Document Type : Research Article
Authors
Department of Soil Science, Faculty of Agriculture, University of Zanjan, Zanjan, Iran
Abstract
Introduction
Increasing the quality of food grains is one of the goals of sustainable agriculture. Mung bean (Vigna radiata L.) is one of the most important legume crops cultivated on more than 6 million hectares worldwide. There are few studies on the effect of mealworm frass application and its effectiveness on plant growth and yield. On the other hand, given the soil and climatic conditions of Iran, its high potential in legume production, and its economic justification, it seems necessary to pay attention to feeding mung beans with organic fertilizers. The cultivation of mung bean is increasingly developing in Iran, and its use for food and medicinal purposes is also increasing. Therefore, considering the possible positive effect of mealworm frass and zinc fertilizer on the growth of this plant, the present study was conducted to investigate the effect of these fertilizers on growth, yield indices, and the molar ratio of phytic acid to zinc in the seeds.
Materials and Methods
In this study, an experiment was conducted as a factorial experiment in a randomized complete block design with three replications. The aim was to investigate the effect of different levels of mealworm frass and zinc lignosulfonate foliar application on growth characteristics, yield, zinc concentration, the molar ratio of phytic acid to zinc, and some biochemical factors of mung bean seeds. The treatments included four levels of mealworm frass (0, 500, 1000 and 1500 kg ha-1) and three levels of zinc foliar application during the flowering period (foliar application with irrigation water as a control and foliar application with concentrations of 2.5 and 5 g L-1 of zinc lignosulfonate). Growth and yield indices including plant height, number of secondary stems, number of pods per plant, number of seeds per pod, pod length, and seed yield were measured. Also, some biochemical properties such as molar ratio of phytic acid to zinc, flavones, total flavonoids, total phenols, tannin concentration and percentage of antioxidant activity were measured. Nitrogen, phosphorus and potassium of mung bean seeds were also measured.
Results and Discussion
The results showed that the simple effect of mealworm frass was significant for all measured traits except the number of secondary stems, pod length, and number of seeds per pod. The simple effect of zinc lignosulfonate was significant for all measured traits except the number of secondary stems, pod length, number of seeds per pod and total phenol concentration, and seed tannin. The interaction effect of mealworm frass and zinc lignosulfonate for all measured traits except pod length and number of seeds per pod was significant. The highest grain yield (115.2 g m-2) was related to the treatment of 1500 kg of mealworm frass and 5 ppt zinc lignosulfonate foliar spray, which was in the same group as the treatment of 1500 kg mealworm frass with 0 and 2.5 g L-1 zinc foliar spray, and the treatment of 1000 kg mealworm frass and 5 g L-1 zinc foliar spray. While the lowest amount (80.1 g m-2) was observed in the control treatment. The highest plant height (37.05 cm) was measured in the treatment of 500 kg mealworm frass with zero zinc application, and the lowest stem length (24.68 cm) was observed in the treatment of 500 kg of mealworm frass with the application of 5 g L-1 zinc. The highest molar ratio of phytic acid to zinc (30.8) was observed in the treatment of 500 kg of mealworm frass and no foliar application of zinc lignosulfonate, which was not significantly different from the treatments of 0 kg of mealworm frass and 0 and 2.5 g L-1 of zinc lignosulfonate application. While the lowest ratio (24.1) was observed in the treatment of 0 kg of mealworm frass and 5 g L-1 zinc lignosulfonate application, which was not significantly different compared to the treatment of 1500 kg of mealworm frass and 2.5 and 5 g L-1 of zinc lignosulfonate application. Foliar application of zinc reduced the molar ratio of phytic acid to zinc in the grain (maximum 21%), and application of mealworm frass increased this ratio up to 500 kg and then decreased it. Based on the results of this study, the application of 1000 kg of mealworm frass without zinc application was more effective in increasing the concentration of flavonoids and antioxidant activity. However, zinc foliar application was effective in increasing the concentration of phenolic compounds and tannin. The highest antioxidant activity (72.44%) was observed in the treatment of 1000 kg of mealworm frass without foliar application of zinc, and the lowest (58.18%) was measured in the treatment of 1500 kg of mealworm frass and application of 2.5 g L-1 zinc lignosulfonate, followed by treatments of 500 kg of mealworm frass without foliar application of zinc lignosulfonate and foliar application of 2.5 g L-1 zinc lignosulfonate. Zinc foliar spraying was effective in increasing the concentration of phenolic compounds and tannin content. Foliar application of zinc lignosulfonate increased the zinc and nitrogen content of the grain but had no effect on the phosphorus and potassium concentrations. Application of mealworm frass increased the nitrogen, phosphorus, and potassium content of the mung bean grain but simultaneously reduced the zinc concentration.
Conclusion
In general, the results of this study showed that the use of mealworm frass increased mung bean grain yield, and foliar spraying of zinc lignosulfonate increased the grain zinc concentration and reduced the molar ratio of phytic acid to zinc. Overall, the use of mealworm frass increased the yield, and the use of zinc lignosulfonate improved the grain quality.
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