تاثیرات زغال زیستی و زئوپلانت برروی ویژگی‌های فیزیکی و مکانیکی خاک‌های فرسایش‌پذیر (مطالعه موردی: بستان)

فرسایش بادی یکی از مهترین معضلات زیست محیطی در مناطق خشک و نیمه خشک است که سبب هدررفت خاک و تولید گرد و غبار می گردد. در این پژوهش تاثیرات زغال زیستی باگاس نیشکر، کنوکارپوس و تیمار آلیمعدنی زئوپلانت در سه سطح (0، 2 و 4 درصد وزنی)، دو سطح رطوبتی (25 و 50 درصد ظرفیت زراعی) و در 3 تکرار به صورت فاکتوریل در قالب طرح کاملا تصادفی بر روی ویژگی‌های فیزیکی و مکانیکی خاک به عنوان شاخص هایی از فرسایش‌پذیری، بررسی شد. نمونه خاک از محدوده تالاب هورالعظیم به عنوان یکی از کانون های گردوغبار جمع‌آوری و پس از اعمال تیمارها، به مدت 90 روز در سینی هایی به ابعاد (10 × 30 × 70 سانتی متر) انکوباسیون گردید. پس از اتمام انکوباسیون سینی ها درون تونل باد قرار داده شد و تحت تاثیر وزش باد با سرعت 15 متر بر ثانیه در ارتفاع 2 متری از سطح خاک قرار گرفتند. مهمترین پارامترهای فیزیکی و مکانیکی اندازه‌گیری شده شامل پایداری خاکدانه، مقاومت فروروی، مقاومت کششی، شاخص تردی خاکدانه، مقاومت برشی، شاخص سله، شاخص بافت خاک و درصد ماده آلی بودند. نتایج نشان داد که هر سه تیمار در دو سطح رطوبتی، به طور معنی داری سبب افزایش تخلخل، مقاومت کششی و کاهش شاخص سله در مقایسه با نمونه بدون تیمار شدند (p <0.01). همچنین زغال زیستی باگاس نیشکر و زئوپلانت (سطح 2 درصد) به طور معنی داری مقاومت برشی را افزایش، در حالی‌که زغال زیستی کنوکارپوس اثر معنی داری بر مقاومت برشی نداشت. در مجموع تیمارهای مورد استفاده با ایجاد لایه محافظ (armoring effect) در سطح خاک و نیز افزایش پایداری خاکدانه‌ها، منجر به کاهش فرسایش شدند.

Effects of Biochar and Zeoplant on Physical and Mechanical Properties of Erodible Soils (Case Study: Bostan)

Introduction: Wind erosion is one of the most important environmental challenges in arid and semiarid regions which cause soil loss and dust storm. In recent decades, the potential of soil erosion has been recognized as serious threat against soil sustainability. In addition, accelerated soil erosion has led to harmful environmental effects. Therefore, focus on soil erosion outcomes is necessary in order to mitigate its environmental impacts. Understanding interactions between land use management and topographical properties of landscape are important in order to effectively control soil erosion through implementing best management practices (BMPs). Application of mulch is one of the most prevailing scenarios to prevent the erosive soil against wind as an erosive factor in the hotspots. In this regard the type of much is really important because the environmental aspects and the mulch consistency are important factors for production and selection of mulch between several options. Nowadays, sustainable management is one of the most important scopes in order to achieve the aims of human healthy. In this regards the Bagasse of sugarcane and Conocarpus were selected as feedstocks to produce biochars. Biochar is the byproduct of anaerobic process which called pyrolysis. The biogases, energy and so on are other outputs of pyrolysis. Another treatment which evaluated in this study was Zeoplant. Zeoplant is a super absorptive material which is able to hold the water in the soil therefore is capable to enhance the water holding capacity of the soil. ;Materials and Methods: In this study the effects of biochar of Bagasse from sugarcane, biochar of Conocarpus and Zeoplant in three levels (0, 2 and 4 percentage) and two moisture levels (25 and 50 percentage of FC) and 3 replications in randomized completely design with factorial on physical and mechanical properties of soil as indices of soil erodibility was studied. Soil sampling accomplished from Horalazim marshes and after application of treatment, incubated in tray with the size of 70×30×10 cm for 90 days. After incubations the trays located in wind tunnel in order to simulate wind erosion process under a wind with 15 m/sec speed and 2 m from soil surface. The main measured soil physical and mechanical parameters include mean weight diameter (MWD), penetration resistance (PR), tensile strength (TS), friability index (FI), shear strength, crusting index (CI), soil textural index and organic matter. The statistical analysis was performed using SAS 9.2 software and the mean comparison was accomplished with Duncan test (5 %). In order to draw the graphs Origin 2017 software was used. ;Results and Discussion: The soil texture was silty loam (SiL) including 62% silt, 26% clay and 12% sand, therefore the soil was sensitive to wind erosion. Soil organic matter before application of biochars and Zeoplant was around 1.93% and after application increased to 3.78%. Application of these treatments and the period of incubation, enhanced the soil porosity. Generally increasing soil organic matter and soil porosity and decreasing of bulk density are the main factors to increase the soil aggregation. Our results showed that all three treatments in two moisture levels significantly increased soil porosity, tensile strength and field capacity and decrease soil crusting index (P <0.01). Biochar of bagasse and Zeoplant (2%) also significantly increased shear strength whereas biochar of Conocarpus has no significant effect on shear strength. Overall the applied treatments with armoring effect (AE) and increase the soil aggregate stability, diminished the wind erosion.;Conclusion: Our study illustrated that application of biochar is able to improve soil physical and mechanical properties. The main aspect of this positive effect is the specific characteristics and the structure of biochar which showed with SEM (Scanning electronic microscope) images. Moreover, Zeoplant is organicinorganic treatment and including high potential to absorb the water in the soil. Indeed, the mulching is an effective management strategy to maintain and preserve the soil against wind (as erosive agent) however afterwards a vegetation cover must be grow on the surface. Therefore some treatments such as Zeoplant are essential to hold the water in the soils of arid and semiarid regions because in those areas the water scarcity is one of the main challenges. Based on our results and evaluation of these treatments we found two main processes which are effective to mitigate wind erosion. The first is aggregation process because of organic carbon and organic matter in the soil and the binding between organic and inorganic components. The second one is an armoring effect which is originating from amendments especially biochar lumps on the surface. Finally our results confirmed the application of evaluated treatments to preserve the erosive soil against wind.