بررسی عملکرد، اجزای‌ عملکرد و شاخص‌های مختلف ارزیابی در کشت مخلوط درهم و ردیفی کنجد (Sesamum indicum) و لوبیا (.Phaseolus vulgaris L)

Introduction
Intercropping as a common method in sustainable agricultural systems, plays an important role in increasing productivity and yield stability to improve utilization of resources )Alizadeh et al., 2010). Studies in different countries showed that intercropping causes increase in diversity, production and more efficient use of water resources, land, labor and nutrients and also reduces problems caused by pests, diseases and weeds (Awal et al., 2006) and improves environmental conditions for plant growth )Alizadeh et al., 2010). One the most important benefits of intercropping is increasing production per unit area compared with sole cropping (Banik et al., 2006(.The reason for increasing the yield in the intercropping is the better use of environmental factors such as water, nutrient and light )Alizadeh et al., 2010). TohidiNejad et al, (2004) evaluated the intercropping of corn (Zeamayz) and sunflower (Helianthus annuus( and reported that intercropping, due to more efficient use of light, improved the yield of both plants. Pouramir et al, (2010) investigated the intercropping of sesame (Sesamum indicum L.) and chickpea (Cicer arietinum) and concluded that yield of chickpea was significantly affected by intercropping with sesame and the highest yield of chickpea was obtained in monoculture. Beheshti (Beheshti et al., 2010) evaluated the intercropping of sorghum (Sorghum bicolor) and soybean (Glaycin max) and stated that in all the intercropping treatments, land equivalent ratio was increased. The present study was designed to investigate the effects of mixed and row intercropping on yield of sesame (Sesamum indicum L.) and bean (Phaseolus vulgaris L.).
Matrials and Methods
In order to study the effects of mixed and row intercropping of sesame and bean on yield and yield components in two species of sesame and bean, a split-plot experiment based on randomized complete blocks design with three replicates was performed in research farm of Ferdowsi University of Mashhad in 2011-2012. Cropping pattern (mixed or row intercropping) was allocated to the main plots and different planting ratios (25% bean +75% sesame, 25% sesame +75% bean, 50% sesame +50% bean, sole cropping of sesame, sole cropping of bean) were assigned to the sub-plots. Density of planting for sesame and beans were 40 and 20 plants per square meters respectively.
Crop combination in row intercropping was as follows:
75% sesame + 25% bean: planting three rows of sesame and one row of bean.
25% sesame + 75% bean: planting three rows of bean and one row of sesame.
50% sesame and 50% bean: planting two rows of sesame and two rows of beans.
Indices such as Land Equivalent Ratio (LER), Aggressively index (AG) and Relative Crowding Coefficient index (RCC) were used (Vandermeer, 1989). For analyzing data, SAS ver.9.1 was used and mean comparison was performed based on Duncan test and for drawing charts Excel was used.
Results and Discussion
Results indicated that yield and yield components of sesame and bean were affected by different treatments. In all cases, row intercropping showed superior compared with mixed intercropping. The highest sesame yield (3128.93 kg/ha) was obtained with 50% sesame and 50% bean treatment and the highest bean yield (1087.76 kg/ha) was obtained with sole cropping. The highest amount of LER (land equivalent ratio) (1.59) was obtained with 50% sesame and 50% bean. LER values in all different treatments of multiple cropping were more than 1 and this shows superiority of multiple cropping compared with sole cropping of sesame and bean. This can be caused by biological nitrogen fixing by bean (Tavasoli et al., 2010). The highest value of Relative Crowding Coefficient (RCC) (2.19) was obtained with the50% sesame and 50% bean treatment. Based on Aggressively index (AG), bean was the dominant species.
Conclusions
Bean (as a nitrogen-fixing species) and sesame (as an oil crop) are different groups of plants with various functions. The presence of these two species in the intercropping increased diversity and optimal yield was obtained when the appropriate ratio (Balance between inter specific and intra specific competition) was used.