The effect of extracted humic acid from different sources on the characteristics of sunflower grown in a calcareous soil

Introduction Calcareous soils, show serious limitation in accessing of nutritional elements. Majority of Iran’s soils are placed in arid or semi-arid regions and they are also in Alkali and lime conditions. As this calcareous soil mostly placed in hot climate conditions, naturally they are poor in organic matter. Humic materials are main and persistence components in organic matter and they could increase the growth of plants as well as the nutritional elements sorption. Humic acid is a natural organic Polymer Which as a result of the decomposition of soil organic matter, pit and lignin will be created and they will improve yield and quality of plant products. Humid matters will increase the resistance of plants in inappropriate environmental conditions. In spite of extended research on extraction and use of humic acids in plant nutrition, there is a limit attention in comparison effects of humic acid extracted from different sources on plant yield in calcareous soils. Hence the aim of this research is the effects of extracted humid acids from different sources on sunflower yield in soils with permanent lime stress. Materials and methods This research performed in greenhouse of university on sunflowers. The method was completely randomized factorial design with 3 replications in 2014-2015. Treatments were included: Soil application and foliar application with 5 sources of humic acids (Biochar 400 degree, biochar 200 degree, Sludge, manure and control). Humic acid treatments both in Soil application and foliar application were performed in 4 stages. Moreover of plant traits, (including Number of leaves per plants, stem length, fresh and dry weight, ash weight, Chlorophylls a, b, total and carotenoids and concentrations of phosphorus and potassium elements), there are also physical and chemical properties of extracted humic acids (including humic acid percentage, carboxylic groups, total acidity, OH-phenolic groups, and E4/E6, E3/E5 ratios) that they were measured. Results and Discussion Studying results of the physical and chemical properties of extracted humic acids, shows that the highest amount of extracted humic acid was observed in sludge treatment which had the highest proportion among other resources. Also according to the results, the highest amount of phenol groups, carboxylic groups and total acidity were observed in humic acid extracted from manure. The highest ratio of E3/E5 (the largest molecular size of humic acid) is related to humic acid extracted from biochar 400 degree. The smallest molecular size (E3/E5) was observed in the treatments of humic acid extracted from biochar 200 degree. The results showed that the humic acid extracted from any sources, had a positive effect on all traits of the plant and increased all traits significantly. In Foliar application treatments, The highest increase in leaf number, chlorophyll a, b, total and carotenoids and potassium was observed; where Soil application of humic acid sources showed the highest increase in stem length, dry weight, ash weight and phosphorus of plants. Humic acid extracted from sludge had a significant effect on stem length (63%), chlorophyll a (47%) and phosphorus (1.25 times). Also in compare with control, the humic acid extracted from biochar 200 degree, had a positive effect on the number of leaves (59%), fresh weight (60.23%) and dry weight (1.21 times), chlorophyll b (1.13 times), total (35%) and carotenoid (62%) and potassium (36%). Interaction effects of biochar 200 degree, had a positive effect on traits like the number of leaves (61%), dry weight (1.4 times), chlorophyll a (62%), total (64%), potassium (45%); also biochar 400 degree, had a positive effect on traits like chlorophyll b (1.5 times) and carotenoid (50%); soil application used biochar 200 degree had a positive effect on traits like fresh weight (75%); sludge had a positive effect on stem length (58%) and phosphorus (1.75 times) and manure had a positive effect on traits like ash weight (3.22 times), and this things all together had a positive effect on plant growth and yield. Conclusion In general, according to the results, the foliar application of Humic acid extracted from biochar 200 degree had the best performance on increasing the yield and its components, which may be attributed to the small molecular size of the extracted humic acid from biochar 200 degree.