Investigation of important morphological traits and grain yield of lentil under shading and bio-priming

Lentil (Lens culinaris Medic) is a member of the leguminosae (Fabaceae) family and an important pulse crop grown in Iran. Growth of lentil plant is highly sensitive to environmental conditions, especially solar radiation, high temperature and water availability. One of the important reasons for unstable lentil yield is the indeterminate growth habit of lentil plants. Extensive vegetative growth, lodging, pod abortion due to limited light interception in the lower part of the canopy, excessive flower and pod shedding, and competition between pods and vegetative parts for photosynthates are all the consequences of indeterminacy and late maturity. Radiation (sunlight) is one the limiting factors in mixed and agroforestry cultivation systems. Crop yield is a function of radiation intercepted over the growing season, the efficiency of converting the intercepted radiation to biomass and the partitioning efficiency of biomass to seed yield. Therefore, in agroforestry production systems, maximizing the limited solar radiation with improved crop management practices such as seed inoculation with plant growth promoting rizobacteria (PGPR) could lead to yield improvement. Intensive use of chemical fertilizers has produced environmental problems and increased the production costs. The recent economic crisis and environmental problems has raised interest in environmental friendly sustainable agricultural practices, which can reduce input costs. N2-fixing may be important for plant nutrition by increasing nitrogen uptake by the plants, and playing a significant role as plant growth promoting rhizobacteria in the bio-fertilization of crops. Plant growth-promoting rhizohacteria are able exit a beneficial upon plant growth. Nitrogen fixation and P. solubilization production of antibiotic and increased root dry weight are the principal mechanism for the PGPR. A number of different bacteria promote plant growth, including Azospirillum sp., Azospirillum species are plant growth-promotive bacteria whose beneficial effects have been postulated to be partially due to production of phytohormons, including gibberellins.
An experimental field to study the effect of light intensity on lentil cultivars was conducted using a factorial arrangement based on a randomized complete block design with three replications at Agricultural Research Station of Ilam University during the 2012-2013 growing season. Studied factors included shading (control (without shading), 25, 50, 75 and 100% by shading) and bio-priming (control and inoculation with Azospirillum). Lentil Seeds (Lens culinaris Medik.) cultivar ILL4400 were sown on 21 February, 2013. 5 rows with 25 cm width and 2 m long designed in a 2×1.3 m plots and seeds planted with 2 cm intervals in North to South direction. Special net cloth with exact thickness was used for shading. The nets were cut and attached on 2×2 m frames according to the plot size and placed 1 m height on plots. During the growth season, hand weeding was done in necessary times, too. Samplings were included plant height, number of branches per plant, number of flowers per plant, leaf dry weight, shoot dry weight, active node in the root, total nodes in root and grain yield. For analysis of variance SAS software version 9.1 was used and graphs charted with excel.
Interaction effects between shading ×bio-priming had the significant effect on studying traits. Increasing the shading and application of Azospirillum increased plant height and total nodes in the root, so that the highest plant height (44 cm) and total nodes in the root (11.3 nodes) were obtained from 100% shading and application of Azospirillum. In this study, the number of leaves per plant, the number of branches per plant, total of flowers per plant, leaf dry weight, shoot dry weight, active node in root and grain yield decreased with increasing shading × check treatment so that the highest number of leaf per plant (91 leaves), number of branch per plant (15.6 branches), total flower per plant (65 flowers), leaf dry weight (1.6 g), shoot dry weight (2.2 g), active node in root (16.6 nodes) and grain yield (2994 kg/ha).
This study indicated that Azospirillum had a positive effect on lentil and morphologic traits and grain yield revealed a better status in the presence of Azospirillum. In fact, Azospirillum could alleviate the partial of grain yield in presence of shading. In general, using bio-fertilizers and manage integrated nourishment quantitatively and qualitatively is one of the efficient ways to improve plant production. Moreover, the environment would have a better condition if chemical fertilizer consumption reduces. Recent studies demonstrated that using bio- fertilizers not only improve the soil physiological structure but also increase organic matters content and nitrogen available to coexistent plant. Undoubtedly, before massive production and widely application of such products, it is necessary to implement and replicate this experiment in different regions.