zero tillage (1.14%) and conventional tillage systems (0.63 %), respectively. The highest and lowest nitrogen of soil after harvest, of pure culture of Green gram (0.11 %) and 75 % of Roselle+ 25% Green gram intercropping (0.06 %) were obtained respectively, Tillage system could not affected the amount of magnesium of soil after harvest. The comparison of means showed that the highest and the lowest magnesium content were observed in conventional tillage (17.9 ppm) and zero tillage (16.7 ppm) respectively, (Table 2). The calcium amount in a pure culture of green gram (17.9 ppm) was higher than the net cultivation of Roselle (15.5 ppm). The Most of potassium soil of intercropping 25 % Roselle+75% green gram (480.1 ppm) and the lowest amount of pure cultures of Roselle (401.8 ppm), were obtained (Table 2). Bohraniet al., (2) were reported that no tillage systems compared with conventional tillage with crop residue have increases soil organic carbon content. With the increase of Roselle in intercropping reduced soil potassium and with increase the proportion of green gram in intercropping, potassium was increased. Tillage systems, planting ratio and interactions (tillage system´planting ratio) had a significant effect on soil water content and soil temperature.Comparison of means showed that maximum and minimum soil water content of the soil related to the zero tillage (18.6 %) and conventional tillage (12.6 %). soil water content pure culture of green gram was the greater than intercropping and pure culture of Roselle. Soil temperature in pure culture of Roselle was greater than of pure culture of green gram. Effect of planting ratio was significant on LER in 1% probability level. The highest and lowest of LER was obtained in 75 %green gram+25% (1.36) and 25 % green gram+75 % Roselle (1.15).Beheshti and Soltaniyan (2012) reported that LER in various combinations of sorghum and beans intercropping was higher than of unit.Conclusions: Investigation showed that the zero tillage treatments and intercropping increased the efficiency of environmental resources and improved the soil nutrient, significantly. The highest LER was achieved 75% green gram+25% Roselle, which is indicative of the excellence of intercropping compared to monoculture. The amount of organic carbon has shown an increase in soil fertility using zero tillage and increase percent of green gram in intercropping. The results showed that zero tillage systems, monoculture green gram and intercropping had soil water content more than conventional tillage systems and monoculture Roselle.

Introduction: One of the components of sustainable agriculture is multiple cropping (such as intercropping). Intercropping means the use of a farm to produce two or more crops through a year. Diversity in agricultural systems is a reason for sustainability and widespread and better production, and better use of natural resources and environment, such as water, light and nutrients has priority to monoculture. Intercropping is one of agronomical strategies to increasing the absorption and efficiency of radiation absorption and use.In proper agronomical conditions that there is no limitation for crop growth, there is a linear relationship between dry matter and absorbed radiation and the slope of regression trend line between these two indices during growing season is radiation use efficiency (RUE).Radiation use efficiency (RUE) relates biomass production to the photosynthetically active radiation (PAR) intercepted by a plant or crop. Radiation use efficiency is dependent on light, temperature, vapor pressure deficit and factors inherent to plant species. Linear relationship between biomass and accumulated intercepted radiation has been demonstrated for several herbaceous plants (e.g., beans, soybean and lettuce) and for a few tree species (e.g., willow, mesquite and juniper). The production of dry matter in conditions without any environmental stresses is a function of light absorption and efficiency of plant to production of dry matter from absorbed radiation....

Introduction: Environmental stresses affect growth, metabolism and crops yield. Drought is an important stress and it decreases crop productivity. Drought stress symptoms vary, depending on intensity and duration of drought and growth stage of the plant. The first response of plant to drought stress is producing the active oxygen species (ROS) in cell that these cause injury to membranes and proteins. Selenium (Se) application could have beneficial effect on growth and stress tolerance of plants by increasing their activity of antioxidants and reduce the reactive oxygen species over production. Selenium is essential for growth and activities of human and animals. Absorption and accumulation of selenium in plant depend on chemical compound and concentration of selenium in soil. Recent studies have demonstrated that Se increases resistance and antioxidant capacity of plants to various stress. It is reported that selenium application in barley plant no changes the amounts of malondialdehyde and hydrogen peroxide under water deficit stress. The current paper studies the response of agronomic traits of wheat and barley to sources and different rates of selenium in rain fed condition....

Introduction: Climate change has a profound influence on crop production sustainability in arid and semiarid environments. A more arid climate is usually accompanied by a higher frequency and severity of droughts.Drought prevention and mitigation has become important content of promoting economic and social sustainable development. Assessing vulnerability of agricultural crops is an effective approach in understanding the impacts of climate change and extreme climatic events on agricultural systems. In recent years vulnerability was generally considered as a function of exposure, sensitivity and adaptive capacity. Sensitivity reflects the degree to which a given system responds to the fluctuations in stress. Adaptive capacity has been defined as the capacity of a system to adjust to the change and take advantage from it. Exposure is the possibility of the system being exposed to the concerned change in the stress. This study aims to achieve an understanding of the vulnerability of wheat and maize production, to various severities of drought conditions in the past and coming future years….

Introduction: In order to evaluate the effect of foliar spraying of zinc and calcium on yield and physiological traits of safflower under lead stress, a factorial experiment based on randomized complete block design was performed in Kerman agricultural and natural resource research and education center in 2014-2015 with three replications. The first factorial included three levels (control, and 0.5 and 1 mM lead spraying), whereas the second and third factorials were spraying zinc sulfate at three concentrations (zero, and 10 and 20μM) and spraying calcium chloride at two levels (zero and 20 mM), respectively. According to the results, grain yield, the 1000-grain weight, leaf dry weight, number of seeds per head, head weight and chlorophyll content decreased. On the other hand, a significant increase was observed in the activities of catalase and ascorbate peroxidase enzymes and amount of malondialdehyde in plants. Moreover, spraying zinc fertilizer in lead treatment resulted in a significant increase in activity of catalase enzyme, reduction of membrane lipid peroxidation, prevention of chlorophyll destruction and maintenance of grain yield. However, the effect of spraying calcium fertilize in lead treatment was only significant on chlorophyll content. According to the results of the research, it seems that spraying zinc fertilizer had more effects on improved growth of safflower under lead stress, compared to spraying calcium fertilizer. Therefore, in air pollution with heavy metals (lead), application of zinc sulfate fertilizer can be an effective approach to maintain the growth and production of plants....

Introduction: Invasive plants threaten the ecosystems of agriculture, forests and rangelands. In this regard, Centaurea balsamita is an annual plant of asteraceae family that invades the fallow and slope lands. This plant is reproduced by seed and distributed in Syria, Turkey, Iran, Afghanistan and Central Asia (Turkmenistan to Tian Shan). Given that, according to studies accomplished in the world, threats of invasive plants are widely known, and since most studies related to freezing and cold stress tolerance are conducted on crop plants and there is little information about invasive plants, and considering that the precise identification of problematic invasive species. This study was performed to evaluate invasive plant Centaurea balsamita cold acclimated in spring to chill and freezing stress....

Introduction: Wheat is the oldest and most important cultivated crop in the world and has fundamental role in human food security. Drought is one of the most common environmental stresses that affect growth and development of plants. Most parts of Iran’s cultivation land are located in arid and semiarid regions and because of water deficiency, plant stress appear and wheat performance reduces severely in these regions. In such circumstances, the production of drought tolerant varieties has special importance. Understand the genetic basis of yield and yield related traits is necessary in breeding programs. One of the best approaches to determine genetic parameters is generation means analysis method, due to it allows breeders to predict epistasis. In order to estimate genetic parameters and evaluation of gene action controlling agronomic traits in bread wheat under moisture stress, F4 families derived from cross between Roushan and Kavir along with F2, F3 and parents, were evaluated under moisture stress....

Introduction: Pumpkin (Cucurbita pepo var. Styriaca) is one of the medicinal plants belonging to the Cucurbitaceae family. It is valuable in terms of seed oil and its fatty acids. The seed oil of this crop is widely used in the pharmaceutical industry. Reduction of agrochemicals (herbicides and fertilizers) is considered as research priority in medicinal plants production. Therefore, the selected practices and inputs should be environmentally sound, cost-effective and lead to high yield. Because of large inter-row space in pumpkin field, there is vast area of the bare soil which leads to weed establishment and loss of soil moisture. It seems that black plastic mulch protects soil moisture and controls weeds, thus increases seed yield. Also, biofertilizers due to available micronutrients, solubility of phosphorus, biological nitrogen fixation and phyto-hormones production increase the yield and improve the quality characteristics such as the seed oil and seed protein content.Therefore, in this research, the effect of black plastic mulch and biofertilizer on yield and quality of pumpkin under different irrigation intervals were studied.....

Introduction: Green manure is a crop used primarily as a soil amendment and a nutrient source for future crops. Leguminous green manure may add N to crop systems through biological fixation, and the slow release of N from decomposing green manure residues may be well timed with plant uptake. Leguminous and nonleguminous plants are used as green manures. Leguminous plants can form symbiotic associations with Rhizobium bacteria in order to atmospheric N fixation. This fact causes that the green manures, which their principal component are leguminous plant residue, added more nitrogen to the soil compared to non-legume. Muurinen et al. (2007) reported that strong N translocation from vegetative parts of the main shoot in wheat, which exhibited higher competition for N between vegetative and reproductive organs. Therefore, improved understanding of plant N requirements and dynamics, particularly biomass production efficiency (BPE) from vegetative parts among species and cultivars, is needed to determine better nitrogen use efficiency (NUE). So that the objective of this study was to determine the effects of legume and non-legume green manure crops in combination with different N fertilizer rates on nitrogen efficiency indices of canola.Materials and Methods: In order to study the effect of different green manure and nitrogen sources on nitrogen efficiency indices of canola, a field experiment was conducted in the experimental farm of Agricultural Faculty of Shahid Chamran University of Ahvaz during 2013-2014 growing season. The experimental was carried out as split plot based on randomized complete block design (RCBD) with three replications. The main plot was different green manure including millet, barley, mungbean, intercropping of millet and mungbean, and fallow (without green manure application). The subplot treatments were different nitrogen sources at three levels including no nitrogen fertilizer (Control), 50 % chemical nitrogen+biological nitrogen (Nitroxin) and 100 % chemical nitrogen. Nitrogen fertilizer was applied 200 kg per hectare in the form of urea. The plots of green manure were established on 6 Sep. 2010 and incorporated to the soil on 17 Oct.2013. Then canola (cv.Hyola401) was planted on 10 Nov.2013 and was harvested on 21 Apr.2014. Each plot size was 6m2 (2m´3m) that consisted of 6 rows of canola plants. Grain yield was determined by harvesting from a 2m2 area in each plot. All dry vegetative samples and also grains were first ground and then plant N concentration was determined by standard macro-Kjeldahl procedure. N content was calculated by multiplying the N concentration by dry weight. Analysis of variance was used to test the significance of data and means were compared with LSD test.Results and Discussions: The results showed that the increasing nitrogen application had negative effect on efficiency indices except of nitrogen reliance index (NRI). The highest nitrogen reliance index (NRI) (0.46 kg per kg plant) was obtained at control (without green manure and 100% chemical nitrogen) and the lowest (0.16 kg per kg plant) was revealed at mungbean intercropping with integrated nitrogen application. The highest nitrogen use efficiency (NUE) (21.4 kg per kg), and nitrogen uptake efficiency (NUE) (1.04 kg per kg) were obtained at mungbean green manure and no nitrogen fertilizer, respectively. The highest nitrogen agronomic efficiency (NAE) (24.98 kg per kg) was revealed at millet-mungbean intercropping and nitrogen integrated management. Totally the results indicated the positive effects of biological and chemical combined fertilizer and green manure plants on yield increment and efficiency indices, and decreasing of dependency on chemical inputs that it is in the way and the goal of sustainable agriculture.

Introduction: Although silicon (Si) is the second most abundant element in the earth’s crust and its content in plants often reaches values of macronutrients, it is not listed among plant essential elements. However, the beneficial effects of Si in alleviation of various kinds of biotic stresses are well known. Concerning biotic stress, Si enhances, for instance, the resistance of plants to the pathogenic fungi, and it protects plants against and various kinds of insects. Silicon can also mitigate abiotic stresses in plants. Silicon can also reduce the negative effects of some toxic metals in plant species. Cadmium (Cd) is one of the most dangerous toxic metals for living organisms. It is a hazardous contaminant of food and through the food chains enters the human body as a cumulative poison. Contamination of agricultural soils by Cd represents a serious. Environmental problem in many countries and ranks high in food safety issues. Silicon was recently described as an effective substance for alleviation of Cd toxicity in some plants. The use of nano-compound material has given a lot of attention by the agricultural researchers, especially by those investigating seed characteristics, although their exact mechanisms of actions are not well understood. Nanomaterials, because of their tiny size, show unique characteristics. For example, they can change physico-chemical properties compared to bulk materials. They have greater surface area than bulk materials, and due to this larger surface area, their solubility and surface reactivity tend to be higher....

Introduction: Deficiency of water during the plant growth is one of the main factors which reduce the crops production around the world. Drought stress is one of the most important tensions that may occur around the low rainfall, high temperature and wind blowing environments. Plant response to this stress depends on the stage of plant growth and drought intensity. Weeds are unwanted and harmful plants with disturbance in agricultural practices which make increase the cost of crop production and reduce the crop yields. Rye (Secale cereal L.) is one of the most important weeds at wheat fields in Iran (Baghestani and Atri, 2003). Low expectations, allelopathic effects and similarity of life cycle and morphology, caused increasing of rye density in winter wheat fields. Water use efficiency (WUE) as an important physiological characteristic indicates the ability of plants to water stress. WUE may be affected by climatic and soil or plant factors. In plant communities, competition is one of most important physiological topics (Evanset al, 2003). At Inter-specific competition, weeds interfere to absorbing of light, water and nutrients through the adjacency with crop and so affect the growth and yield of crops. Weeds often compete with crops for soil water and reduce the accessibility of water. Competition between weeds and crops decrease the soil moisture and cause water stress which might decrease the weeds and crops growth. When the supply of water is limited, water drainage overlap areas in soil profile could be occurred relatively fast at early of in the crop life cycle....

Introduction: Roselle (Hibiscus sabdarjffa L.) is an annual or biennial plant cultivated for its stem, fiber, edible calyces, leaves and seeds and belongs to themalvaceae family. Sepals of Roselle have good color and are potential source of antioxidant compounds, Studies conducted on medicinal plants in natural ecosystems suggest that using sustainable agricultural system provides the best conditions for the production of these plants, leading to maximum qualitative and quantitative yield in such conditions. Roselle is one of the plants that needs less water and is resistant to drought. It can be used as a suitable plant for cultivation in southern areas of Iran that face water scarcity.Materials and Methods: In order to evaluate the effects of fertilizer resources and different irrigation regimes on yield, yield components, antioxidant activity and calyx anthocyanin content of Roselle (Hibiscus sabdariffaL.), an experiment was conducted at Agricultural Research Farm of Jiroft University in 2013 and 2014 growing seasons. An experiment was conducted as strip plot based on a randomized complete blocks design with three replications. Three irrigation regimes (100, 80 and 60% ofcrop water requirement) were assigned ashorizontal factor and four fertilizer resources (mycorrhiza, vermicompost, cow manure and chemical fertilizer (NPK)) were allocated as vertical factor. Plant water requirement was calculated by AGWAT software.Then, treatments of 80 and 60 percentage of water requirement was determined and irrigation water was recorded in each irrigation period using water meter. The antioxidant activity and anthocyanin content of Roselle calyx were determined using the method described by Abeet al., (1998) and Wanger (1976), respectively.Finally, data analysis was done using SAS 12.5 and means were compared by LSD’s multiple range test at 5% level of probability.Results and Discussion: Based on two years data combined analysis, the results indicated that fertilizer resources and irrigation levels had significant effect on plant height, Inflorescence length, number of bolls, boll dry weight, calyx yield, biomass yield, anioxidant activity and anthocyanin content. Calyx harvest index was not affected by fertilizer resources and irrigation levels. The interaction effect of fertilizer resources and irrigation regimes had a significant effect on calyx yield. The evaluation of anthocyanin value at different levels of irrigation showed that, except for in time of using vermicompost, anthocyanin value at the irrigation level of 60% was higher than irrigation levels of 100 and 80% of plant water requirement in combination with other different nutrition sources. The highest anthocyanin value was found in the control treatment when it was under moisture level of 60 percent. It has been stated that flavonoid increased under the water shortage and drought, leading to production of anthocyanin pigment. In a study conducted on Roselle, it was found that applying biofertilizers alone or in combination with chemical fertilizers increased carbohydrates and anthocyanin content.The highest calyx yield (1248 kg ha-1) was obtained at 100% crop water requirement+cow manure treatment and the lowest calyx yield (510 kg ha-1) was obtained at 60% crop water requirement+control treatments.Conclusions: It seems that cow manure and vermicompost can have a positive impact on soil water holding capacity compared to other sources of fertilizers (mycorrhiza and chemical fertilizer) by increasing soil organic matter. Although mycorrhiza can have positive effects on plants growth, it seems that under this experiment, air temperature and low moisture holding capacity and organic matters of soil lead to a reduction in the positive effects of these soil organisms.

Introduction: Nitrogen is one of the most abundant elements on earth and major essential for crop growth and development that is heavily used in modern agriculture to maximize yields. Among cereals, maize (Zea maysL.) is an important food and feed crop which ranks third after wheat and rice in the world. As N fertilizer costs remain relatively high and environmental concerns over excessive N application increase, the objectives of the present study were: (i) to compare maize hybrids growth and yield responses to N rates, (ii) to determine optimum N rate for maize grain yield production, (iii) to explore the physiological functions controlling maize growth and yield and (iv) to identify more effective physiological indices in maize grain production under N stress as well as potential condition....