Assess the Impact of Alfalfa Root System on the Reinforcement of Soil

Subject Areas : Farm water management with the aim of improving irrigation management indicators

Samad Zahermand ¹ , Khosrow Shafiei Motlagh ² , Esfandyar Jahantab ³ , Rasol Ajalloeian ⁴

1 - Lecturer of Department of Civil engineering, Dehdasht branch, Islamic Azad University, Dehdasht, Iran.
2 - Assistant Professor, Department of Civil engineering, Dehdasht branch, Islamic Azad University, Dehdasht, Iran.
3 - Assistant Professor, Department of range and watershed management, faculty of agriculture, Fasa University, Fasa, Iran.
4 - Professor, Department of Geology, University of Isfahan, Isfahan, Iran.

Received: 2020-02-09 Accepted : 2022-07-12 Published : 2022-09-23

Keywords: Biotechnology, Root Density Index, Direct shear test, alfalfa, Soil Reinforcement,

Abstract :

Background and Aim: Soil improvement using plant roots has been considered by many researchers in order to strengthen soil mass in terms of environmental protection and natural resources.The effect of plant root system on soil resilience is a function of the biotechnical properties of roots But due to the complex interactions between soil and plant, the impact of root reclamation on soils remains a challenge.This study investigates the effect of alfalfa root density on soil consolidation in Pazannan region in Khuzestan provinceMethods: In this study, for the first time, the effect of alfalfa root system was investigated on soil resilience in greenhouse conditions. Soil samples taken from the study area after a period of 5 months under greenhouse cultivation, 3 rootless soil samples and 12 soil samples with different root densities were tested for direct cutting to measure the shear strength of soil composition and roots And the parameters of internal friction angle and adhesion of root-reinforced soil were obtained and compared with rootless soil samples.Results: In general, the density and number of roots has been reduced with increasing depth, and also the root density index decreases with the depth increases.Using these results and direct cutting tests   was calculated the amount of armament.The presence of roots has created a significant resistance to soil shear strength, which has been affected by increasing the amount of soil adhesion.In contrast, the internal friction angle of reinforced soil decreases with respect to the rootless soil and has the opposite behavior of the adhesion factor.And its changes are much less than the changes of the adhesion factor.Therefore, it can be known that increasing the shear strength of soil reinforced with alfalfa root is equivalent to increasing adhesion.Conclusions: The results of this study show that there is a direct relationship between root density index and soil shear strength. The highest and lowest reinforcement rates for 28 and 5% density index were 87.5% and 7.5% increase in soil adhesion, respectively and there has been a maximum reduction in internal friction angle relative to rootless soil of 5.5%. This study showed that there is a decrease in the relationship between depth and root density index, depth and strength of reinforcement as biotechnological characteristics of alfalfa species.

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