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Introduction: Iran, with an area of more than 164 million hectares, is located in the dry belt of the earth. In recent years, the rate of wind erosion has increased significantly, so the use of methods for stable stabilization of sand dunes is essential. Therefore, this study was designed and performed with the aim of identifying soil bacteria affecting the microbial induced carbonate precipitation and evaluating different amounts of potash waste water (SSR400 solution) as a cheap solution on the stabilization of sand dunes.
Materials and methods: In order to investigate the possibility of stabilization of sand dunes using industrial wastwater and soil microorganisms, two experiments were designed and performed in 2019 at Yazd University. The first experiment was performed with the aim of screening soil bacteria in desert areas of Iran with the highest ability to hydrolyze urea. The tested bacteria included 4 bacterial isolates from Eshtehard desert, 6 bacterial isolates isolated from the central desert of Iran and Sporosarcina pasteurii bacteria. The second test was performed with the aim of evaluating the stabilization of sand dunes as a two-factor factorial in a completely randomized design with three replications. The first factor included the use of mulch at 4 levels of 0.5, 1, 2 and 1/3 of soil saturation (SP). The second factor was type of mulch in 8 levels: no bacteria, Pseudomonas fluorescens, Sporosarcina pasteurii, Phormidium tenue, Oscillatoria tenuis, b4, distilled water and potash waste water (SSR400 solution). Data analysis and statistical calculations were performed using SASV9 and EXCEL software. Mean comparison was performed by protected LSD test at 5% probability level.
Result: The results of urea hydrolysis ability test showed that the bacteria in urea hydrolysis had a significant difference in the level of one percent probability. Comparison of the mean results showed that Sporosarcina pasteurii with an average of 3223.3 μs/min of electrical conductivity (EC), had the highest ability to hydrolyze urea. In the next rank, the bacteria isolated from the soil of Eshtehard desert (b2) with 2421.3 and the bacteria (b4) with the amount of 2072.3 micro Siemens per minute belonged to the soil of the central desert regions of Iran. The results of comparing the 16S rRNA sequence of b2 bacterium with other bacteria in the NCBI gene bank database showed that the ribosomal RNA sequence of 16S b2 isolate is 99% similar to the sequences of Pseudomonas fluorescens. Analysis of variance of the second experimental data showed that the type and amount of mulch consumption and the interaction of the two had a significant effect at the level of 1% probability on compressive strength, tuber diameter and particle percentage greater than 0.84 mm. The highest compressive strength and the percentage of particles larger than 0.84 mm were obtained at the rate of 4.4 kg/cm2 and 97.5% with the application of Sporosarcina pasteurii at the rate of 1/3 soil saturation, respectively. Compressive strength of application of 1/3 soil saturation of potash waste water (SSR400 solution) and Pseudomonas fluorescens was 3.88 and 3.85 kg/cm2, respectively. The highest diameter of tuber at a rate of 5.5 cm was obtained in the application of potash waste water (SSR400 solution) at a rate of 1/3 of soil saturation. The diameter of the tube with the application of potash waste water (SSR400 solution) at the rate of 2 and 1 Lit/m2 was 4.99 and 4.11 cm, respectively. Application of Pseudomonas fluorescens and potash waste water (SSR400 solution) in 1/3 soil saturation at 96.4% and 94.4% at particles larger than 0.84 mm, respectively.
Discussion and Conclusion: The results showed that bacteria that have a high ability to hydrolyze urea and calcium carbonate precipitate, can play an effective role in increasing soil firmness. The compounds of calcium and magnesium chloride and calcium nitrate in the potash waste water (SSR400 solution) increase the adhesion of soil particles and soil stabilization. These solution increase the surface tension of the soil and strengthen the bond between soil particles. The calcium ion in potash waste water (SSR400 solution) has an effective role in softening soil colloids and reducing erosion. Overall, the results of qualitative urea hydrolysis test showed that Sporosarcina pasteurii had a high ability in hydrolysis of urea and traits related to biological stabilization of sand dunes. Pseudomonas fluorescens also showed less of these abilities. Waste water (SSR400 solution) as a mineral mulch also showed a good ability to stabilize sand dunes. However, it should be noted that very high salinity of this solution can cause many problems in desert lands. Therefore, it is necessary to reduce its salinity before recommending this solution as mulch. Also, increasing the volume of mulch application per square meter improved the stabilization properties of sand dunes. As the application of 1/3 soil saturation in all mulch increased stabilization. However, it should be noted that due to the limitations of the use of mulches in desert lands, including water and transportation of these solutions in desert areas, according to the results of this study, by using a less amount of selected mulch, acceptable results can be obtained in improving soil erosion properties.
     
Type of Study: Research | Subject: Wind erosion
Received: 2020/12/16 | Accepted: 2021/03/7

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