Introduction
Soil erosion is one of the most important threats to soil quantity and quality that unwanted consequences can be considered as one of the biggest problems of different ecosystems today. Due to population growth and the need for food security, soil erosion is considered a global problem and this problem is more acute in developing countries. Therefore, applying appropriate management methods to control soil erosion is of great importance in managing and preserving natural resources. Since the biological and managerial containment of soil erosion and the use of native or non-native vegetation in critical conditions and especially in areas prone to erosion are very difficult or impossible to control, it is necessary to use methods among the various management measures available. to be able to protect the soil in its place and in the first steps of the effect of erosive factors on the soil matrix. One of the most important factors controlling runoff and soil erosion is the use of soil amendments. It should also be noted that these amendments do not have a destructive effect on the soil. Therefore, the present research was conducted with the aim of evaluating the separate and combined performance of organic (biochar) and inorganic amendments (polyacrylamide and polyvinyl acetate) on the changes in runoff and erosion on loess soils in the rain and erosion simulation laboratory.
Materials and methods
The soil used in this research was collected from the surface layer (zero to 10 cm) of the loess soil of the pasture lands of Ghozghan Valley, Daregaz city which is sensitive to erosion. After being transferred to the laboratory, to maintain the relative stability of the soil grains, they were passed through a 4 mm sieve. Plots with width, length and height of one, two and 0.25 meters were used for this research. The desired slope of 9% was used, which is roughly proportional to the general conditions of the region. Then, to create an impermeable layer, the plots were filled with mineral pumice to a depth of 15 cm. In order to carry out the present research, biochar treatment was used as an organic soil amendments, and polyacrylamide and polyvinyl acetate were used as inorganic soil amendments. Protective treatments were applied in laboratory conditions using a rain simulator with a rainfall intensity of 84 mm/h and with a duration of half an hour and plots of 1*2 m with a slope of 9%. In the review of sources from the researches, anionic polyacrylamide is used in the amount of six grams per square meter and in powder form due to its effect in reducing runoff and sediment, as well as polyvinyl acetate in the amount of six grams per square meter. Biochar obtained from forest trees was used in the amount of 700 grams per square meter.
Results and Discussion
The use of protective treatments prevents runoff from flowing on the loess soil surface, as a result, it increases the start time of runoff and decreases the volume of runoff, and ultimately leads to a decrease in the runoff coefficient. The results of the studied treatments showed that the use of organic and inorganic compounds had an effect on the measured biological properties and these effects were both decreasing and increasing. The use of compounds such as biochar has a positive effect on the biological properties of soil due to its high organic matter content and increases the activity of microorganisms and consequently increases parameters such as microbial biomass carbon. The composition of biochar can lead to the improvement of the physicochemical and microbiological properties of the soil. The results showed that the use of organic and inorganic soil amendments separately and in combination was able to reduce the sediment concentration up to 94.69%, reduce the runoff coefficient up to 59.2% and reduce soil erosion up to 89.6%, increasing the Water permeability increases to 5.3%, pH increases to 7.9%, and organic carbon increases to 2.9%. The rate of loss of three food elements nitrogen, phosphorus and potassium increased, especially in organic treatments compared to the control. Based on the results obtained from this research, the best treatment is the combination use of polyvinyl acetate and biochar.
Conclusion
The results of examining the treatments studied in this research showed that, in general, using organic and inorganic amendments separately and in combination, reduced the amount of erosion. In general, regarding the effect of the treatments used in this study on the amount of soil loss, it can be said that modifying the physical and even chemical properties of the soil increases its resistance to erosion and erosive factors. Regarding the importance of the physical and chemical properties of the soil, it can be said that the physical properties are in the first place and their modification is more important in reducing the amount of erosion; Nevertheless, changing and modifying the chemical properties of the soil, which is done by various organic additives, can also play its role in reducing the erosion rate by affecting the physical properties. In general, it can be stated that the use of organic and inorganic soil amendments separately and in combination to protect water and soil can be a useful solution. Finally, it is suggested the use of other soil amendments and different levels in loess lands and check the quality and elements of runoff after adding treatments in the field. |
