In order to study light Competition in mixed canopy of wheat and weeds, two experiments were conducted in Ferdowsi University of Mashad, Iran during 2000-2001 cropping season (field study), and Guelph University, Ontario, Canada (2002), (growth cabinet study). The treatments of the field study included three levels of Cruciferous weeds (wild mustard, turnip weed and flix weed) and five levels of weed density (0,4, 8, 16 and 32 plants/m2 for wild musturd and turnip weed, and 0, 16, 32, 64 and 128 plants/m2 for flix weed). Randomized complete block design with four replications in an additive series technique with fixed no. of 450 wheat per square meter was employed as the experiment design. In growth cabinet study, is used a model system of annuals to examine how canopies of species having differing morphologies differed in light-interception. Wheat, wild mustard and flix weed were grown as "targets", surrounded by neighbours of a single species. Neighbours could be anyone of the target species. Plants were grown in pots, with one target plant and three neighbors plants. Results of experiment indicated that wild mustard and turnip weed (in comparison to flix weed) had more effect on PPFD and R: FR. In addition, with increase in leaf area of mixed canopy, the quality and quantity of light changed.      

Growth analysis will help to achieve a better understanding of the effects of different environmental factors such an weeds on the yield of crops. To examine the above hypothesis an experimental research was conducted on soybean in Eahi-Mahaleh Reseach Station in Golestan Province in 1997. Treatments were divided in two groups. The first group comprised of soybean plots which were kept weed infested up to V1, V3 , V5,V7,R1, R4 and R8 growth stages and the second group were kept weed free up to the same growth stages. Fourteen treatments were arranged factorially in a complete Block Design with four replications. Seed yield, number of pods per plant, number of seeds per pod and 1000 seed weight was measured. Growth indices such as Leaf Area Index, Crop Growth Rate and Leaf Area Ratio were also calculated.Number of pods per plant was the most important yield component which showed a strong positive correlation with seed yield. There was little reduction in number of seeds per pod and 1000 seed weight due to weed Competition. Seed yield was affected by weed Competition and was significantly reduced as weed Competition continued to the later stages of soybean growth. Leaf Area Index and Crop Growth Rate significantly reduced as weed Competition continued, but Relative Growth Rate, Net Assimilation Rate and Leaf Area Ratio were not affected by weeding time. The changes in growth characteristics well defined changes in soybean yield.

This experiment was conducted to investigate the effect of nitrogen on yield and nitrogen use efficiency of corn genotypes under the conditions of Competition with weeds and as split plots in a randomized complete blocks design with four replications. In the main plots, three amounts of nitrogen fertilizer (90, 180 and 260 kilogram net nitrogen per hectare from source of urea (46 percent nitrogen) and without fertilizer, and in the subplots of four corn hybrids SC. 704, DKC6589, Mobin and SC. 640 were compared. Each sub plot was hypothetically divided into two weed free and with weed equal parts. The results showed that nitrogen application efficiency in plots with weeds was significantly decreased. The presence of weeds caused the average weight of 100 seeds, grain yield and biological yield to be reduced by 5. 3, 21. 7 and 24 percent, respectively, in comparison to weeding conditions. The use of nitrogen fertilizer up to 180 kilogram per hectare increased the grain yield of all genotypes under conditions of Competition with weed. In conditions of Competition, the performance of all genotypes with the exception of DKC6589 line decreased at 260 kilogram nitrogen per hectare treatment as compared to 180 kilogram nitrogen per hectare treatments. So that in the weed presence conditions, the average corn yield increased by 50 and 30 percent in 180 and 260 kilogram nitrogen per hectare in fertilizer treatments, respectively. The highest grain yield in both conditions of Competition and weeding of weeds (908 and 1222 kilogram per hectare, respectively) was allocated to DKC6589 line. Increasing nitrogen rate increased the mean plant height of corn genotypes in both Competition and weeding conditions. Plant height, ear height from the surface of ground, and the number of leaves of DKC6589 line was significantly higher than other corn genotypes. Plant height, ear altitude from the ground and leaf number of DKC6589 were significantly higher than other hybrids.

An experiment was conducted to determine the best index for predicting wheat yield loss at the beginning and end of the growth season, estimation of quantity and portion of any of the weeds in interference with wheat, conducted in the research agriculture station in Islamic Azad university of Ghaemshahr in 2002. For this purpose, dimension of field 24*35 meter was chosen. In this area, four strips with 35 meters long with 6 meters wide was chosen, equal to the position - sprayer. Then each strip was accidentally allocated to one of the f91l6wmgtreatments: Un controlling the weeds, controlling the narrow leaves weeds, controlling the wide leaves weeds, and controlling all of the weeds with using the suitable herbicides. Any strip was divided to two sections in lengthwise; in first section, density, leaf area and dry weight of wheat and weeds measured at the beginning of the season while in the second section these variables were measured during the harvest. The results show that at the beginning of the growth season, the best index to predict the wheat yield is wheat and weed relative leaf area, while at the end of the season it is for the leaves weight. The model which was used to explain the Intra-species and inter-species Competition was based on the wheat grain weight reciprocal law. The model evaluation about independent variables of four species including Triticum aestivum, phalaris sp., Descurainia sophia and veronica persica at the beginning of the growth season showed that phalaris sp. could meaninglessly increase wheat growth and yield. More over, partial coefficient detennination was used to review the portion of any ariables (species). Among the wide leaf weeds, the most inhibition was allocated to the Descurainia sophia and the portion of the inter-species Competition for reduce wheat yield was more than wheat intra species Competition.

In order to study the weed damage and to determinate the influence of weed species and multiple weed species Competition in corn (Zea mays L.), a field experiment was conducted based on interval mapping at the Agronomy Research Field of Ferdowsi University of Mashhad during 2009-2010. Treatments consisted of four density level of crop (5, 6, 7 and 9 plant.m-2) and four type of weed management (completely removed weed, broadleaf control, non control, and grass weeds control). Weed samples were taken at harvest time. Dry matters of corn samples were measured. The Density and dry matter of weed samples were recorded separately for each species. Equations were fitted single plant weight ln of each weed species or crop as dependent variable to compare and evaluate the Competition coefficient of inter and intra species. Results indicated that single plant weight ln and plant density per m-2 had high correlation to evaluate Competition coefficient. Considering the coefficients of equation the function of single plant weight ln showed that crab grass and prostrate pigweed had the most stimulation effect on corn. While redroot pigweed prostate common purslane field bindweed black night shade common lambsquars barnyardgrass purple grown nutsedge and Green foxtail had inhibition effect on corn. The positive of the former group on corn were resulted from the inhabitation effect on the latter group of weeds.

In order to study the effect of different weed Competition periods on sunflower yield, cv. Allstar, an experiment was conducted in Islamic Azad University of Tabriz, Iran, during 2007 based on randomized complete block design with three replications. The first five treatments were the presence of weeds in the first 2, 4, 6, 8, 10 weeks and their subsequent control during the remaining growth season. The sixth treatment included the preservation of weeds in the whole growth period. The seventh treatment was chosen as a control and the weeds, in the whole period of growth, came under the control. Dominant weeds in experiments were redroot pigweed (Amaranthus retroflexus L.), lambsquarters (Chenopodium album L.), bermuda grass (Cynodon dactylon L.) and small bindweed (Convolvulus arvensis L.). Results showed that the effects of treatments on leaf area index (LAI), anthodium diameter, grain number per anthodium, hollow seed percentage, hundred seeds weight, seed grain yield and seed oil yield were significant. Reduction value in LAI was calculated 54%, when weeds Competition with sunflower extended along it' s growth period. Simultaneous growth of weeds and sunflower for more than 8 weeks could reduce grain number per anthodium, significantly. Grain yield of sunflower in full season weeds interference reduced to 27.5%, compared with control. With attention to oil yield reduction of sunflower from 29%, when weed control delayed until 4 weeks after sunflower emergence, to 43% in full season Competition of weeds in present weed densities, weed control is recommended, when they grow simultaneously with sunflower more than 2 weeks after sunflower emergence.

Background and Objectives: Plant nutrition is an important factor in the growth and chemical composition of plants. The application of natural fertilizers can enhance the performance and pharmacological properties of plants. Rosemary (Rosmarinus officinalis L. ) belonged to Lamiaceae family. Application of chemical fertilizers causes environmental pollution and ecological damage. One of the solutions to these problems is the use of sustainable agriculture principles in agroecosystems, including the use of organic fertilizers such as vermicompost and manure fertilizer. Considering the mentioned issues and taking into account the importance of rosemary herb and the management of weeds in agricultural landscapes, which is one of the biggest problems faced by farmers, this experiment was carried out with the aim of investigating the effect of fertilizer sources on biochemical characteristics and yield of rosemary in Competition and non-Competition with weeds conditions. Materials and Methods: This experiment was conducted as a split plot in a randomized complete blocks design in three replications at Sari Agricultural Sciences and Natural Resources University in 2016. The treatments consisted of Competition between plants and weeds (weedy and weed free) as a main factor and sub factor was fertilizer sources include sheep manure (20 ton ha-1), vermicompost (10 ton ha-1), sheep manure (10 ton ha-1) + vermicompost (5 ton ha-1), NPK fertilizer, NPK nanofertilizer and control (no fertilizer). The studied traits included: photosynthetic pigments (chlorophyll a, b, total and carotenoid), total phenol, total flavonoids, antioxidant activity, nutrient content (NPK), yield of rosemary and weeds biomass. Results: The results showed that treatments had a significant effect on all traits. highest levels of chlorophyll a (7. 24 μ g ml-1), chlorophyll b (2. 66 μ g ml-1), total chlorophyll (10. 08 μ g ml-1) and carotenoid (2. 19 μ g ml-1) was observed in vermicompost treatment, which was happen in weed free condition too. Maximum amount of total phenol (70. 85 mg g-1 leaf dry weight), total flavonoid (46. 43 μ g ml-1 leaf dry weight) and antioxidant activity (91%) were observed in sheep manure with weed interference, sheep manure with weed interference and vermicompost without weeding, respectively. While, maximum amounts of nitrogen (1. 65%) and potassium (1. 90%) were seen in vermicompost in weed free condition and for phosphorus (1. 26%) in sheep manure with weed free, respectively. The highest weeds biomass was observed in chemical fertilizer treatment in all three sampling. Conclusion: The results of the experiment indicated the superiority of organic fertilizers to chemical fertilizers, as well as the positive response of rosemary to fertilizer application. Non-use of chemical inputs in the production of medicinal plants and their products is a prerequisite for their health and naturalness. Therefore, considering the positive response of rosemary herb to the use of organic fertilizers, seems that the application of these fertilizers, reduced the use of chemical fertilizers and have no environmental consequences, decrease weeds biomass and reduces weed damage, as well as reducing herbicide use; therefore it is a good way to produce healthy and sustainable products of these species.

In order to determine effects of weed Competition on canopy architecture of wheat, an experiment was conducted in Mashhad, 2001 and 2002. The treatments included three Crucifer’s family weeds (Wild mustard. Turnip weed and Flix weed) and five levels of weed density (control, 4, 8, 16 and 32 plants/m2 for wild mustard and turnip weed, and control, 16,32,64 and 128 plantlm2 for Flix weed). Randomized complete block design with four replications in an additive series technique was employed as the experimental design. An ANOVA procedure indicated significant effects of wild mustard and turnip weed on plant height, leaf area and leaf distribution of wheat. Increasing weed plant density, reduced the height and leaf area of wheat. In addition, in comparison with control, leaf area of wheat was more distributed in the upper part of the canopy. As plant density of weeds increased, their plant height also increased and more leaf area was measured in the upper part of weeds conopy.

Quinoa is a pseudo cereal from Amaranthaceae family, which is currently considered as a suitable alternative for plants with high water consumption due to its high nutritional value and stresses tolerance, especially drought and salinity. Meanwhile, reduction in crop yield caused by weeds competing for water, light and nutrients is well known. Hence, a study was conducted in Karaj to investigate the competitive capacity of quinoa with weeds under normal irrigation and drought stress and also to determine the required time for weed control. The experiment was arranged in split plot randomized complete block design with four replications consisted of irrigation levels (60, 80 and 100 mm evaporation from the evaporation pan) as main plots and weed control levels (0, 7, 14, 28 days of control and control in all seasons) as subplots. The highest quinoa grain (331 g/m2) and biological yields (1262 g/m2) were obtained under normal irrigation in weeds free treatment. Also, the lowest grain and biological yields were 139 and 723 g/m2, respectively that obtained under high drought stress in weeds infestation during growing season. In one month weeds free treatment under medium drought stress, grain and biological yields were 290 and 1010.25 g/m2, which show that despite the competitive potency of summer weeds, quinoa has good competitiveness in drought stress, and with one month of weed control, can achieve performance close to full control. In logistic model fitting to the grain yield, the maximum and minimum values of y0 and a, i.e. upper and lower limits, were observed in normal irrigation and high drought stress, respectively; although, the maximum and minimum values of GDD50 were obtained in high drought stress and normal irrigation, respectively.