جستجوی مقالات مرتبط با کلیدواژه "monoculture" در نشریات گروه "زراعت"

In order to evaluate yield and yield components in intercropping barley with vetch, a two-year field experiment was conducted at the Agricultural and Natural Resources Research Station of Miandoab. The arrangement consisted of 9 mixing treatments with densities of 200 Vetch plant + 300 Barley plant, 200 Vetch plant + 500 Barley plant, 200 Vetch plant + 700 Barley plant, 400 Vetch plant + 300 Barley plant, 400 Vetch plant + 500 Barley plant, 400 Vetch plant + 700 Barley plant, 600 Vetch plant + 300 Barley plant, 600 Vetch plant + 500 Barley and 600 Vetch plant + 700 Barley plant per square meter and sole culture of both crops. The experimental design was a randomized complete block design with four replications. The result showed The highest spikes per square meter, thousand kernel weight, biological yield, and grain yield in barley were observed in the sole culture of barley. Also, the highest plant height, number of seeds per plant, thousand kernel weight, biological yield, and grain yield in vetch belonged to the sole culture of vetch. However, the highest Land equivalent ratio (LER) belonged to treatments of 200 Vetch plants + 500 Barley plants by 1.49,

Intercropping is an ecological crop management method in which at least two plant species grow simultaneously on a field. Increased land productivity in intercropping of cereals and legumes is mainly due to the positive interaction between cereals and legumes in the rhizosphere, which increases the efficiency of soil resource utilization, especially nitrogen (N). Mixed cultivation of legumes with cereals provides higher land use efficiency, lower water consumption, and greater environmental benefits than cereal monocultures. Salicylic acid (SA) is a natural plant hormone that affects various physiological and biochemical functions in plants, because it can act as a regulatory and mediating signal in the plant's response to abiotic stresses such as drought. In recent years, nanotechnology has also been introduced into agriculture, and several benefits of nanoparticle applications such as nano-silica (nSiO2) have been reported that can be used to increase the supply of nutrients to agricultural products. The aim of this study was to determine the possible role of growth regulators of salicylic acid and nanosilica particles (nSiO2) on crop yield in maize and mung bean intercropping under drought stress conditions.

The experiment was conducted in 2019-2020 cropping year in the research farm of Agriculture and Natural Resources Campus, the University of Tehran, located in Karaj. The experiment was performed in the form of split- split plots based on a randomized complete block design with three replications. The main plot was drought stress at two levels of full irrigation and cessation of irrigation, the sub plots included different intercropping arrangements of maize and mung bean: (maize monoculture (C100), maize 80: mung bean 40 (C80:M40), maize 80: mung bean 60 (C80:M60), maize 50: mung bean 50 (C50:M50) and mung bean monoculture (M100) and the sub-sub plots were four treatments of silica nanoparticles +salicylic acid, silica nanoparticles, commercial salicylic acid and control. Statistical calculations were performed by SAS 9.2 and Excel software in this study. The mean comparison was performed by LSD test and the probability level was considered 95% in all analyzes.

The results showed that the highest maize grain yield was obtained in the monoculture treatment, Si + Sa combined fertilizer and full irrigation, which was 179% higher than the lowest treatment (C50:M50 intercropping, control and drought stress). The highest biological yield of maize was obtained in the complete irrigation and Si + Sa fertilizer treatment under monoculture conditions. The lowest value of this index was observed in the treatments of drought stress, control without fertilizer and C50:M50 intercropping conditions. The highest yield of mung bean seeds was obtained in monoculture of mung bean, application of Si + Sa fertilizer and complete irrigation. The highest biological yield belonged to mung bean monoculture treatment, nano Si + Sa compound fertilizer and complete irrigation. The lowest was obtained in C50:M50 and C80:M60 intercropping treatments, non- fertilizer application and drought stress. Also, the highest land equivalent ratio was obtained in full irrigation and C80M60 intercropping and nano Si + Sa fertilizer treatment (1.57).

general, the results of this study showed that, drought stress reduced all the studied traits. While intercropping with increasing diversity had a significant effect on important agronomic traits under both optimal irrigation and drought stress conditions. LER values were more than one in intercropping crops that indicated higher ground productivity in these planting patterns than in monoculture of crops. The highest LER value was obtained in C80:M60 intercropping treatment under non- stress and application of nano Si + Sa. Silica nanoparticles and salicylic acid fertilizers had a positive effect on grain and biological yield of both plants as well as land equivalent ratio and reduce the negative effects of drought stress on plants and can be used as suitable approach to achieve sustainable agriculture goals.

Intensive agriculture, despite high production, has adverse environmental effects, mainly due to the use of pesticides and chemical fertilizers. Therefore, we need alternative agricultural systems that are more economically and environmentally sustainable to produce crops. One of the sustainable methods in the production of agricultural products is intercropping. Intercropping of two or more species in a plot of land can increase biodiversity and resource utilization as agricultural perspective, which in turn can lead to increased yield stability. Intercropping uses resources more efficiently than monoculture, preventing the growth and spread of weeds by shading and suffocating weeds, and in some cases with allelopathic. Intercropping of cereals and legumes is recommended for the development of sustainable food production systems, especially in planting systems based on reduced consumption of foreign inputs. The importance of these systems depends on the nitrogen stabilized by the legumes. The aim of this experiment was to study the effects of row intercropping of barley and vetch and different levels of ammonium nitrate fertilizer on weed biomass, yield components and yield of two species in Karaj climatic condition.

This experiment was performed as a factorial split plot based on randomized complete block design in 2019-2020 cropping year in the research farm of the Agriculture and Natural Resources, University of Tehran. Main plots included three levels of ammonium nitrate fertilizer (0, 35 and 70 kg.ha-1) and sub-plots include different ratios of barley and vetch (100% barley, 80% barley: 20% vetch, 80% barley: 45% vetch, 80% barley: 70% vetch, 100% vetch, 80% vetch: 20% barley, 80% vetch: 45% barley, 80% vetch: 70% barley) weeding and non-weeding were in three replications. Plant density in sole barley and vetch were 250 plants per square meter. The method of cultivation in this study was additive intercropping. Seeds were sown on November 6th. The first stage of fertilization was done simultaneously with planting and one third was added to each plot and the second and third stages of fertilization were performed in two stages of stem emergence and spike emergence, respectively from ammonium nitrate fertilizer source. The final harvest was done on July 28th. Data were analyzed using SAS 9.1 software. The least significant difference test (P≤0.05) was used to compare the means.

The highest barley grain yield (432.44 g) was related to sole barley, 70 kg ammonium nitrate and weed control, which was not significantly different with 80% B: 45%V, 70 kg ammonium nitrate and weed control. Also, the highest yield of vetch grain (161.47 g) was obtained in sole vetch, application of 70 kg ammonium nitrate and weed control treatment, which was not significantly different with 80%V: 20%B intercropping, application of 70 kg ammonium nitrate and weed control treatment. Weeds in this experiment include: Wild oats (Avena fatua), ryegrass (Lolium temulentum), Bromus (Bromus tectorum), Fox tail (Alopecurus myosuroides), Wild mustard (Sinapis arvensis), Creeping Thistle (Cirsium arvense), London rocket (Sisymbrium irio), Cockspur grass (Echinochloa crus-galli) and Cornflower (Centaurea cyanus). The highest dry weight of weed (231.62 g) was observed in sole vetch, application of 70 kg.ha-1 ammonium nitrate fertilizer treatment. The highest land equivalent ratio LER (1.68) is related to 80% V: 70%B, non-application of ammonium nitrate fertilizer in weed control condition. Intercropping was successful in controlling weeds and using resources, thereby increasing the yield of plants in the experiment.

The results obtained from the experiment showed that all different systems of barley and vetch intercropping had land equivalent ratio higher than one, which indicates the superiority of intercropping over pure crops in the land use and crop production. Intercropping treatments were also able to control weeds. Intercropping with high ability to suppress weeds were able to use more resources. On the other hand, vetch biologically stabilized nitrogen was able to reduce the need for fertilizer in plants.

In order to investigate the effect of different sources of fertilizer and patterns of mixed cultivation of chicory (Cichorium intybus L.) and annual medic (Medicago scutellata) on agromorphological characteristics and forage yield a factorial experiment was carried out in a randomized complete block design with three replications .The first factor was different fertilizer sources (Chemical, Organic and Integrated (including; . Chemical fertilizer (urea + triple super phosphate) ,Vermicompost fertilizer and Combined fertilizer (50% chemical fertilizer + nitroxin biofertilizer + fertile phosphate 2) and the second factor was 5 levels of intercropping patterns including: pure cultivation of chicory, pure cultivation of annual medic, one row of chicory: one row of annual medic, One row of chicory: two rows of annual medic and two rows of chicory: one row of annual medic. Studied traits for chicory and medic were including: plant height, number of sub-branches, number of leaves per plant, chlorophyll index, leaf area index, dried forage yield and advantageous indices in intercropping including land equivalent ratio (LER), actual yield loss (AYL) and intercropping advantage (IA). The maximum dried yield of chicory and annual medic (4 and 4.6 ton.ha-1 ,respecyively) obtained in pure cultivation and chemical fertilizer source, which was not significantly different from pure cultivation and vermicompost and integrated fertilizer sources. Considering the total yield of two crops, and land equivalency ratio higher than one, the mixed ratios of chicory-medic with vermicompost and combined fertilizer sources were beneficial compared to sole cropping of each crops.

Wild oat is considered as one of the most problematic weeds in cereals due to compatibility with ecological conditions and competition. The emergence pattern of this weed allows its presence and competition with wheat throughout the growing season. To evaluate the effect of sowing time and depth on wheat and winter wild oat competition, a field experiment was conducted in a split-split plot designe with three replications in 2016-2017. Main plots were two sowing dates of wheat and wild oat (November 10 and December 15), subplots were six wild oat populations (Shiraz, Kurdistan, Mashhad, Kermanshah, Karaj and Ahvaz) and sub-sub-plot were seed sowing depth of wild oats (2 and 5 cm). The results showed that emergence rate of wheat was higher than wild oat populations in both sowing dates. In November sowing date treatment, wheat produced more individual weight in competition with wild oat. Competition with wild oat was effective on wheat height. Ahvaz population had the greatest (wheat height 74.16 cm) effect on reducing wheat height in November sowing date. In December sowing date, Karaj population had the least (wheat height 89.66 cm) effect on reducing wheat height. Depending on sowing date and the population of wild oat, seed depth had different effects, so that in November sowing date and 5 cm depth, wild oat biomass (205.212 g/m2) was less than December (379.294 g/m2). Also, Karaj and Ahvaz populations had the lowest seed number in competition with wheat. Generally, the sowing date and seed planting depth of wild oat populations were effective on emergence model and competitive ability of this weed with wheat. These results we can be used to plan for the application of weed management methods such as selection of tillage systems.

Application of intercropping systems is one of the ecological methods for controlling weeds due to maximization of soil cover and plant diversity. In order to study the effect of intercropping system of indigo (Indigofera tinctoria L.) and roselle (Hibiscus sabdariffa L.) on biodiversity, weeds population changes and plant yield an experiment was conducted based on randomized complete block design with three replications in the Research Farm of South Kerman Agricultural and Natural Resources Research and Education Center, Jiroft, Iran, during 2014-2015 growing season. Treatments were additive and replacement series of intercropping including: I100:H100, I100:H50, I50:H100, I50:H50 and monoculture of indigo and roselle. The results showed that the density and biomass of Amaranth, Cyprus and other weeds (Heliotropium europaeum L., Heliotropium europaeum L. and Portulaca oleracea L.) were significant by intercropping of indigo and roselle. Amaranth weed density in I100:H100, I50:H100 and I100:H50 were 57.44, 81.5 and 70.38%, respectively, lower than roselle monoculture. The highest of Cyprus weed density was in indigo and roselle monoculture and I50:H50 intercropping ratio. The density of other weeds in I50:H50, I50:H100, I100:H50 and I100:H100 ratio were 44.4, 48.2, 51.8 and 77.7 % lower than monoculture. Weed biomass in I100:H100, I10:H50 and I50:H100 ratio were decreased by 25.44, 23.38 and 15.98 % in comparison to monoculture, respectively. The highest yield of roselle (1114.2 kg/ha) and leaf dry weight (3016.7 kg/ha) of indigo was observed in I100: H100 ratio. The values of the land equivalent ratio (LER) in all of intercropping treatments were greater than unit and the highest LER belonged to H100: I100 treatment, indicating that intercropping system outperforms the monoculture in terms of crop productivity and hence weed control.

Using an effective management method can reduce weed contamination of main crop plants. To investigate the effect of cover crops on weed control and potato yield an experiment was conducted based on randomized complete block design with three replications at Research Field of University of Mohaghegh Ardabili in autumn of 2017 and spring of 2018. Experimental treatments consisted of oat (Avena sativa L.), white radish (Raphanus sativus L.) and double blend cultivation with 50% seed ratio and control treatment at 2017 (autumn) and subsequent potato planting in 2018 (spring). The results showed that the cover crops had a significant effect on lambsquarter (Chenopodium album L.), Amaranthus retroflexus L. and total weeds biomass in the main crop (potato) but not on other weeds (including Cirsium arvense L.). The highest biomass (466.1 g.m-2) among the cover crops and the lowest winter weeds biomass were related to white radish monoculture. The lowest weed biomass of amaranthus and total weeds biomass were obtained from white radish, and the lowest biomass of lambsquarter was obtained from white radish+oat. White radish was able to control 45.7% of total weed biomasses compared to control treatment. The highest yield and average tuber weight, marketable percentage and the lowest small potato tubers were obtained by white radish. White radish had the highest yield (3.74 kg.m-2), which increased potato yield by 46.3%, as compared to the control treatment. The highest number of potato tubers was obtained from oat as cover crop. Growing white radish along with oats also had the highest percentage of oversize tubers. In general, white radish can be a good choice to be used for winter cover crop before potato planting, either as a intercropping with Poaceae species or as a monoculture.

 Intercropping is cultivation of two or more crops in a land in a growing season that the important goal of this is optimal use of growth resources and labors. The most important advanteges of intercropping is higher yield in a certain land by using the various traits such as canopy structure, the ability of root development, height, nutritional needs and efficient use of growth resources. The studies show that the responses of plant species were different in intercropping and monoculture cropping systems. The present research aimed to investigate the planting pattern and different levels of manure on competitive power and agronomic traits of garlic and spinach. This experiment was conducted as split plot based on completely randomized block design with three replications at the Agricultural Research Station, Ferdowsi University of Mashhad, during growing season of 2011-2012. The treatments were manure rates at three levels (0, 10 and 20 ton.ha-1) in main plots and 6 cropping systems (garlic and spinach monocultures and garlic-spinach intercropping with 1:1, 2:2, 3:3 and 4:4 ratio) in sub plots. Studied traits were included in height, fresh and dry weight of spinach and garlic, Land Equivalent Ratio, Aggressivity Coefficient and Competition Ratio. The results indicated that with increasing manure level to 20 ton per hectare, spinach fresh weight increased, significantly but this trend wasn’t observed in spinach dry weight. Also with changing cropping pattern, dry and fresh weight of spinach was affected, significantly. The highest dry and fresh weight of spinach was observed in garlic and spinach intercropping with 4:4 ratio. The investigation of interaction effect of planting pattern and manure showed that the highest fresh and dry weight of spinach were obtained in garlic and spinach intercropping with 1:1 and 4:4 ratio under 20 ton per hectare manure, respectively. The lowest spinach dry weight was in garlic and spinach intercropping with 3:3 ratio under 20 ton per hectare manure. Garlic dry and fresh weight wasn’t affected by manure rates, but cropping pattern affected dry and fresh weight of garlic, significantly. The highest fresh and dry weight of garlic was obtained in garlic monoculture without manure.In studied intercropping systems, land equivalent ratio (LER) was more of one. The highest LER was obtained in intercropping with 3:3 ratio without manure Conclusions In general, the best treatment for Aggressivity Coefficient, Competition Ratio and Land Equivalent Ratio was obtained in garlic and spinach intercropping with 1:1 ratio and 20 ton per hectare manure.

Plant growth involves a series of biochemical and physiological processes that interact with each other and environmental factors such as light. Evaluation of growth indices is important in analysis of factors affecting dry matter accumulation. Since more than one species grow in various farming systems such as alley cropping, so the behavior of crop next to each other could be very important. So the purpose of this study was to investigate the integration of trees and crop plants cultivated in alley-cropping System in order to maintain or even increase crop dry matter along with more efficiency of resources. It seems that multiple cropping can lead to a sustainable increase in agricultural ecosystems.
In order to evaluation of growth indices and physiological traits of wheat and barley in different cropping systems, a randomized complete block design was conducted with four replication in 2015 at Saman region. Treatments were included: 4 different cultural systems (Alley cropping of wheat and barley with almond and sole cropping of them. Leaf area index, dry matter accumulation, chlorophyll (a, b and total), proline, protein content and growth indices were measured.
Data showed that proline content, light absorption, crop growth rate (
CGR), net assimilation rate and relative growth rate were higher in barley – almonds system. The highest dry matter accumulation per unit area (1424 g/m2) also was obtained for barley – almonds system, while for the cultivation of wheat it's corresponding to 934 grams per square meter, had no significant difference with its sole cropping. The lowest rates also found for sole cropping of barley equal to 700 grams per square meter. It seems that barley less influenced with shading and competition for nutrients in this cultural system, so its dry matter accumulation will be greater compare to sole cropping and also to sole and intercropping of wheat. Highest light absorbance values obtained in this system too.
Alley-cropping in Chahar Mahal and Bakhtiyari province, especially in Saman as an organized cultivation system could notice as an effective way to increase productivity, land use and economic efficiency for trees and plants, such as barley. Therefore it may promote sustainable development of natural resources and the use of modern multiple cropping practices and utilization of space used per unit of time. Barley is the best option for cultivation under almond trees among conventional cereals in the region, because of the highest dry matter in this system. Wheat cultivation in these systems although did not change dry matter accumulation, but may increase land use efficiency and productivity. So barely gain more advantages in these conditions and is more suitable option for almond trees understory.

The study of weed flora changes under different crop management system is an important key to achieve successful weed management in every agroecosystem. This study was conducted in order to evaluate the effect of potato monoculture continuing on weed density and diversity in the conventional agroecosystems of Jiroft region-at 2015-16 in University of Jiroft, Iran. Agroecosystems, which was assessed in this study, were potato monoculture systems included continues monoculture period less than 3 years (S1), 3-6 years (S2), 6-9 years (S3) and more than 9 years (S4) and long-term fallow (F). Sampling was performed using systematic-randomized method in three stages (before sowing, 60 days after planting and 30 days after harvest) with 1×1 m2plot. Base on results 28 weed species were observed which 17 species of them were common in all five agroecosystems. ANOVA's result showed there were significant effect of continuing in potato monoculture on density weeds as Cyperus rotendus L., Cyperus esculentus L., Trifolium repens L., Chenopodium album L., Cynodon doctylon L., Amamrantus retrofloxios L. and Digitaria sanguilanis L. Increase of potato monoculture period from 3years in agroecosystem of S1 up to 9years in S4 agroecosystem caused to significant increasing in weed density so maximum weed density was observed in S4. Evaluating of diversity indices showed continuing in potato monoculture period had significant effect on diversity indices includes of Simpson, Shannon, Margalef, Menhinik and Evenness, so highest value of these indices (Simpson:0.97, Shannon: 3.65, Margalef: 5.24, Menhinik: 2.99) and lowest value (Simpson:0.87, Shannon: 2.22, Margalef: 3.88, Menhinik: 2.00) were observed respectively in agroecosystems of S4 and F. In summary continuing in period of potato monoculture caused to significant increase in weed flora density and diversity indices.

This research was carried out in order to evaluate weeds control with the sesbania and millet intercropping system in Agricultural Research Field, in University of Jiroft during 2014-2015. So this experiment was performed based on randomized complete block design with three replications and different replacement series of millet and sesbania intercropping which consist of 75:25 (M75:S25), 67:33 (M67:S33), 50:50 (M50:S50), 33:67 (M33:S67), 25:75 (M25:S75), and their monocultures. The results showed that different intercropping ratio had significant effect on total dry weight of weeds, total dry forage yield, forage yield of millet and sesbania. The lowest dry weight of weeds includes of Centaurea cyanus L., Salsola kali L. and Heliotropium spp, were observed in 75: 25(M75:S25). Increasing sesbania ratio of intercropping systems caused to incrementing dry weight of weeds, so the highest dry weight of weeds was observed in sesbania monoculture. Decreasing of total weeds dry weight in M75:S25, M67:S33, M50:S50, M33:S67, M25:S75, compared to sesbania monoculture was respectively 94.07%, 85.8%, 81.4%, 71.2% and 29.4%. The highest dry forage yield of common millet (11437kg/ha) and sesbania (1680kg/ha) obtained from monoculture. The LER for almost all intercropping treatments was significantly higher than monocultures which show, intercropping had advantage over monoculture in this research. The result indicated that intercropping could be advantageous in terms of weed controls and total yield performance in the sesbania and millet intercropping system.

A growing interest to use multiple cropping was due to potential of these planting patterns for increasing yield by improved resource use efficiency such as radiation use efficiency (RUE). In order to investigate the effects of plant diversity and nutrient resource on radiation use efficiency, an experiment was conducted as split plot based on complete randomized block design with three replications at the Agricultural Research Station, Ferdowsi University of Mashhad, Iran, during 2006 and 2007. Treatments included manure and chemical fertilizers as main plots and intercropping of 3 soybean varieties (Wiliams, Sahar and Gorgan3), intercropping of 3 Millet species (common millet, foxtail millet and pearl millet), intercropping of millet, soybean, sesame (Sesamum indicum) and intercropping of millet, sesame, fenugreek (Trigonella foenum-graecum), ajowan (Trachyspermum ammi) as sub plots. Results indicated that in the manure and chemical fertilizer treatments, LAI of plants in intercropping decreased compared to monoculture. The effect of planting pattern on RUE was significant. In monocultures, common millet and soybean (Wiliams and Gorgan3 varieties) had highest RUE based on photosynthetic active radiation (PAR). The lowest RUE was obtained in sesame and foxtail millet monocultures. In the intercropping systems, when functional diversity increased, radiation use efficiency was increased, so that maximum of RUE (3.31 g.MJ-1) was obtained in 4 species intercropping (common millet, sesame, fenugreek and ajowan). Minimum of RUE (1.96 g.MJ-1) was observed in intercropping of 3 millet species. The interaction of planting pattern and nutrient resource on RUE was significant. In general, the highest RUE was observed in 4 species intercropping (common millet, sesame, fenugreek and ajowan) with manure treatment.

To study the effects of intercropping on performance and quality of alfalfa and sainfoin, a field experiment as split plot in time arrangements in randomized complete block design with three replications was carried out at Research Farm of College of Agriculture, University of Tehran, Karaj, Iran in 2008-2009 and 2009-2010. Experimental treatments included: Monoculture of alfalfa, monoculture of sainfoin, 50% alfalfa+ 50% sainfoin as one alternate, 50% alfalfa+ 50% sainfoin as two alternates, 75% alfalfa+ 25% sainfoin, 25% alfalfa+ 75% sainfoin, 10% sainfoin+ 100% alfalfa,, 20% sainfoin+ 100% alfalfa, 30% sainfoin+ 100% alfalfa. Results showed that the effect of year and intercropping treatments on forage dry yield was significant. The highest dry yield (5011 kg.ha-1) was obtainedin 30% sainfoin+ 100% alfalfa and the lowest dry yield 3989 kg.ha-1) obtained in monoculture of sainfoin. The effect of intercropping on CP, DMD, ADF, ASH and CF was significant. Also, the effect of year on ADF and interaction effect of year × intercropping on DMD was significant. The highest CP (24%), ADF (29%), Ash (7.3%) and CF (32.2%) were obtained from monoculture of alfalfa, but the highest DMD (90%) was related to monoculture of sainfoin. In both years, the highest LER (1.26 and 1.28 for first and second years, respectively) were related to 30% sainfoin+ 100% alfalfa. Therefore, 30% sainfoin+ 100% alfalfa was identified as the best treatment of this experiment.

Improvement of resource use efficiency is a basic approach for sustainable agriculture. Applying intercropping systems, in which resources such as water, radiation and nutrients are used optimally, is one of these strategies. In order to evaluate radiation absorption and use efficiency in additive intercropping of maize-bean, an experiment was carried out in 2010, based on completely randomized blocks design with three replications, at Research Farm of Zanjan University. Treatments included different ratios of additive intercropping system (sowing 20, 40, 60 and 80% of common bean optimum density + optimum density of maize) and monoculture of these crops. Dry matter and leaf area of both crops were measured during the growth period. Results showed that the absorbed radiation by canopy of maize-bean intercropping in all treatments was higher than the monoculture of maize and bean, because the surface of canopy increases to absorb radiation. for intercropping system and result in more absorption of radiation compared to monoculture. The values of LERPAR were more than 1 in all intercropping treatments, which indicates the advantage of intercropping cultivation in comparison with monoculture system based on radiation absorption. Higher values of radiation use efficiency for maize and bean under intercropping system in comparison with monoculture of these crops confirmed the optimum use of radiation resource in intercropping system. Regarding the efficiency of radiation absorption by different intercropping treatments, the additive cultivation of 60% bean with 100% maize was identified as the best cropping pattern.

Barnyardgrass has always been considered as the most important weed of rice all over the world. Meanwhile, establishment of new species of this genus which is more adaptable to paddy ecosystem will increase the importance of this genus as a new threat to rice. In order to evaluate the competition of two species of barnyardgrass with rice, an experiment was conducted at Rice Research Institute of Iran (Rasht) in 2007. The experimental design was a randomized complete block with three replications arranged in a partial additive series. The treatments included two barnyardgrass species (E. crus-galli and E. oryzoides), and species density at four levels (0, 10, 20 and 40 plant.m-2), transplanted with Hashemi land races cultivar rice in local normal density (20 bunches.m-2) and each bunch included three seedlings. Destructive samples were taken two weeks after transplanting up to harvesting, that is, 5 times by 10 days interval in 0.25 m-2. Rice total dry matter accumulation (TDM), Leaf area index (LAI), crop growth rate (CGR), relative growth rate (RGR), yield and yield components were measured. Results showed that yield, yield components and growth indices were affected by both weed species significantly and no interaction between species occurred. Fitting the hyperbolic yield loss model to rice grain yield in barnyardgrass density showed that two weed species were not significantly different. Morphological similarity and ecological adaptability of new barnyardgrass species including resistance to flooding and also high similarity to crop plant that makes its hand weeding less efficient, implies E. oryzoides as a new threat for rice cultivation in northern paddy field of Iran. More investigation on biology of this species is suggested in order to present an applied integrated method for E. oryzoides management.