Document Type : Research Article
Authors
1 Professor ,Department of Horticultural Science, Faculty of Agriculture, University of Zanjan
2 Department of Horticulture, Faculty of Agriculture, University of Zanjan, Zanjan, Iran
3 Temperate Fruits Research Center, Horticultural Science Research Institute, Agricultural Research, Education and Extension Organizations, Karaj, Iran
4 Department of Horticulture, Faculty of Agriculture, University of Zanjan, Zanjan Iran.
Abstract
Introduction
The Persian walnut (Juglans regia L.) is a valuable commercial crop with high economic and nutritional value. Nutrition management is one of the most important factors affecting the growth and performance of modern walnut orchards. The demand for high-quality walnuts is increasing day by day in the national and international markets. Horticultural production has undergone tremendous changes in recent years due to the development of innovative technologies, including nutrient management practices. Nutrient management of walnuts is one of the important factors for increasing yield and improving the quality of walnut kernels. The use of nitrogen, phosphorus and potassium fertilizers is essential for tree growth and the production of fruits such as walnuts. The enhancement in the use of fertilizers in an irrational manner has led to a decrease in soil productivity and multiple nutrient deficiencies. Minimizing the use of chemical fertilizers in fruit cultivation is the goal of integrated fruit production. The gravity of environmental degradation caused by the faulty cultivation practices has led to focus on ecologically sound, viable and sustainable farming systemsIn this study, in order to investigate the efficiency and feasibility of replacing sulfate-containing fertilizers with thiosulfate-based fertilizers, the effect of calcium thiosulfate and potassium thiosulfate fertilizers on increasing the yield and quality of walnut fruit was evaluated in an experiment.
Materials and Methods
This experiment was conducted in 1402, in a randomized complete block design with three replications and 5 trees per experimental unit in an orchard with 6-year-old Chandler trees grown from tissue culture seedlings in the Khoramdareh Agro-Industrial Complex. The experimental treatments included T1: regular orchard nutrition (control) including 50 kg/ha potassium nitrate calcium + 200 kg/ha potassium sulfate, T2: 100 L/ha calcium thiosulfate plus 200 kg/ha potassium sulfate, T3: 50 kg/ha potassium nitrate and calcium plus 100 L/ha potassium thiosulfate plus 125 kg potassium sulfate, T4: 100 L/ha calcium thiosulfate plus 100 L/ha potassium thiosulfate plus 125 kg potassium sulfate. After applying the treatments, after observing signs of ripening, the fruits of the tree were harvested and transferred to the laboratory for evaluation of biochemical and physical traits.
Results and Discussion
Analysis of variance for fruit and yield traits showed significant differences at the 1 and 5 % levels. Comparison of the means of these traits showed that the highest fruit dry weight, fresh and dry kernel weights, and kernel percentage were obtained in the calcium and potassium thiosulfate treatment, and the highest tree yield and yield efficiency per trunk cross-section were obtained in the calcium thiosulfate treatment. Calcium increases the growth of hairy roots, root cell division, root length and also enhance the absorption and transfer of nutrients and water to the plant, This led to an improvement in fresh and dry weight of the plant and yield. Calcium also increases the fresh and dry weight of the plant by increasing the transfer of carbohydrates from leaves to fruit. On the other side, potassium increases fresh and dry weight and yield by enhancing photosynthesis, carbohydrate formation and transport, maintaining intracellular pH, and absorbing nutrients from the soil. In addition, the results of the comparison of means showed that all treatments used increased the total phenol and flavonoid content of walnut fruit compared to the control, so that the highest total phenol and flavonoid content were obtained in the potassium thiosulfate and potassium and calcium thiosulfate treatments. Calcium reduces oxidative stress in the membrane through membrane strength and delays the degradation and reduction of phenolic compounds by strengthening the membrane and cell wall. Moreover, Potassium increases plant growth and photosynthetic activity, increasing the allocation of additional carbon to the shikimic acid pathway, thereby increasing phenolic substances such as phenols and total flavonoids. Potassium also increases phenolic compounds and antioxidants by increasing the activity of the enzyme phenylalanine ammonia lyase, which is a key enzyme in the synthesis of phenolic compounds. Analysis of variance of data related to crude fiber, total protein and crude fat of fruit showed significant difference between treatments at 1% level, but the effect of treatments on ash content of samples was not significant. Results of mean comparison showed that the highest amount of crude fiber was related to potassium and calcium thiosulfate treatment. Increased absorption and transport of nutrients is one of the important factors in increasing crude fiber in plants, and it seems that rapid absorption and transport of thiosulfate-containing compounds has led to improved fiber production. Analysis of variance of data related to linoleic and oleic acid traits of walnut fruit showed significant difference between treatments at 1% level and results of mean comparison also showed significant increase in linoleic acid content in fruits under calcium and potassium thiosulfate treatment and potassium thiosulfate treatment. There are two important sources for assimilation and oil formation. The first is the carbohydrate pathway that is produced in the leaf after photosynthesis and transferred to the fruit, and the second is the carbohydrate pathway that is formed during photosynthesis in the walnut fruit, which is converted into fatty acids after enzymatic processes. In this study, increasing sulfur, potassium, and calcium and increasing the absorption of trace elements due to thiosulfate consumption increased photosynthetic activity and increased the production of plant metabolites, which increased the fatty acids in walnuts. Therefore, the obtained results indicate high efficiency of calcium and potassium thiosulfate fertilizers in increasing quality and yield of walnut fruit.
Conclusions
Our findings indicated that calcium thiosulfate - potassium thiosulfate combination were the best treatments for increasing quantitative and qualitative characteristics of walnut fruit. These findings demonstrate the potential of calcium and potassium thiosulfate fertilizers to enhance walnut orchard productivity and fruit quality, making them a recommended choice for nutrient management strategies.
Keywords: Fatty acids, Nutrition, Biochemical traits of fruit, Yield efficiency
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