The role of humic acid for enhancing biofertilization performance was studied on growth and yield of wheat in newly sand clay soil. Application of arbiscular mycorrhiza (AM) (Glomus mosseae) and plant growth promoting rhizobacteria (Azotobacter chroococcum) in combination with humic acid was evaluated. The resultsindicated that mycorrhizal root infection percentage significantly increased by application of humic acid with AM fungus. Inoculation with the biofertilizer agents increased phosphatase and dehydrogenase activity in wheat rhizosphere especially with AM inoculation. The highest values of enzymes activity were observed when the plants were treated by humic acid in the presence of biofertilizers especially with the dual inoculation. There were remarkable increases in available nutrients in rhizosphere of plants those inoculated with any of the two biofertilizers in combination with humic acid. Application of A. chroococcum and AM either alone or dual inoculation in the presence of humic acid gave considerable improvement in growth characteristics, photosynthetic pigments as well as nutrients uptake, total charbohydrates and crude protein of wheat plants when compared with either inoculated or uninoculated treatments without humic acid. Concerning endogenous phytohormones in wheat shoots, inoculation with A. chroococcum
individually gave maximum value of auxins, while application of humic acid especially with dual inoculation of biofertilizers didn't have positive effect on auxins content. On the other hand, humic acid enhanced the effect of biofertilizers on increasing of cytokinins and gibberellins content in wheat shoots and reducing of abscisic acid. Moreover, application of humic acid gave the highest values of grain and straw yield when associated with dualinoculation or A. chroococcum individually. Also, maximum values of grain quality were obtained from plants those treated with dual inoculation and humic acid. Therefore, application of humic acid can be considered as a good approach in enhancement of biofertilizers performance in newly reclaimed soil. |
