The effect of different levels of phosphorus and biofertilizers on photosynthetic parameters and seed yield of Mungbean (Vigna radiata L.)

The mungbean (Vigna radiate L.) is one of the most species of legumes. The seeds are an excellent sources of phosphorus. The phosphorus application to legumes have positive effect on nodulation through enhance root proliferation and thus helps in increase nitrogen fixation, So that Phosphorus deficiency is considered as one of the major constraints to successful production of legume. Biofertilizers have high potential for increasing the efficiency of Phosphorus, and ultimately stimulate plant growth. Therefore, this study was conducted to evaluate the biofertilizers in the release of soil insoluble phosphorus and to investigate the effect of plant growth promoting bacteria, Mycorrhizal fungi on photosynthetic pigmentation and nutrient elements during the period of mungbean growth.

To study the effect of different levels of phosphorus and biofertilizers on photosynthetic parameters and seed yield of Mungbean (Vigna radiata L.) a field experiment was carried out as a factorial based on a randomized complete block design (RCBD) with three replications at research field of the Faculty of Agriculture of Gorgoan University in 2016-2017. The treatments of this research consisted of three levels of phosphorus (Control, 150 kg.he-1 and 225 kg.he-1) and eight levels of plant growth promoting bacteria and Mycorrhizal fungi (Control, Azospirillum lipoferum, Pseudomonas fluoresens, Glomus mosseae, Azospirillum and Pseudomonas, Azospirillum and Glomus mosseae, Pseudomonas and Glomus mosseae, and Azospirillum lipoferum, Pseudomonas fluoresens, Glomus mosseae). In this experiment, Rhizobium bacteria (R. leguminosarum) was used in all plots. Grain inoculation was done in shadow and after drying, inoculated grains were immediately cultivated. Mycorrhizal fungi was applied under the grain hole just prior to sowing.Chemical fertilizers were applied at a rate of 50 and 100 kg.ha-1 in N and K respectively. Random samples of ten plants for each experimental unit were taken and Photosynthetic pigments, including chlorophyll a, chlorophyll b, carotenoids, SPAD value, grain protein and nitrogen content in plant aerial parts, leaf area index and seed yield were recorded. Data were subjected to analysis of variance procedure using the SAS statistical software and for the mean comparison, the least significant difference (LSD) test method was used at 5% probability level.

The results showed that the effect of phosphorus fertilizer and Plant growth promoting bacteria, Mycorrhizal fungi on photosynthetic pigments (chlorophyll a, chlorophyll b, carotenoids), SPAD value, grain protein, nitrogen content in plant aerial parts at different stages of plant growth, leaf area index and seed yield were significant, but the interaction of phosphorus fertilizer and Plant growth promoting bacteria, Mycorrhizal fungi levels was not significant on any of the studied traits. The results showed that the highest amount of chlorophyll a, chlorophyll b, carotenoid, SPAD, grain protein and nitrogen content in plant aerial parts, leaf area index and seed yield were obtained at 225 kg.ha-1 phosphorus fertilizer. Application of Plant growth promoting bacteria, Mycorrhizal fungi led to an increase in the amount of photosynthetic pigments, seed protein and nitrogen content of plant aerial parts, leaf area index and seed yield.

The results of this study indicated that the photosynthetic pigments, seed protein, nitrogen accumulation in the plant and leaf area index were increased by increasing the amount of phosphorus fertilizer. Also, the optimal effect of Plant growth promoting bacteria and Mycorrhiza on photosynthetic pigments and increasing the protein content of seeds and nitrogen in different stages of plant growth Which ultimately led to an increase in seed yield.