جستجوی مقالات مرتبط با کلیدواژه "competition" در نشریات گروه "اکولوژی"

This research was carried out in order to evaluate the effect of intercropping of replacement and addition series on the yield and yield components of Camelina and Lentil under rainfed and irrigated conditions.

The experiment was carried out in the form of split plots in the form of a basic design of randomized complete blocks with three replications in the research farm of the Faculty of Agriculture of Ilam University in growing season in 2020-2021 and 2021-2022. The main plots include irrigation on two levels (rainfed and irrigated) and the subplots include alternative and incremental mixed cropping patterns in nine levels including (75% Camelina+ 25% lentils, 50% Camelina+ 50% lentils, 25% Camelina+ 75% lentils), 100% Camelina+ 25% lentils, 100% Camelina+ 50% lentils, 100% Camelina+ 75% lentils, 100% Camelina+ 100% lentils, monoculture of Camelina and lentils).

The results showed the highest grain yield (1827 kg ha-1) and biological yield of camelina (7012 kg ha-1) in the series of 100% camelina+ 25% lentil and the highest grain and biological yield of lentil was 750 and 1950, respectively, related to monoculture lentil cultivation. The evaluation of the ratio of land equality showed the superiority of all ratios of camellia and lentil intercropping over their monoculture, and the incremental rows of 100% camellina+ 75% lentils and 100% camellina+ 100% lentils had the highest LER.

The results showed that the intercropping of camelina and lentils under irrigation and rainfed conditions was beneficial and superior compared to their monoculture.

Intercropping cultivation is an excellent method to increase agricultural productivity per unit area based on environmental mechanisms. In this planting system, it is necessary to select crops with different capabilities in uptake resources and establish a complementary relationship. However, legumes in intercropping cultivation can be used an alternative and sustainable way to increase efficiency. Besides, it is necessary to study the interactions in the above and belowground parts to achieve the mentioned goals. Therefore, this study aimed to investigate inter-specific interactions in millet and soybean intercropping cultures.

A field experiment was conducted for two years (2018-19) at the research farm of Sari agricultural science and natural resources university, Iran (33º, 36ʹ N, 53º, 03ʹ E with 43 m altitude). The experimental design was a randomized complete block with four replications. The experimental treatment was 75% Soybean + 25% Niger, 50% Soybean + 50% Niger, 25% Soybean+75%Niger based on the replacement method and monoculture. This study investigated the agronomic traits, LAI, TDW, nitrogen derived from the atmosphere, and total microbial activity in the soil in different planting ratios.

The results showed that soybean monoculture had the highest plant height during different stages of growth. Furthermore, with the increase in the share of planting soybean in intercropping cultivation, the shoot height of the millet also increased. Also, unlike the millet, the soybean succeeded in producing more leaf area indexes among different mixed cultivation ratios than monoculture. The leaf area index of millet showed a significant decrease as the proportion of soybean plantings increased. However, despite this decrease, the total dry matter of soybean exhibited a higher percentage increase at various growth stages compared to the decrease in millet yield. As a result, after 60 days of planting, the intercropping cultivation of millet and soybean demonstrated positive complementarity in terms of competition impact. Additionally, the intercropping cultivation showed a higher percentage of nitrogen derived from the atmosphere compared to soybean monoculture. During the study period, the planting ratio of 75% millet and 25% soybean exhibited the highest increase in nitrogen fixation (Ndfa), with average values of 93.84% and 83.85% at 90 days after planting, respectively. Increasing the number of millet sowing rows in the intercropping patterns played a crucial role in intensifying competition with soybeans during the early growth stages and had an impact on the biological activity of soybeans. Moreover, the microbial activity in the soil (at a depth of 0-30 cm) was higher in the different intercropping ratios compared to monocultures of soybean and millet. In addition, soybean and millet monoculture had the highest and lowest grain yields. Among the different intercropping ratios, the 75:25 in 1398 with an average of 4639.77 kg. ha-1 had the highest grain yield. Besides, the planting ratio of 25:75 and 50:50, with an average of 1.23 and 1.02, respectively, had an LER higher than one. With increasing the share of soybean planting in intercropping, the competitiveness of the plant increases, and the competition ratio of millet was higher than the unit only in the planting ratio of 25:75 (millet-soybean). Therefore, the competitiveness of millet in mixed cultivation is significantly reduced by reducing the share of planting row. Finally, increasing productivity in the 25:75 combinations reduced soybean's competitive dominance, increasing millet grain yield in comparison to expected values and improving total microbial activity.

Due to limited growth period, millet had competition played an essential role in increasing total microbial activity and the percentage of nitrogen derived from the atmosphere at a 25:75 planting ratio before the initial reproductive growth. In addition, 25:75 and 50:50 planting ratios reduce soybean's competitive dominance, resulting in enhanced productivity. Finally, the selection of complementary plants based on physiological, morphological characteristics, and competitiveness in intercropping cultivation can be effective in the above and belowground interactions.

Weeds control is very important to achieve optimal yield in agricultural products. The purpose of this study was to determine the critical period for weed control (CPWC).of garlic in chemical and organic nutrition management in Ramhormoz.

A factorial experiment based on randomized complete block design (RCBD) was carried out in 2019—2020 with three replications in Khuzestan-Ramhormoz province. The first factor included nutritional management (chemical and organic) and the second factor included 12 treatments of interference and control period of weeds (0, 20, 40, 60, 80, 120 and 160 days).

Determining the critical period of garlic weed control in two chemical and organic nutrition management revealed that the beginning of the critical period in organic application will be happen later than chemical fertilizers. Also, the end of the critical period in chemical application of was predicted later than fertilizers. Also, the end of the critical period in application chemical was predicted later than organic fertilizers. The length of the critical period for weed control was higher than in chemical than chemical application compared to organic fertilizers. With 5% loss yield, the beginning, end and length duration of the critical period for weeds control in organic management were 202, 1518 and 1316 GDD and in application chemical fertilizers were estimated 210, 1638 and 1428 GDD respectively.

The results indicated that length duration critical period for weed control in organic nutrition management (120 days) will be shorter than chemical management (127 days).

This study was performed to investigate the response of three rice cultivars in competition with barnyard grass densities and to select a suitable cultivar with the ability to more competitive. The experiment was conducted as a factorial arrangement based on randomized complete block design (RCBD) with three replications in Babol, Iran, in 2018. Factors included rice cultivar (Tarom Hashemi, Fajr, and Neda) and barnyard grass density (0, 10, 20, 30, and 40 plants m-2). The results showed that the Biomass of barnyard grass and rice yield were affected only by the simple effects of rice cultivar and barnyard grass density. The Biomass of barnyard grass in Fajr and Neda cultivars compared to the Tarom Hashemi cultivar decreased by 28 and 35%, respectively. The amount of barnyard grass biomass increased by 18, 49 and 67% at densities of 20, 30 and 40 plants compared to the density of 10 plants m-2 of barnyard grass. The highest and lowest rice grain yield was obtained in Neda (779 g m-2) and Tarom Hashemi (297 g m-2) cultivars, respectively. The amount of increase in rice grain yield in Fajr and Neda varieties compared to Tarom Hashemi cultivar was 133 and 162%, respectively. Also, grain yield decreased up to 2, 7, 12, and 24%, respectively, at 10, 20, 30, and 40 barnyard grass m-2 with 493 g m-2.

Competition is an interaction between a species’ members or different species under the ecological needs to use the same resources. The present research aimed to quantify the competition in a mixed stand in the Arasbaran forest. Sampling was a distance method. The diameter at breast height, total tree height, two diameters of the tree's crown, and the distance of the trees were measured (one tree as the target and four neighboring as the competing trees). Data was analyzed using the distance-dependent and distance-independent competition indices. The results showed that the distance indices value were 0.29 to 31.71 and distance-independent indices were 0.94 to 4.43. There was a significant negative correlation between the stand quantitative characteristics and the distance between trees with the value of distance indices in most cases. The correlation between canopy diameter and area with distance indices was positive and significant, but with distance-independent indices was slight and not significant. Competition quantification in mixed stands will provide to know the relationship between the amount of competition and the quantitative characteristics. Consequently, and can provide knowledge for silvicultural treatments, and forest management strategies to balance the competition level in natural stands to reach the desired mixed structure.

The aim of this study was investigated the effect of weed interference on some growth indices and grain yield of corn (Zea mays L.), an experiment was carried out in a randomized complete block design with four replications during 2019 growing seasons at the Moghan region.

The experiment was included fourteen treatments; seven weed-infested and seven weed free treatments were applied at regular intervals (0, 10, 20, 30, 40, 50 and 60 days) after corn emergence in which weeds were allowed to grow until harvest and weeds were removed, respectively. Total dry weight of weeds, total dry matter (TDM), leaf area index (LAI), crop growth rate (CGR) and yield of corn were measured.

The results showed that all measured traits were affected by weed interference duration and weedcontrol period. Weed interference duration increased total dry weight of weeds and weed-free duration reduced total dry weight of weeds. Also, increase in weeds interference duration significantly reduced TDM, LAI, and CGR and grain yield of corn. On the other hand, TDM, LAI CGR and grain of corn increased by rising weed-free duration.

Considering of 10% yield loss, the critical period of weed control was 3 and 52 days after corn emergence, respectively. The weed interference duration had a significant effect on grain yield of corn and weed interference at the whole season. Weed interference reduced grain yield of corn.

In order to investigate the weed interference duration on some growth parameters and yield of potato (Solanum tuberosum L.), an experiment was carried out in a randomized complete block design with four replications during 2017 in Ardabil region.  

The experiment was included twelve treatments; six weed-infested and six weed-free treatments were applied at regular intervals (0, 10, 20, 30, 40 and 50 days) after potato emergence in which weeds were allowed to grow until harvest and weeds were removed, respectively. Total dry matter (TDM),leaf area index (LAI), leaf area index duration, number of branches, mean tuber weight and tuberyield of potato (Solanum tuberosum L.) were measured.  

The results showed that all measured traits were affected by weed interference duration and weed control period. Weed interference duration increased total dry weight of weeds and weed-free duration reduced total dry weight of weeds and mean tuber weight. Also, increase in weeds interference duration significantly reduced total dry matter, leaf area index, leaf area index duration, number of branches, mean tuber weight and tuber yield of potato. On the other hand, total dry matter, leaf area index, leaf area index duration, number of branches and tuber yield of potato increased by increased weed-free duration.  

Considering of 10% yield loss, the critical period of weed control was 18 and 57 days after potato emergence, respectively. The weed interference duration had a significant effect on the final yield of potato tubers and the interference duration through whole season caused 59.7% yield loss as compared to the control.

Rice is a global important food and in Asia alone is the source of food for 3.5 billion people. Such demand for rice imposes a plan to find new technology and approaches to replace old production methods. About 75% of global rice production is practiced on low lands. At field scale, rice compared to other plants receive two or three times more water and based on some calculations, about 34-43 percentage of global irrigation water or 24-30 percentage of drinking water consumed by rice plant. In this situation, the most important challenge with regard to rice production, water storage, increased water productivity and rice production is less than water. Recently, rice production systems such as rice alternate irrigation, where less water can be produced, has been considered as rice increasing demand for water in industry and cities have imposed the reduction of water consumption for agriculture. Rice is one of the most sensitive plants against water scarcity as a floodplain plant and has the most need for water in the cereals. Rice has the highest crop area than other irrigated plants.

This experiment was conducted as split-plot, using irrigation as main-plot at five levels (full irrigation, irrigation at ever 5, 8, 10, and 15 days), and planting distance as sub-plot at four levels (20x20, 25x25, 30x15, and 30x20 cm) within format of random complete block design with three replications. The study was performed in two years (2016-17, 2017-18) in national rice research center. Soil samples were taken to determine the soil tissue, soil water holding capacity, and some chemical characters including EC, PH, and amount of Ca, Na, and Mg. Within firs 15 days after transplanting, the rotation irrigation was not employed so the plant be able to establish in the field. The plowing was performed in two times. The first plow in the late autumn and early winter and the second plow were perpendicular to the first plowing in the spring. Fertilization was done based on long term local practice. Transplanting was done in may, 15 and at this time transplants were 20-25 cm height carrying 4-5 leaves. All traits including stem and leaf dry matter, leaf area index (LAI), crop growth rate (CGR), net assimilation rate (NAR), leaf area ration (LAR), relative growth rate (RGR) and specific leaf area (SLA) were measured and calculated. SAS and SPSS software’s were used for analysis of variance. Excel software was used for drawing slices.

ANOVA results showed that interaction of irrigation and planting distance were significantly (P <= 0.01) affected leaf and stem dry matter, LDW, TDW and CGR Individual effects of each treatment significantly affected the LAI and NAR but did not affect LAR, LWR, RGR, and SLA. As light absorption i a limiting factor in crops production, then where is no other environmental stress, increasing light absorb will increase crop production. In contrast to other crops light capture competitions a major issue for rice. Increasing panting density, vegetative growth and LAI would be lower and as planting density decreases, due to availability more spaces, both vegetative growth ad LAI increased.

 In general, this study results showed that rotation irrigation significantly affected the rice growth indexes, and reduction levels of study traits depends on irrigation timing at growth stage. Planting distances showed that planting at 20x20 cm, provided the most optimum conditions for rice plants under different stress, the worst conditions resulted in 25x25 cm planting distance. At lower planting density, due to lower competition between plants till flowering time but after this stage, competition for photosynthetic materials increased among the seeds which can result in small dead seeds.

For increasing sunflower competitiveness to weeds, potential of production and water-nitrogen use efficiency through intercropping of bean and soybean under conservation tillage system, an experiment was conducted at the Agricultural Research Station, Faculty of Agriculture, Bu-Ali Sina University, during 2013 and 2014 growing seasons. Experiments were conducted as split plot based on randomized complete block design with three replications. Tillage as conventional tillage, reduced tillage by chisel and reduced tillage by disc) and different planting patterns :sunflower sole cropping with weeding, sunflower sole cropping without weeding, additive intercroppings of 30, 60 and 90%bean, as well as 30, 60 and 90%soybean with sunflower were considered as main plots and sub-plots, respectively. Results showed that the highest total weed density and biomass values were observed at reduced tillage and sole cropping treatments. However, conventional tillage and intercropping system were able to decrease density and biomass of dominant weeds, such as pigweed, foxtail and bindweed. Considering to the increasing total yield of intercropping (the sum of the yield of main and associated plants), these systems increased water and nitrogen use efficiency in comparison with sunflower sole cropping without weeding. The land equivalent ratio (LER) was calculated to measure efficiency of intercropping compared to sole cropping. Based on our findings, >30%bean: sunflower or >30%soybean: sunflower combination showed grain yield advantage (LER>1). In conclusion, our results suggest that under similar and favorable conditions, applying a combination of conservation tillage and intercropping to sunflower cultivation can improve weed management and increase the economical yield and land use efficiency when compared to sunflower sole crop under conventional tillage.

Weed–crop competition as one of the main reasons for crop loss is often influenced by many factors including emergence time and density of competing species. Patterns of weed seedling emergence affect the outcome of weed–crop interference interactions. Information on weed seedling emergence in relation to crop seeding will assist in developing an optimum weed control program.Weeds emerge simultaneously with a crop, have the greatest potential impact on crop production. Results from Chauhan & Johnson (2010) showed the advantage for weeds over rice in situations where these species emerge earlier in the growing season because of significantly greater biomass production comparing to those emerging later in the season. Minimal shading and competition for nutrients and soil moisture are associated with early emergence.The importance of density in competition studies is because of the relationship among plant yield, number of individuals, and resources present. Increasing the density may enhance the plant’s share of the total resource pool and reduce resource availability for adjacent plant. Thus, to analyze competition between the crop and weeds, the variation in density should be considered. Season-long competition with watergrass at densities of 86 and 36 plants/m2 reduced rice yields by 59% and 46%, respectively.Understanding relative aggressiveness of component species is required for the integrated weed management and it would improve weed management strategies. For watergrass as a relatively new-introduced weed species in paddy rice fields of Guilan province, it is essential to investigate the effects of the emergence time in nursery, to determine weed seedling ages at the time of transplanting, as well the amount of weed seedling translocation characterizing weed density in the field.

Factorial arrangements of watergrass seedlings ages at the time of transplanting (10, 20 and 30 days), and plant proportions of weed:rice (0:4, 1:3, 2:2, 3:1, and 4:0) were designed as a randomized complete block with three replications to study yield characteristics and competitive ability of watergrass and rice over two years of a field experiment. Individual plants of each hill constituted as a single experimental unit. The area between individual hills was hand-weeded to avoid competition from other species. At rice maturity stage, plants were harvested, and rice and watergrass panicles were separated from stems by hand. Panicles were dried to a constant weight at 75 ℃, and weights were determined. Grain weights standardized to 12% moisture content. Biological yields of rice and watergrass were also measured after sampling their above-ground parts from an area of 1 m2 and drying at 75 ℃ until constant weight. Data were subjected to ANOVA, and means were separated using Fisher’s Protected LSD at P < 0.05. Competitiveness of the species was assessed based on the relative yield (the ratio between the production of the species in the mixture and in monoculture), relative yield total (total relative yield of the two associated species), aggressivity index and replacement series diagrams (models describing the possible outcomes of the interaction of two species when grown in a replacement series).

For each species, the greater ratio at the planting proportion, the higher biological yield, grain yield, relative yield, and aggressivity index, but the lower harvest index. When grown in monocultures, and 1 weed: 3 rice of the second year, the two species produced similar grain yield; however in the other mixtures watergrass produced more biological and grain yield compared to the rice. Harvest index of rice was greater than watergrass in all planting proportions. In the first year, trials of 30-day watergrass seedling ages represented the highest values of biological-, grain-, and relative yield, and the lowest values of grain and relative yield of rice and harvest indices of both species. Also, for all watergrass seedling ages in both years, weed production was more than rice.

Investigating grain and biological yield, and relative yield of both species, and aggressivity index of rice, beside replacement series diagrams exhibited higher competitiveness for watergrass comparing to rice. Therefore, it is important to maintain watergrass control in order to insure the sustainability of transplanted rice production.

The critical period of weed control in cumin (Cuminum cyminum) were determined by field study in 2011 in Sabzevar. Experiment was conducted in randomized complete block design with 3 replications. Treatments were weeding at 15, 30, 45and 60 days after emergence during the growing season (weed free), and 15, 30, 45and 60 days without weeding (weed infested) in the growing season and includes free of weed and weed infested in the entire growing season. Beginning and end of the critical period of weed damage were determined by Gompertz and Logistic equations. The results showed that weed dry weight was significantly increased with increasing duration of infection and reduce weed-free period. Full-season weeds interference reduced plant height (11.29%), number of lateral branches (39.14%), number of umbels (46.87%), number of seeds per umbrella (43.12%), seed yield (48.99%), biological yield (48.99%) and essential oil yield (26.94%) compared full season weed-free plots, respectively. Based on 5 and 10% acceptable seed yield losses, the critical period of weed control was 9-76 and 12- 63 days after planting at rain-fed condition.

The effect of planting time of cover crops on soybean -weed interaction, was assessed by experiment based on randomized complete blocks design with three replications in juybar during growth season of 2013. Treatments were included cover crops fenugreek (Trigonella foenum–graecum L.), winter veteh (Vicia sativa L.), Persian clover (Trifolium resupinatum L.), and chickling pea (Lathyrus sativus L.) simultaneously and three weeks after soybean sowing as well as two soybean cultivars under weed and non-weed conditions. The lowest yield of soybean was observed in weed infestation (7449.4 kg.ha-1) and the highest yield of soybean (3792.69 kg ha-1) was observed in the second planting date of winter veteh. While, maximum cover crops height, stem diameter, leaves number, dry matter and leaf size were observed at the first planting date of them. Meanwhile, at all three sampling stages, the infested soybean with weeds had the highest density and weed biomass, and the lowest weed density and biomass were also observed in winter veteh cover crop at the second planting date in all three stages. It seems that winter veteh as a living mulch can reduce the weeds growth with accelerating canopy closure; also, decreasing weeds competition with the main crops, incrased, crop yield.

  Medicinal plants are in use by a large portion of population for their medicinal therapeutic effects. Borage (Borago officinalis L.) is an annual herbaceous, and hairy medicinal plant which height changes within 70 to 100 cm. Stems are straight, often branched, hollow, and covered by tough fibers. Its leaves are alternate and simple and are covered with tough fibers. The flowers are blue and rarely appear white or rose colored. This plant belongs to the family of Boraginaceae. The plant is also commercially cultivated for borage seed oil extracted from its seeds. Water is one of the important factors affecting growth and yield of medicinal plant. Increasing plant production per unit of water is one of the greatest challenges facing the researchers especially in arid and semi- arid regions. Plant density is an important agronomic factor that manipulate micro environment of the field and impacts growth, development and yield of plants. Within certain limits, increase of plant population density decreases the growth and yield per plant but the reverse occurs for yield per unit area. The optimum plant density to attain highest yield may vary with the plant and geographical location. Present study aims to investigate the possibility of improving the yield and yield components of borage affected as irrigation levels and plant densities. A field experiment was conducted as split plot experiment based on a complete randomized block design (CRBD) with three replications at Agricultural Research Station, College of Agriculture, Ferdowsi University of Mashhad, Iran, during growing season of 2012-2013. Three irrigation levels (1000 (I1), 2000 (I2) and 3000 (I3) m3.ha-1) and four plant densities (16 (D1), 20 (D2), 26.67 (D3), 40 (D4) plants.m-2) allocated to the main plot and sub plot, respectively. Water requirement for the medicinal plant under Mashhad climatic conditions was determined by using AGWAT equal to 2000 m3.ha-1. When the plants were yellow harvesting operation was performed. At first, five plants per plot were randomly selected for measurement of yield components. After removal of margins, to determine the seed yield, the remaining area was harvested. The studied criteria were number of flowers, flower yield, biological yield, seed yield, number of seed, 1000-seed weight and number of branches per plant of borage. To analyze the variance of the experimental data and drawing of diagrams, MSTAT-C 8 and Excel software was used. Means were compared according to Duncan multiple test at the 5% probability level. Results showed that simple and interaction effects of irrigation level and plant density were significant on flower yield, seed yield, biological yield, flower number, branch number and seed number of borage. One thousand-seed yield affected significantly by different irrigation levels. These morphological changes in growth can be considered as a morphological adaptation of the medicinal plant to water and environmental stresses to decrease transpiration and to induce a lower consumption of water. The growth is the most important process that is affected by water stress and the decrease in the growth of cells leads to decrease the plant height and number of branches. The highest and the lowest flower yield were observed in I3D3 and I1D1 with 0.81 and 0.14 g.m-2, respectively. The maximum and the minimum flower number, biological yield and seed yield were recorded in D3I3 (with 69.60 flowrs.m-2, 592.07 g.m-2 and 29.57 g.m-2) and D1I1 (with 3.89 flowrs.m-2, 134.42 g.m-2 and 3.36 g.m-2) respectively. According to the results obtained in the present study, the effects of irrigation levels and plant densities had significant effects on yield and yield components of borage. By increasing in irrigation level improved growth characteristics and yield, but by increasing in plat density up to 40 plants.m-2 declined its growth and yield due to inter species competition for water and nutrient absorption.
Acknowledgement
This research was funded by Vice Chancellor for Research of Ferdowsi University of Mashhad, which is hereby acknowledged

Weeds are one of the most important factors in reducing crop yield. Excessive use of herbicides for weed control because of the environmental pollution and ecological damaging effects does not have the necessary sustainability. One of the strategies to reduce the herbicides use in agriculture is use of intercropping systems with cover crops. Additive intercropping of different crop together through create an intense competition micro-ecosystem, provided the conditions that weeds damage would be minimized in these situations. This study was conducted to evaluate the quantitative usefulness of sweet corn-mungbean intercropping and its effect on weed control.
The experiment was conducted as factorial base on randomized complete block design with three replications. The first factor consisted of 6 levels of different cultivation systems (sweet corn and mungbean monoculture, intercropping of 20, 40, 60 and 80 percent of net density mungbeans with sweet corn) and the second factor was two levels of control and lack of weed control. Each plot had a length of 6 meters, including 4 rows by 60 cm distance. In monocultures, sweet corn (8.3 plant m-2 density) with 20 cm plant spacing and mungbean (8.23 plantm-2 density) with 7 cm plant spacing were planted. In intercropping treatments also sweet corn and mungbean were planted on both sides of the heap that plant spacing for sweet corn was 20 cm and for mungbean base on additive intercropping treatment were 8.7, 11.6, 17.5 and 35.8 cm respectively for creation of 80, 60, 40 and 20 percent of mungbean optimal density.
Weed competition reduced 1000 seed weight, seed number per row and canned grain yield of sweet corn by 13.8, 24 and 42.6 percent respectively. The highest (301.7 g) and lowest (281.8 g) of 1000 seed weight of sweet corn were related to intercropping of 20 and 80% optimal mungbean density with sweet corn, respectively. The highest (24.3) and lowest (20.6) of seed number per row of sweet corn were obtained respectively in intercropping of 40 and 80% optimal mungbean density with sweet corn. Compared to monoculture treatment the only intercropping treatments of 40 and 60% mungbean sweet corn increased the canned grain yield of sweet corn significantly.
Weeds competition and cultivation system had significant effect on 1000 seed weight, pod number per plant, seed number per pod, grain yield, biological yield and harvest index of mungbean. Treatments of 60% mungbean sweet corn intercropping and mungbean monoculture had the highest (40.8 g) and lowest (37.7 g) 1000 seed weight of mungbean respectively. Intercropping of sweet corn 20, 40 and 60% mungbean treatments increased number of pods per mungbean plant compared to pure culture significantly. In all of the intercropping treatments relative to mungbean monoculture the seed number per pod was increased. In the absence of weeds, intercropping of sweet corn 80% mungbean and in the presence of weeds, intercropping of sweet corn 60% and 80% mungbean had the similar mungbean grain yield (no significant difference) with the mungbean monoculture. Weed competition decreased the 1000 seed weight, pods number per plant and seed number per pod of mungbean about 13, 27 and 15 percent respectively. The highest weed dry weight (802.4 gr m-2) was observed in the pure culture of mungbean without non-significant differences with the sweet corn monoculture.
The lowest weed dry weight (465.9 gr m-2) was observed in the intercropping treatment of sweet corn 40% mungbean without non-significant differences with other intercropping treatments.
In all of the intercropping treatments the land equivalent ratio was greater than one (LER≥1) and ranged from 1.41to 1.89.
Based on the results of this experiment, additive intercropping sweet corn and mungbean in all of additive mungbean levels had the higher usefulness than monoculture of these species and in all of the intercropping treatments land equivalent ratio was more than one (LER≥1). The best additive intercropping treatment was sweet corn 40% mungbean.

IntroductionOil as a major source of food and energy has an important role in human nutrition. A great deal of Oil produced in Iran is originated in vegetable Oils. Oil-producing crops such as Canola play a significant role in oil production industry, and as a sole source of saturated fatty acids, has an important role in public health. . Rapeseed (Brassica napus), also known as oilseed rape and Canola, is a bright yellow flowering member of the family Brassicaceae, and is grown for the production of edible vegetable oils, biodiesel and animal feed, globally. The harvested area of Canola in Iran has had an increasing trend in the recent years and requires more agronomic researches to achieve the optimum yield of the oil-seed crop and meet the oil demands via increasing its oil yield and production. Optimum plant density per unit area is an important agronomic factor, which maximizes plant access to environmental growth sources during the growing season. This is an essential factor, which contributes to maximum plant yield. This factor varies in terms of region and depends on plant variety. Proper weed control and optimal weed management are another important factors in yield improvement. Weeds damage products both quantitatively and qualitatively. Qualitative damage reduces product's quality, nutritional value and toxicity (if weeds mix with the product excessively). Quantitative damage slightly reduces production per unit area. Laansite et al.(2008) reported that grain yield was significantly affected by increased plant density in Canola. They also showed that increased plant density reduced the number of tributaries per plant. The number of pods per unit area was the most important indicator that increased as plant density increased. The goal of this study is to investigate different agronomic and physiologic characteristics of Canola under different density and weed management levels in Zabol, Iran.
Materials and MethodsThe study is conducted in Dawlat Abad village located in south of Zabol (61° 29 E and 31° 2 N and 487 m above sea level) in 2012-2013 growing season. Two levels of weed managements as the main-plot factors and four levels of plant density as the sub-plot factors was performed based on a RCBD as split plot arrangement. The treatments were applied as: W1: weed control and W2: no weed control; D1: 50 plants per square meter, D2: 75 plants per square meter, D3: 100 plants per square meter and D4: 125 plants per square. In order to evaluate the effects of the treatments on the Canola, some agronomic indices like: plant height, number of tributaries per plant, number of pods per plant, thousand grain weights, dry matter yield, grain yield, weed biomass, oil content and yield, were measured at the end of the experiment.
Results and DiscussionThe results of this research showed that weed control had a significant effect on grain yield and oil yield of Canola. In addition, the density of 75 plants per square meter not only improved yield components, but also significantly increased grain yield and oil yield (oil content). However, the lowest weed biomass and the highest dry forage of canola were obtained at a density of 125 plants per square meter. This result recommended that properly weed control and cultivating 75 plants per square meter of canola can be the optimum treatment to obtain the highest grain yield and oil content in Zabol region. This is while densities with more than 75 plants per m2 are proper to control weeds and produce forage in Canola.
ConclusionOur result showed that increasing plant density increased canola yield and yield components and resulted in better weed control, allowing for the use of reduced herbicide rates in way to reach sustainable agriculture. In fact, the result revealed that manipulating plant density in canola production has potential to affect weeding and finally these two methods improved quantitative and qualitative characteristics of canola.

Low sustainability, soil erosion and loss of soil fertility in conventional systems are the major threats to the agricultural production systems. These threats leads researchers towards more attention to different agroforestry systems including alley cropping as a solution in different regions of the world. Agroforestry has attracted considerable attentions because of its potential to maintain or increase productivity in areas with high energy input in which large scale agricultural systems are impractical. It is often assumed that appropriate agroforestry systems can provide the essential ecological functions needed to ensure sustainability and maintain microclimatic and other favorable influences, and that such benefits may outweigh their enhanced use of water in areas of limited water availability. Evidences suggest that diversity in agroecosystems, in particular the integration of different perennial crops or trees (agroforestry), augments nutrient capture and cycling processes; processes that in turn lead to reduced reliance on nutrient or water inputs, abatement of air and water pollution, and enhancement of other ecosystem services across multiple spatial and temporal scales. Agroforestry is viewed as providing ecosystem services, has many environmental benefits and economic advantages as part of a multifunctional agroecosystem. Conventional cultivation of barley and wheat systems in Saman Region has many problems about sustainability of production, erosion of soil, yield stability and soil nutrient properties. On the other hand, planting of Almond is a good option for farmers to make orchards, in compare to Nut. Although some farmers do Agroforestry as an innovative practice, but studying the advantages of these systems and finding their rewards, because of its unique benefits in dry, poor and endangered areas, could help farmers to increase their cultivation area as they wish, particularly in Saman region.
In order to evaluate the benefits of a tree-based intercropping system, a study was conducted in an almond-based agroforestry plantation located in Saman region of Shahrekord, Iran (32˚43ꞌ N latitude and 50˚49ꞌ E longitude, with an altitude of 2085 m) based on a completely randomized design with four replications in 2014-2015.,The region is a semi-arid area receives 346 mm precipitation annually distributed only in 5-6 months.. Treatments include different types of cultivation systems: almond - wheat, almond - barley, and sole cropping of Wheat and Barley. Measured traits were leaf area index, plant height, spike length, dry matter, number of grains per spike, number of spikes per m², 1000 grain weight and grain yield (per unit area) and actual yield, biological yield and harvest index of wheat and barley.
Results showed that the highest yield (456 g.m-2) was acquired from almond-barley agroforestry system and the lowest from almond-wheat (233 g.m-2). Cultivation of barley in almond-barley system increased dry matter (14%) and grain yield (28%). Intercropping with almond tree increased leaf area Index, plant height, number of tillers, spike length and dry weight, especially for barley. So Agroforestry may increase morphological characteristics rather than the others. But number of spike, seed number and 1000 seed weight increased just for barley and decreased in wheat, However agroforestry increased biological yield in both barley and wheat, but the trend for grain yield was only in barley and some decrement were seen for wheat. It could be due to difference in filling period length and commence, and accordance with crucial developmental stage in almond.
Results of this study showed that the highest biological and grain yields were obtained from barley at agroforestry system with almond tree, indicating that barley is a more suitable option for multiple cropping compared to wheat. It may be due to higher dry matter accumulation of barley before bud developing and shading of almonds lead to higher dry matter accumulation, the situation that will occur for wheat latter. so barley- almond agroforestry system could be an effective technique to increase productivity and satisfying economical purposes in Saman region, Iran.

In order to evaluate the effect of different amounts of nitrogen fertilizer on oil and porotein content and nitrogen use efficiency of five sesame varieties under weed competition condition, this study was carried out at Omidieh (Boshehr province) during summer of 2013. Treatments were arranged in split factorial based on RCBD with three replications. The main plot consist of nitrogen fertilizer application levels as control, non application and application of 50 and 100 kg.ha-1 nitrogen from urea form and subplots were in a factorial combination of sesame varieties (Behbahan landrace, Yellow-white, tn-238 and tn-240) and weed competition (weed free and weed infest) . The results showed that the effect of nitrogen fertilizer on grain yield of different sesame varieties was significant. The highest grain yield (220 g.m-2) was obtained from Behbahan landrace with 100 kg.ha-1 nitrogen application under weed frees condition and the lowest was achieved from tn-238 and tn-240 lines without nitrogen application under weed infests condition. The highest oil percent (44%) was belonged to tn-238 line whitout nitrogen application and the lowest (35%) was achieved from Yellow-white variety with 100 kg.ha-1 nitrogen application. Also the highest oil yield (83 kg.ha-1) was belonged to Behbahan landrace with 100 kg.ha-1 nitrogen application under weed free condition. Increasing the nitrogen fertilizer application decreased nitrogen utility efficiency. The highest nitrogen utilisation efficiency achieved from Behbahan landrace in no nitrogen fertilizer application.

A pot experiment was carried out to investigate competition of wheat against wild mustard affected by salinity and N fertilizer levels، in Ramin Agriculture and Natural Resources University of Khouzestan greenhouses during 2012-2013. Experiment was Factorial in a completely randomized design in four replication. Experimental factors in trials was nitrogen levels (0، 60، 120 and 180 kg. ha-1 from Urea fertilizer sources) and irrigation water salinity (0، 3، 6 and 9 ds. m-1 by NaCl). Result show that the highest dry matter of wheat was obtained in 120 and 180 kg N. ha-1 without salinity. In the rate of 120 kg N. ha-1، there was no significant difference between salinity levels، in term of wheat dry matter. The lowest dry matter of wheat was observed in 9 ds. m-1 without nitrogen. Increase of nitrogen levels in saline conditions، caused to alleviate effect of salinity stress on wheat growth. However، further increase of N levels caused to decrease the competition ability of wheat against wild mustard and that failed to reduce the high levels of salinity reduces of wheat growth.

Proper application of herbicides is a major concern in sustainable agriculture. This issue depends on our knowledge about weed plants، especially weed-crop competition. Therefore، In order to evaluate the effect of weed competition on some dry bean’s traits an experiment was conducted in 2011. The experiment was a randomized complete block design with 3 replications. Treatments included weed-infested and weed-free periods until 0، 10، 20، 30، 40 and 50 days after crop emergence. In order to evaluate trends of dry bean’s traits Boltzmann model was fitted to the data. Crop height had a descending trend in weed-infested treatments، while it had an ascending trend in weed-free plots. Increase in duration of weed interference reduced main stem’s node formation of the crop. Weed interference affected crop’s number of branches. This trait had a descending trend in weed-infested plots، while it was ascending in weed-free treatments. Weed competition influenced pods length as well، so that the minimum value of this trait (6. 56 cm) was observed in full season weed-free treatment. Regression analysis revealed a significant negative relationship between weed biomass accumulation and evaluated dry bean’s traits (height، number of nodes in main stem، number of branches and pods length) at 1% probability level. Therefore، weeds are able to restrict dry bean’s development and growth through constraining environmental essential resources in which consequently lead to a final yield reduction.