Effect of fungus Piriformospora indica on yield of soybean and millet in intercropping via competition indices

Abstract
Background and objectives: Nowadays the use of low-input farming systems and innovation modern management techniques of resources utilization in order to achieve the aims of sustainable agriculture has been particularly important. Bio-fertilizers application and intercropping systems are important approaches to achieve the objectives of ecological agriculture, which can improve temporal and spatial agricultural productivity. The use of bio-fertilizers in intercropping not only increases soil fertility, and reduces the use of chemical fertilizers, but also can lead to improve yield and quality of products. The endophyte fungus, are known as one of the most important classes of soil microorganisms, induce physiological and ecological alterations in their host plant and thus increase its yield. This study was conducted to evaluate the effects of fungus Piriformospora indica on yield, yield components and phosphorus content of soybean and millet in intercropping.

Materials and methods: The experiment was carried out as a factorial based on a randomized complete block design with three replications, in 2015 at the Research Station of Agricultural Faculty of Bu-Ali Sina University. The factors included of two levels of fungus P. indica (inoculated and non-inoculated) and five levels of replacement intercropping series consisted of monoculture of soybean (S), monoculture of millet (M), 67 % S+ 33 % M (67S:33M), 50 % S+ 50 % M (50S:50M) and 33 % S+ 67 % M (33S:67M). Different patterns of intercropping are replacement method and planting ratios were adjusted by altering the number of rows cultivation.

Results: The results demonstrated that in all intercropping treatments, the highest phosphorus concentration of soybean and millet (0.39 and 0.32 percent, respectively) were achieved in 50S:50M intercropping. Application of P. indica caused an increase in phosphorus concentration of soybean and millet about 31.6 and 22.9 percent respectively, compared to control. P. indica, caused an increase in the number of ears per plant of millet in different intercropping patterns. In inoculated with P. indica the increased the number of ears per plant of millet at 50S:50M intercropping by 28.3 percent in comparison with no-inoculation. The highest number of pods per plant in soybean (54 and 53 pods in plant) obtained in 50S:50M and 33S:67M ratios with P. indica, respectively. Fungus P.indica increased number of seeds per pod of soybean up to 16.4 percent in compared to control. In all intercropping treatments, land equivalent ratio was more than one. Maximum value of land equivalent ratio (1.14) was achieved in 50S:50M intercropping in inoculated plants with P. indica. Calculating the aggressivity index showed that millet was more dominate than soybean.

Conclusion: Application of fungus P. indica and replacement intercropping of soybean and millet, could improve yield and effectiveness indices of mixed cropping of above mentioned crops, because of increasing nutrient uptake efficiency.