Document Type : Original Article
Authors
1 PhD student of Plant Physiology and Crop Production, Department of Genetics and Plant Production, Faculty of Agriculture, University of Zanjan, city of Zanjan, Iran
2 Associate Professor, Department of Genetics and Plant Production, Faculty of Agriculture, University of Zanjan, Iran
3 Professor, Department of Genetics and Plant Production, Faculty of Agriculture, University of Mohaghegh Ardabili, city Ardabil, Iran
4 Associate Professor, Department of soil group, Faculty of Agriculture, University of Mohaghegh Ardabili, city Ardabil, Iran
Abstract
Introduction
In many arid and semi-arid regions of the world, including Iran, soil salinization is considered an important obstacle to optimizing the use of agricultural lands. Salinity stress affects the main plant processes, including photosynthesis and the production of photosynthetic process, and with negative effects on these processes, it causes a decrease in plant production. Salicylic acid plays an important role in regulating plant growth, development, ripening and plant defense responses. Application of appropriate concentration of salicylic acid increases tolerance to abiotic stresses, thus not only reducing the destructive effects of stress but also increasing tolerance to biotic stress. However, the concentration of salicylic acid used and its method of application, including foliar spraying, depend on the plant species, and therefore contradictory results can be reported. One of the management strategies for improving the conditions of saline soils is the use of organic amendments, including biochar. In most of the studies, it has been stated that biochar increases the availability of micro and macronutrient elements (directly) and improves physical, chemical and biological characteristics such as increasing cation exchange capacity, dispersion, improving soil structure (indirectly), so increasing microbial biomass and improving soil fertility cased to increasing growth.
Materials and methods
The experiment was carried out factorial experiment in the form of a randomized complete block design with four replications. Factors include biochar in four levels (control without biochar, simple biochar 2.5% by weight in soil and biochar 25% modified with phosphoric acid and sulfuric acid by weight in soil) and salicylic acid foliar spraying in three levels (control, 0.5 and 1 mM) and soil at three levels (normal soil as a control, saline soil at two levels of 4 and 8 dS m-1). Salinity treatment was applied in two stages of planting, at the same time as the first irrigation and when the seedlings were fully established in the soil. To prepare modified biochar, 10 grams of biochar were added with 200 ml of phosphoric acid and one molar sulfuric acid. Foliar spraying with salicylic acid was done based on the determined levels, in two phases, early and late flowering. The desired traits were selected by choosing the number of plants randomly after applying the treatments, and the samples were weighed to evaluate the dry weight after drying in the oven.
Results and discussion
The results of variance analysis showed that the highest plant height in the first and second year of the experiment was obtained from the treatment of 0.5 and 1 millimolar salicylic acid, respectively, combined with the application of simple biochar of 2.5% by weight in the condition of no soil salinity stress. The application of 0.5 mM salicylic acid with biochar modified with phosphoric acid caused the highest number of leaves per plant in the absence of salinity. With increasing soil salinity concentration, the dry weight of bean plants decreased significantly. The application of biochar, especially simple biochar of 2.5% by weight, reduced the negative effects of salinity on these traits. In high soil salinity, the application of salicylic acid, especially combined with the application of simple biochar, improved the grain in the pod. The application of biochar modified with sulfuric acid in all treatments resulted in a significant decrease in grain yield; however, salicylic acid at different levels of salinity combined with the application of simple biochar showed a significant positive effect on grain yield. The highest level of salicylic acid with biochar modified with sulfuric acid showed negative results at different salinity levels on the number of root nodules and root dry weight.
Conclusion
By increase of soil salinity, the dry weight of bean plant decreased significantly, although at high concentrations with the application of biochar, especially simple biochar of 2.5% by weight, the negative effect of salinity on the plant weight decreased to some extent. The application of different levels of biochar in extreme salinity conditions not only did not improve the condition of this trait, but also caused a decrease in this trait compared to the absence of biochar application. Biochar, especially simple biochar, had a positive effect on increasing the number of pods in the plant in conditions of no salinity or moderate salinity. It was concluded that the positive and significant effects of different levels of salicylic acid on the morphological characteristics of the root, including its length, volume and weight, were particularly evident in high soil salinity stress.
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