عنوان مقاله [English]
Introduction: The amount of soil nutrients and their availability for plants are the important aspects of soil fertility. Although micronutrients are used by plants in very small amounts, they play an active role in many plant-based processes and reactions influencing the plant growth and yield. The efficiency of absorption of micronutrient can be increased by adding some organic and mineral materials to soil. Saha et al. (41) observed an increase in micronutrient concentration of corn grain by adding organic materials to soil. Zeolite is one of the most commonly minerals used to increase agricultural production (17). The zeolites, due to their structure and porosity, are well-suited for retaining the nutrients and gradually releasing them into the root zone (40).Despite the positive effects of zeolite on some physical and chemical properties of soil, its application at high levels may adversely affect the absorption of nutrients and plant growth. Hamidpour et al. (18) who used zeolite for Zinnia flower, reported that zeolite reduced the yield of Zinnia flower. Basari et al. (4) reported that zeolite application increased soil pH and electrical conductivity (EC). Therefore, this research was carried out with the aim of assessing the influence of zeolite application, type (i.e. vermicompost and cow manure) and organic matter levels on the growth and the micronutrients uptake and determining the appropriate composition for corn.
Materials and Methods: A factorial experiment was conducted in a completely randomized design with three replications in greenhouse under controlled condition.The treatments consisted of raw zeolite (natural) in three levels (0, 6, 12% by weight), organic matter including vermicompost in three levels (0, 0.125, 0.25% or 0, 5, 10 t ha-1) and cow manure at three levels (0, 0.5, 1% by weight or 0, 20, 40 t ha-1).The soil was collected at a depth of 0-30 cm from the Mashhad Soil and Water Research Center. General soil characteristics and micronutrients concentration (iron, zinc and manganese) were determined according to standard methods (14, 27). For vermicompost and cow manure, some parameters such as pH and EC, organic carbon (46), available phosphorus and potassium (21), total nitrogen (7) and micronutrient (iron, zinc and manganese) were also measured (21). Further, pH, EC and micronutrient (iron, zinc, and manganese) were measured for natural zeolite (27). The pots were prepared by mixing 5 kg soil and experimental materials. N, P, and K were added according to soil testing. Irrigation with distilled water at field capacity level was done during the growth period. The plants were harvested75 days after sowing and after separating shoot and root, the plant materials were transferred to laboratory. Root and shoot dry weight were determined and after dry digesting of plant materials, the concentration of micronutrient were quantified by Atomic Absorption (21). The soil samples were also analyzed in order to determine the chemical properties of the soil after harvesting. Statistical analysis of the data was performed using JMP software and the mean comparison was carried out based on LSD test at 5% probability level.
Results and Discussion: The results of the experiment showed that increasing zeolite levels reduced dry weight, decreased height and uptake of zinc, iron and manganese and increased soil pH and iron and manganese concentrations. In addition, it was observed that the zeolite application had a negative effect on the plant growth and micronutrients uptake. Burriesci et al. (8) concluded that the zeolite application without fertilizing seems not to considerably increase plant growth. According to Kimberly and Nelson (24), the use of natural zeolite, without adding nutrients, leads to a competition between plant roots and zeolite for the nutrients absorption. Sarmetzidis et al. (42) showed that zeolite had no effect on the growth and yield of roses. Kolar et al. (25) reported that increasing the amount of zeolite in the geranium cultivar increased pH and the plants growth. At lower levels of zeolite, shoot fresh and dry weight was larger than that in higher levels of zeolite. Our results also denoted that the maximum amount of plant dry weight, plant height, the micronutrient (zinc, iron and manganese) uptake and the lowest soil pH were observed for the treatment of cow manure (1 %) in the absence of zeolite which had a significant difference relative to other treatments and also control. Shirani et al. (44) reported that the application of cow manure significantly increased corn dry matter. Ortiz and Alkaniz (36) showed that using organic fertilizers enhances the amount of absorbent metals such as iron, zinc and manganese as these metals are in a soluble and exchangeable form in these fertilizers. By releasing organic acids, the organic fertilizers, especially cow manure, reduce the localized pH of soil and increase the iron uptake by plants during the mineralization process.
Conclusion: According to the results, the use of zeolite increased soil pH, decreased corn growth and micronutrient uptake. Applying organic materials with zeolite can reduce the mentioned negative effect of zeolite. Cow manure at lowest level was more efficient than vermicompost at all levels. Overall, adding cow manure can improve the plant growth and micronutrient uptake by plant when the zeolite is intended to be used to modify soil physical characteristic.