Investigation of Application of Humic Acid on Nutrient Uptake and Quantitative and Qualitative Indices in Kiwifruit

Kiwifruit (Actinidia Sp) is one of the fruits that it is considered as an appropriate food source, because it is rich in vitamins, especially vitamins C, E, A, B1 and also in the form of potassium. Humic substances are contained nutrients that improve the soil nutrients and are increases the availability of food and therefore plant growth and yield. Studies have shown that adding certain amount of humic acid fertilizer can improve the growth of root, stem and leaves of plants and enhances yield and quality of products and increases the efficiency of nitrogen fertilizer consumption. According to pervious findings, recent research was performed aimed to achieving the best combination of humic acid and its application method for improving yield and organic fruits production in Kiwifruit cv. Hyvard.

In order to investigate the effects of humic acid concentration and application method on nutrient uptake and quality and quantity of fruit indices, of Kiwifruit CV Hyvard an experiment based on complete block design with four replications was conducted during 2015-2016 in Talesh city, Gilan province. Experimental treatments included soil drenching method and foliar spraying of different levels (control, 2, 4 and 6 kg. ha-1 ) of humic acid. In this study traits such as absorption indexes of nutrient elements consisting nitrogen, potassium, phosphorus, calcium, zinc, magnesium, manganese, copper and iron content of leaves and quantitative and qualitative traits of fruit (yield, Tissue firmness, vitamin C, total soluble solids of fruits and leaf area and leaf chlorophyll content) were measured. Phosphorus was measured by spectrophotometer at 430 nm and potassium was measured by flame photometer. Atomic absorption was used to determine the amount of calcium (at wavelength of 422.7 nm) and magnesium (at wavelength of 285.2 nm). Nitrogen was also measured by Kjeldahl method. Micro elements were determined by flame atomic absorption method. Standard samples and treatments were cloudy with a blue acetylene flame and the adsorption of iron, manganese, zinc and copper were read at wavelengths of 243/3, 288.5, 213.9, 327.7 nm, respectively. This study was carried out in a randomized complete block design with seven treatments (0%) and application of humic acid at concentrations of 2, 4, 6 kg.ha-1 as spraying on leaves and soil application on Hayward cultivar with four replications. Data from this study were analyzed by using Jmp statistical software and graphs were drawn using Excel 2013 software.

Results of analysis of variance showed that different concentration of humic acid had significant effect on nutrient uptake and quality and quantity of fruit indices at 1% probability level. Results of this research indicated that using of humic acid caused increasing in nutrient elements uptake and improving the quality and quantity of fruit in Hyvard cv. of Kiwifruit. Comparison of means showed that the highest value of nitrogen (1.8%) of foliar application of 2 kg.ha-1 and 4 kg.ha-1 to soil of humic acid, phosphorus (0.3%) obtained by foliar application of 2 and 4 kg.ha-1 , calcium (3.5%) by foliar and soil application of 4 kg.ha-1 . The highest value of potassium (1.92) with soil application of 6 kg.ha-1 , manganese (0.33%) and copper (12.8 Mg.Kg Dw-1 ) of foliar application of 4 kg.ha-1,iron (226 Mg.Kg Dw-1 ) of soil application 6 kg.ha-1 humic acid and the highest value of magnesium (34.7 Mg.Kg Dw-1 ) uptake index obtained from adding 6 kg.ha-1 humic acid to soil. The results indicated that foliar spraying of 2 kg.ha-1 humic acid had higher efficiency for zinc uptake (21.7 Mg.Kg Dw-1 ). Comparison of means showed that the lowest value of measured elements obtained in control treatment. Based on the results, the concentration of four kilograms per hectare of humic acid with soil and leaf application methods had the highest effect on quantitative and qualitative indices of kiwifruit.

Results showed that application of humic acid caused increasing in absorption of nutrients and improving the quality and quantity of fruit in Hyvard CV of Kiwifruit. Comparison of meanings showed that the application, soil application of 4 kg.ha-1 of humic acid, was more effective in absorption indices of nitrogen elements, phosphorus, calcium and quantitative and qualitative indices of kiwifruit. Treatment of 6 kg.ha-1 soil increased the adsorption of manganese and iron elements and soil treatment of 2 kg ha-1 humic acid had the highest absorption of magnesium. Data analysis showed that zinc and copper elements were more adsorbed in humic acid by 2 and 4 kg.ha-1 in spray application. In this study the lowest value of measured elements obtained in control trait.