چكيده لاتين :
<strong >Introduction </strong >
Intercropping is a kind of multi-culture system where two or more plants are cultivated in a piece of land simultaneously. The aim of intercropping is optimizing the use of space, time and physical resources in both the top and under of the soil surface through maximizing positive relationship and minimizing negative relationship between the components of agricultural ecosystems. In intercropping due to better use of available resources such as land, labor, time, light, water and nutrients, as well as reducing damages caused by pests and diseases and socio-economic advantages, increase in production per unit area can be expected. In this study, yield and yield components of sesame and bean in additive and replacement intercropping with mixed and row planting type was evaluated and the possible advantages of intercropping to monoculture as well as the types of intercropping were compared.
<strong >Materials and Methods </strong >
This experiment was conducted in Agricultural Research Station of Ferdowsi University of Mashhad, located in 10 kilometers south-east of the city of Mashhad, Iran (latitude 36° 17′ N, longitude 59° 35′ E and 985 m elevation) in 2013 and 2014. Climate of the area is cold and dry. A Split-Plot experiment based on randomized complete block design with three replications was used with the factor of cropping system (as main plot) and intercropping proportions (as sub plot). The cropping system was included; mixed and row cropping and intercropping proportions were included; monoculture of bean (100b), 25% sesame- 75% bean (25s75b), 50% sesame- 50% bean (50s50b), 75% sesame- 25% bean (75s25b), monoculture of sesame (100s), 10% bean- 100% sesame (10b100s), 20% bean- 100% sesame (20b100s), 30% bean- 100% sesame (30b100s), 100% bean- 10% sesame (100b10s), 100% bean- 20% sesame (100b20s), and 100% bean- 30% sesame (100b30s). Planting was done using common varieties of the region (Esfarayen and Derakhshan varieties for sesame and bean, respectively). Hand-weeding method was used for controlling weeds. The first was done when most plants were, in the 6 leaf stage and in the height about 15cm, continued every 13 days until the growth of the canopy limited the growth of weeds. There was not used any fertilizer during the growing season. At the end of the growing season traits such as 1000 seed weight, number of capsules or pods per plant, number of seeds per capsule or pod, biological yield, seed yield and harvest index were recorded. In addition, the land equivalent ratio (LER) was calculated to determine the advantages of intercropping. Analysis of variance and Duncan 's mean comparison were used for statistical analysis.
<strong >Results and Discussion </strong >
The results showed that intercropping had a significant effect on all traits, in sesame and bean. 1000 seed weigh, number of capsules or pods per plant, number of seeds per capsule or pod and harvest index in the treatments of 25s75b, 50s50b and 75s25b, were the highest amounts. Number of seed per plant, seed yield and harvest index in sesame and 1000 seed weight, biological yield and seed yield in bean were affected by planting type which row planting had higher value than mixed planting. This can be due to better use of resources and avoid inter and intra species competition, in the circumstances stated above. The results showed that the total LER, LER of sesame, and LER of bean were higher in replacement intercropping planting than mixed planting. In addition, replacement intercropping had better performance in total LER, LER of sesame, and LER of bean, to additive intercropping. Also, total LER was more than 1 which highest values were observed in the treatments of 25s75b, 50s50b, 30s100b, 75s25b, 100s 30b and 10s100b (1.22, 1.19, 1.15, 1.15 and 1.14, respectively). It seems that better utilize of the growth resource in the inter cropping led to reach this result. The results showed that presence of bean in intercropping had positive effects on sesame, so that the symbiosis of bean roots with nitrogen-fixing bacteria could be the main reason.
<strong >Conclusions </strong >
In general, the results showed that seed yield of sesame and bean in monoculture were higher than other combinations of intercropping; However higher LER was observed in the treatments of intercropping. This shows more exploitation of unit area in intercropping. In addition, greater amount of LER in replacement intercropping than additive intercropping highlights the necessity of appropriate density of plants per unit area in the intercropping. Also row planting showed better performance compared with mixed planting that suggests the effect of planting correct arrangement for further exploitation of resources in the intercropping.
