Evaluation of Growth Indices of Common Bean (Phaseolus vulgaris L.) and Moldavian balms (Dracocephalum moldavica) at Different Intercropping Patterns in Presence of Microorganisms

 The use of intercropping and the potential of microorganisms such as Arbuscular mycorrhizal fungi (AMF) and Plant growth promoting rhizobacteria (PGPR) is one of the important strategies in sustainable agriculture. Intercropping is multiple cropping systems, in which two or more crop species planted simultaneously in a field during a growing season. Of course, this does not mean that in the intercropping, plants can be planted at a time together, but is the purpose that two or more crops are together in one place, during their growing season or at least in a time frame. Therefore, it is possible that plants are different in terms of planting date, and a plant is planted after the other plant. Potential benefits of intercropping are such as high productivity and profitability, improvement of soil fertility, efficient use of resources, reduction in the damages caused by pests and weeds, better lodging resistance and yield stability. On the other hand, the use of AMF and PGPR as biofertilizers can play a role in improving plant nutrition, plant growth and product quality. The aim of this study was to study the effect of AMF and PGPR inoculation on plant growth indices in bean-Moldavian balm intercropping.

 This experiment was conducted in the Agricultural Research Greenhouse of Urmia University, Located in 11 kilometers Sero road of the city of Urmia, Iran (latitude 36° 57′ N, longitude 45° 24′ E and 1321 m elevation) in 2017. The climate of the area is a Hot-summer Mediterranean climate bordering continental climate with cold winters, mild springs, hot dry summers, and warm autumns. This experiment was carried out in a factorial based on a randomized complete block design with three replications. The factors including microbial inoculation {(AMF, PGPR, AMF+PGPR and without microbial inoculation) and planting patterns (Sole cropping of Moldavian balms and bean, 1 row bean+ 1 row Moldavian balms (1:1), 2 rows bean+ 1 row Moldavian balms (2:1), 1 row bean+ 2 rows Moldavian balms (1:2) and 2 rows bean+ 2 row Moldavian balms (2:2)}. For this purpose, soil samples were prepared from Naqhadeh city in West Azerbaijan Province in Iran. In order to greenhouse tests, the soils added to the pots (in each pot containing 45 kg of soil). In treatments, soil used with microbial inoculation. Microbial strains were used for microbial inoculation including PGPR (P. aeruginosa, P.fluorescens and P. putida) and AMF (Funneliformis mosseae, Rhizophagus irregularis and Claroideoglomus etunicatum). For plant cultivation, been (Phaseolus vulgaris L.) and moldavian balms (Dracocephalum moldavica) seeds cultivar were grown in pots. At the end of the growth period, the characteristics of the agronomic traits in the bean plant were including plant height, number of seeds per pod, 1000 seed weight, biomass yield and Seed yield, and in Moldavian Balm were including, plant height, biomass yield and essential oil percentage were determined. In addition, the land equivalent ratio (LER) was calculated to determine the advantages of intercropping. The analysis of variance for the obtained data was done by statistical analysis system (SAS 9.4) software. The mean comparison was done using the Duncan test at the 5% probability level.

 The results showed that the different intercropping and microbial inoculation had a significant effect on all traits, in Moldavian balms and common beans. All the plant growth indices in common bean-Moldavian balm intercropping were the highest in the combined treatment of AMF +PGPR, compared to another treatment. The highest and the lowest seed and biomass yield of bean were achieved in sole cropping with 3.20 and 9.70 g and 1:1 with 1.57 and 4.41 g, respectively. The maximum biomass yield and other traits of Moldavian balm obtained under sole cropping, while essential oil percentage was higher in all intercropping patterns than in sole cropping patterns. The main constituents of Moldavian balms essential oil were Geranyl acetate, Geranial, Geraniol and Neral. The highest LER value (1.67) was obtained from 2:2 intercropping in PGPR inoculation.

 In general, the results showed that all of the plant growth indices of Moldavian balms and bean in sole cropping were higher than other intercropping patterns; however higher LER was observed in intercropping with microbial inoculation. This shows more exploitation of unit area in intercropping. In addition, the greater amount of LER in replacement intercropping than additive intercropping highlights the necessity of appropriate density of plants per unit area in the intercropping. It can be concluded that application of intercropping with combined application of AMF and PGPR leads to improvement on yield and yield components of plant.