عنوان مقاله [English]
Unbalanced and frequent use of chemical fertilizers and pesticides results in the degradation of soil physicochemical properties, loss of soil-born organisms, reduction of quality of produced crops and reduction of yield plant. Nowadays, due to environmental considerations of chemical fertilizers, use of organic acids for quantitative and qualitative improvement of crops has been increased. Humic materials are natural organic compounds that contain 50 to 90% of organic matters of peat, wood coal and rotten material, as well as non-living organic matters of aquatic and terrestrial ecosystems. Humic compounds indirectly increase soil fertility by providing micro- and macro-elements for root, improving soil structure, increasing medium permeability to water and air, increasing soil microbial population and beneficial microorganisms, increasing cation exchange capacity and the ability to buffer pH of medium or nutrient solution, and providing some special substances for plant roots such as nucleic acids and acetamides.
Materials and Methods
In order to investigate the influence of humic and fulvic acids on some growth characteristics in ornamental plant of Scindapsus spp., an experiment was conducted based on a completely randomized design with three replications at greenhouse in Ferdowsi University of Mashhad during 2014-2015. The first factor was humic acid in four levels of 0, 0.2, 0.5, 1 g/l, and the second factor was fulvic acid in four levels of 0, 0.2, 0.5, 1 g/l. Cuttings were taken from the plant in late March. Two weeks after transferring the rooted cuttings to pot, the treatments were applied on plants via fertigation. The traits measured in the experiment included plant height, mean number of nodes, internode length, leaf number, leaf length, leaf width, leaf area, root length, root fresh weight, leaf fresh weight, shoot fresh weight, aerial organ fresh weight, root volume, aerial organ volume, root dry weight, leaf dry weight, shoot dry weight, aerial organ dry weight, fresh and dry weights ratios of aerial organ to fresh weight. Statistical analysis of data was performed by 8-JMP software. LSD test was used to compare the means of the data.
Results and Discussion
Based on the results obtained, the combined use of humic acid and fulvic acid had a significant effect on height, fresh and dry weights of leaf, shoot, aerial organ and root, number of node and leaf and volume of aerial organ, fresh and dry weights of root, length and volume of root and the ratio of fresh and dry weights of aerial organ to root. Thus, combined use of humic acid and fulvic acid caused an increase in all the measured traits compared to the control treatment. Furthermore, an increase was observed in the length, width, and area of leaf, and internode length as the result of application of humic substances when compared to the control treatment. Organic fertilizers increase plant growth by improving soil conditions and increasing availability of plant to nutrients. Humic compounds cause changes in the specific distribution of cytokinins, polyamines and ATP by affecting the activity of root H+-ATPase and the distribution of root nitrate in the stem, thus affecting the growth of the plant stem. Humic materials increase plant growth by using different mechanisms such as hormonal effects, direct effect on plant cell metabolism, increase of cell division, chelating power and nutrient uptake, increase of soil ventilation and enhancement of plant photosynthesis by increasing Rubisco enzyme activity. Increasing nitrogen uptake leads to the increase in the growth of shoots and aerial organs. It also increases the number of branches in plants and increases the production of dry matter by increasing the production of photosynthetic materials.
In general, according to the results of this experiment, it can be concluded that application of humic substances (humic acid and fulvic acid) together, improved the growth characteristics of the plant and led to the better growth of the plant; therefore, these materials can be a good alternative to plant growth-stimulating chemical fertilizers.