جستجوی مقالات مرتبط با کلیدواژه « غالبیت » در نشریات گروه « اکولوژی »

Awareness of biodiversity status is one of the requirements for adopting a conservation approach in rangelands ecosystems. In this regard, the present research was conducted in order to investigate the effect of slope direction on the values of plant diversity indices in the Astraglaus shrubland of Nazluchai region in 2017. For this purpose, in total, with the use of 230 sample plots of one square meter, which were placed at a distance of five meters from each other, along 50-meter transects; the crown cover percentage of plant species were collected in each of the main directions of the range (eight northern directions, five southern directions, five eastern directions and five western directions). Then, with the PAST software, the most important and widely used indicators of species diversity (Margalef, Taxa, Menhinick and Berger-Parker as species richness indices, Dominance, evenness, Simpson and Pielo as species evenness indices, Shannon and Brillouin as heterogeneity indicators) were calculated. Finally, using the one-way analysis of variance method, statistical comparison of the averages was carried out. The results showed; A total of 41 plant species were identified in the studied areas, and Margalef, Taxa, Shannon, Brillouin and Fisher's Alpha indices had a significant difference at the five percent level in different geographical directions. So that the highest value of these indices was related to the western direction, respectively 2.55, 12.2, 2.1, 1.88 and 4.05. Simpson's, Menhenik's, Dominance, evenness, Pielo and Berger-Parker indices were also not significantly different from each other in different directions. Although the two western and southern aspects were significantly different from each other regarding most of the indicators, nevertheless, the clustering results of the plant composition of the sites classified these two domains in one cluster with high similarity rate (around 70%). This finding indicates that the diversity indices are not able to provide information about the plant composition and should pay attention to the plant composition when using these indices. Finally, it should be mentioned that although Margalef, Taxa, Shannon, Brillouin and Fisher's alpha indices were able to separate the sites, but the proposal of using these indices in the monitoring plans of rangleands with the dominance of Astragulus microcephalus species in the northwest of the country, requires another researches.

  Intercropping, the agricultural practice of cultivating two or more crops in the same space at the same time, is an old and commonly used cropping practice which aims to match efficiently crop demands to the available growth resources. Intercropping of chickpea with linseed reduced the chickpea yield by 60.3%, although linseed occupied only 33% of the total area. The loss of chickpea yield was compensated by the additional yield of linseed, and thus the system productivity of chickpea + linseed intercropping was increased by 43.4% compared to the sole chickpea. Of this increase in system productivity, 65.3 and 34.7% were contributed by higher seed yield and higher minimum support prices of linseed, respectively, as compared to chickpea. The objectives of the present study were to study the competition indices of Pea and Lettuce intercropping, such as land equivalent ratio, relative crowding coefficient, aggressivity, pea equivalent yield and effects of nitrogen and different intercropping arrangements on the yield of sole pea, sole lettuce and intercropping yield of two plants. In order to study the effect of planting pattern and nitrogen application on yield and competitive indicators of pea and lettuce, a factorial experiment based on Randomized Complete Block Design was conducted with three replications at research farm of Gonbad Kavous University during the growing season of 2014-2015. The treatments of the planting pattern were included 9 levels of sole pea, 67% pea + 33% lettuce, 50% pea + 50% lettuce, 33% pea + 67% lettuce, 100% pea + 33% lettuce, 100% pea + 50 % lettuce, 100% pea + 67% lettuce, 100% pea + 100% lettuce and sole lettuce and the nitrogen factor was included three levels of non-application and application of 25 and 50 kg N.ha-1. Row spacing was 30cm. Density of pea and lettuce was 33.3 and 16.7 plants.m-2, respectively. The results showed that the effect of planting pattern and nitrogen application on the yield was significant on the confidence level of 99%. Additive treatment of 100% lettuce + 100% pea and lettuce sole cropping with 61565 and 61473 kg.ha-1 were produced the maximum yields and pea sole cropping with 11759 kg.ha-1 produced the minimum yield. Total yield was increased with increasing nitrogen fertilizer application. The maximum and minimum equivalent yield was achieved in additive treatment of 100% lettuce + 100% pea and sole cropping of pea, respectively. The most and the least pea equivalent yield were obtained from treatments of 50 kg nitrogen/ha and non-application of nitrogen with 20669 and 16689 kg.ha-1, respectively. Land equivalent ratio in intercropping treatments was greater than sole cropping. The maximum land equivalent ratio with 1.48 belonged to additive intercropping of 100% pea + 100% lettuce. Therefore, intercropping of pea and lettuce, especially in additive series was appropriate. Relative crowding coefficient in all traits was more than 1. Aggressivity index showed that pea in additive treatments and replacement of 33% lettuce instead of pea was the dominant plant. Increasing of actual yield was observed in all treatments, especially in additive series. Intercropping advantage and system productivity index in all treatments of additive and replacement treatments was greater than 1, therefore Intercropping had sufficient economic benefits in this mixture. Of the two plants of pea and lettuce, lettuce produced more yield than pea in all treatments. Additive treatment of 100% lettuce to pea and lettuce sole crop with 61565 and 61473 kg.ha-1 produced the maximum yield and pea sole crop with 11759 kg.ha-1 produced the minimum total yield. With increasing of nitrogen fertilizer consumption, yield was increased. According to the results, it seems that obtaining the maximum yield in the intercropping system required increasing plant density

In order to evaluate of peppermint and faba bean intercropping, a field experiment was carried out as a randomized complete blocks design (RCBD) with eight treatment and three replication at the faculty of Agriculture, University of Maragheh during 2015 growing season. Treatments were included sole planting of peppermint and faba bean, 1 row peppermint 1 row faba bean, 1 row peppermint 2 rows faba bean, 2 rows peppermint 1 row faba bean, 2 rows peppermint 3 rows faba bean, 3 rows peppermint 2 rows faba bean, 1 row peppermint 3 rows bean and 3 rows peppermint 1 row bean. Intercropping different patterns were calculated by means of land equivalent ratio (LER), standard land equivalent ratio (LERS), area time equivalent ratio (ATER), area harvest equivalent ratio (AHER), land use efficiency (LUE), peppermint equivalent yield (EYP), relative crowding coefficient (RCC or K), aggressivity (A), competitive ratio (CR), actual yield loss (AYL), monetary advantage index (MAI), intercropping advantage (IA), system productivity index (SPI) and relative value total (RVT). Results showed that seed yield of faba bean per occupied unit area and per intercropped unit area were affected significantly by intercropping patterns. The highest seed yield of faba bean per occupied unit was obtained in the 2:3 and 1:3 treatments. In addition, the highest seed yield of faba bean per intercropped unit area observed in faba bean sole crop. The highest values of LER, LERS, ATER, AHER, LUE, EYP, IA, MAI and SPI obtained in 2:3, 3:2 and 1:3 intercropping patterns, indicating that the intercropping systems were the most profitable on basis of agronomical and economical. Generally, the A, CR and AYL values in peppermint were higher than bean, indicating that peppermint was more competitive and dominant than faba bean. Generalley, in basis of more agronomy and economic indices in 2:3 cropping pattern, this cropping pattern was superier than other treatments.

Intercropping, the agricultural practice of cultivating two or more crops in the same space at the same time, is an old and commonly used cropping practice which aims to match efficiently crop demands to the available growth resources (Agegnehu et al., 2006; Dhima et al., 2007). Intercropping of chickpea with linseed reduced the chickpea yield by 60.3%, although linseed occupied only 33% of the total area. The loss of chickpea yield was compensated by the additional yield of linseed, and thus the system productivity of chickpea linseed intercropping was increased by 43.4% compared with sole chickpea (Ahlawat & Gangaiah, 2010).
The objectives of the present study were to study the competition indices of barley and pea intercropping and effects of nitrogen and different intercropping arrangements on forage yield.
In order to evaluate effects of nitrogen and different intercropping arrangements of barley and pea on yield and competitive indices, an experiment was conducted as factorial based on Randomized Complete Block Design with three replications on farm research on Gonbad Kavous University (37°26’N, 55°21’E, and 45m above sea level) in 2011-2012. Different intercropping arrangement levels were a sole crop of barley, intercropping of one line barley and one line pea, intercropping of two lines of barley and two lines of pea, intercropping of three lines of barley and three lines of pea and sole crop of pea and nitrogen consumption was in four levels of none application of nitrogen and application of 25, 50 and 75 kg.ha-1.
Seed planting was done during the first week of December 2011. Sowing was performed manually by planting twice more seeds of pea than the expected plant density. Sole barley (cv. Sahra) planted at the rate of 160 kg.ha-1 and sole pea (cv. Sungro) planted at the rate of 500000 plants.ha-1. Row spacing was 20 cm. The experimental plots for a sole crop of barley, a sole crop of pea and one row of barley one row of pea were 4 rows and for two rows of barley two rows of pea and three rows of barley three rows of pea were 6 and 8 rows, respectively.
50% of urea was applied during sowing. The other 50% of urea was side banded when the barley plants were at flowering stage. Weed control was performed manually. Forage yield was determined by harvesting each crop from 2, 4 and 6 rows. Barley was harvested at soft drought and the pea was harvested at seed filling stage in 3 May 2012. Data were analyzed using SAS software. Analysis of variance was performed for the forage yield and Equal Yield of barley.
The results showed the effects of different intercropping arrangements, nitrogen application and interaction of different intercropping arrangements × nitrogen application on forage yield and Equivalent Yield of barley was significant (α= 1%). The high forage yield and Equivalent Yield of barley belonged to a sole crop of barley with application of 75 and 50 kg Nha-1 with 14.51 and 14.3 tonha-1, respectively. The minimum dry weight and Equivalent Yield of barley was obtained from the sole crop of pea without consumption of nitrogen with 3.76 and 4.7 tha-1, respectively. Increasing the pea and barley rows in intercropping treatments decreased forage yield because of lower yield of pea. Land Equivalent Ratio in intercropping treatments was less than 1. This index in barley was greater than pea (0.643, 0.588 and 0.543 for barley and 0.198, 0.247 and 0.362 for pea in 1, 2 and 3 rows, respectively). Other indices (Relative Crowding Coefficient, Aggressivity, Competitive Ratio, Actual Yield addition, Intercropping Advantage and Equivalent Yield of barley) in barley were also greater than pea in intercropping. Barley was the dominant crop in this study.
Forage dry weight and Equivalent Yield of barley in a sole crop of barley with consumption of 75 and 50 kgN.ha-1 was the maximum and in sole crop of pea with non-consumption of N was minimum. All indices in barley in this study were greater than pea. This indicated that barley was the dominant crop.

In order to evaluate the intercropping of corn (Zea mays L.) and bean cultivars (Phaseolus spp.) an experiment was carried out in a randomized complete block design with three replicaties at Sari Agricultural Sciences and Natural Resources University during growing season of 2010. The experimental treatments consisted of sole cropping of corn، white bean، bush bean، red bean، pinto bean and sword bean and 50:50 ratio of corn and bean types. In this experiment، the corn-bush bean and corn-pinto bean intercropping had the highest seed yield (5734. 4 and 5674. 3 kg/ha-1، respectively) and land equivalent ratio (LER=1. 13 and 1. 21، respectively). Evaluated intercropping indices indicated that red bean (k= 1. 85)، pinto bean (k= 2. 41) and sword bean (k= 2. 80) had the highest crowding coefficient whereas the maximum aggressivity value was belonged to pinto bean intercropped with corn (A= -0. 02). Also، both the red bean and pinto bean (CR=0. 75 and CR=0. 98، respectively) had the maximum competitive ratio. Furthermore، the most corn crowding coefficient (K=1. 15) was belonged to corn and sword bean intercropping and maximum corn aggressivity value was observed in corn intercropped with white bean (A=+0. 60) and bush bean (A=+0. 69). In conclusion، according to competition indices، intercropping of 50% corn + 50 % red bean and pinto bean plants were superior as compared to other combinations. Also، both the red bean and pinto bean (CR=0. 75 and CR=0. 98، respectively) had the maximum competitive ratio. Furthermore، the most corn crowding coefficient (K=1. 15) was belonged to corn and sword bean intercropping and maximum corn aggressivity value was observed in corn intercropped with white bean (A=+0. 60) and bush bean (A=+0. 69). In conclusion، according to competition indices، intercropping of 50% corn + 50 % red bean and pinto bean plants were superior as compared to other combinations.

The experiment was conducted in order to evaluate of competitive and economic indices in canola and pea intercropping at different rates of nitrogen fertilizer at Shahrekord University research farm during 1390 - 1391. Intercropping and sole cropping treatments (100% canola; 66% canola + 33% pea، 50% canola + 50% pea; 33% canola + 66% pea; 100% pea) were evaluated as the first factor and nitrogen rates (100% need; 75% need and 50% need) as the second factor in a randomized complete block design with three replications. The calculated competitive indices were included land equivalent ratio (LER)، relative crowding coefficient (K)، aggressively (A)، the system production index (SPI)، actual yield loss (AYL)، competitive ratio (CR) and economy indices included monetary advantage index (MAI)، and the intercropping advantage (IA). Results showed that all the competitive and economic indices had the highest amount in 50 and 75% of nitrogen requirement. The amounts of AYLt and SPI and economic indices (MAI and IA) were positive for all intercropping ratios. Also، LERt and Kt for all intercropping ratio were greater than one، that indicating the superiority of intercropping over sole cropping any of the two plants. The positive values aggressively index and the greater than one values competitive ratio for canola، indicated canola was superior competitor in compared to pea. In conclusion، the evaluation of competitive and economic indices appropriately describes intercropping advantage of canola with pea in reduced nitrogen fertilizer conditions.

In order to study the different levels of irrigation on diversity، density and compound of weed species in corn field، experiment was conducted at Agricultural Research Station، Ferdowsi University of Mashhad during growing season of 2008-2009. The experiment was with four levels of irrigation (6130، 7290، 8800 and 12330 m3) and four levels of weed control (complete control، broad-leaves control، grasses control and without control). Weed sampling was done at four stages including first، meddle and end of critical period weed control and harvest then all species counted species separate. The results showed that in different levels of irrigation the weed species were different. At the first time of critical period، the most diversity was in 8800 and 7290 m3 and the minimum diversity was in 12330 and 6130 m3 irrigation levels. At the harvest time، the most diversity was in 12330 and 6130 and 8800 m3 irrigation levels and least diversity within different indexes were in 7290، 8800 and 6130 m3 irrigation levels، respectively. Stability index changed at different levels of irrigation. In addition، maximum when the irrigation level was in minimum level، however، highest level of irrigation caused the maximum unstability of species but levels of irrigation had no significant on dominance index.

The present study was conducted to quantify the density and abundance of weeds in wheat fields of South Khorasan province during 2010 and 56 species of weed form 16 plant families were identified in 240 farms of eight towns around this province. The most families in number of species were pertaining to Poaceae، Asteraceae and Chenopodiaceae with 15 (26. 79%)، nine (16. 7%)، six (10. 71%) and six (10. 71%) species، respectively. The most frequencies were related to yarrow (Achilla biberstinii L.) by 37. 38% from the Asteraceae family، hoary cress (Cardaria draba L. (form Bressicaseae family by 28. 3% and common lambsquarters (Chenopodium album L.) from Chenopodiaseae family by 37. 47%. Hoary cress، common lambs quarters، bermuda grass (Cynodon dactylon L.)، camelthorn and prostrate knotweed (Polygonum aviculare L.) were allocated the highest average density of the weeds with 1. 38، 1. 31، 1. 29، 1. 27 and 1. 04 plant. m-2، respectively. The most abundant of weeds were camelthorn، common lambsquarters and yarrow. The highest and the lowest diversity were related to Qaen city with 29 species and Birjand City with 13 Species، respectively.

The mathematical formulas for evaluation of intercropping advantage provides accurately assess of intercropping systems based on economic and competitive parameters. In order to study the economic and competitive indices on intercropping of soybean with sweet basil (Ocimum basilicum L.) and borage (Borago officianalis L.) an experiment was performed in a randomized complete block design with 9 treatments and 3 replications in 2011 at a field located 10 km of Shirvan (Northern Khorasan). Treatments were included different ratios of intercropping of soybean with sweet basil and borage (100:0، 75:25، 50:50، 25:75، and 0:100، soybean: sweet basil or borage). In this experiment، we used the indices of land equivalent ratio (LER)، relative crowding coefficient (K)، aggressivity (A)، competitive ratio (CR)، system productivity index (SPI)، actual yield loss (AYL)، area-time equivalent ratio (ATER) and competitive index (CI) and economic indices of monetary advantage (MAI) and intercropping advantage (IA). The results showed that intercropping had superiority compared to monoculture. In all ratios، aggressivity indices indicated that soybean was dominant compared to sweet basil and borage. The results suggested that there was a relationship between economic and competitive indices، so that economic advantageous was observed in treatments with LER and K higher than one. In general، treatments of 75% soybean: 25% sweet basil and 50% soybean: 50% borage were superior than other treatments. The indices indicated that intercropping soybean with sweet basil has a high efficiency when compared to intercropping soybean with borage.