چكيده لاتين :
Introduction: Organic matter is considered as the main element for soil fertility by improving the condition of agglomeration, porosity and soil permeability. One of the most useful ways to use plant debris is to turn it into Biochar and Hydrochar. Biochar is a kind of coal produced from plant biomass and agricultural waste that is burned in the presence of low oxygen content or its absence. The hydrothermal process involves heating the biomass or other materials in a pressurized in the presence of water at a temperature between 180 and 250 C, and the result of this reaction is coal (Hydrochar) and soluble organic matter. Biochar and Hydrochar have several advantages such as climate change mitigation through carbon sequestration, soil cation exchange capacity (CEC) increasing, soil fertility, plant growth and root development, improved soil structure and stability, increased soil moisture storage capacity and soil pH adjustment. Coarse soils have large pores and they have low ability to absorb the water and nutrient. The aim of this research was to determine the optimum temperature of wheat straw Biochar and Hydrochar production, and to investigate the effect of these materials on bulk density, total porosity and moisture curve of Sandy Loam soil.
Materials and Methods: In order to produce biochar, at first the wheat straw was washed and dried in the oven. Then it was grinded and was made at different temperatures (200 to 600 ̊ C) inside a furnace for four hours. Similar to biochar, for producing hydrochar, after washing and drying the wheat straw it was grinded into particles ranges from 0.5 to 1 mm. Then it was placed in a stainless steel autoclave with deionized water. The autoclave was heated at different temperatures between 140-230 ̊ C for four hours. The optimum temperature for producing of biochar and hydro-char was determined by using stable organic matter yield index (SOMYI), and it was used in this study. The pH and EC of the biochar and hydro-char samples were measured by combining 1 g of a sample with 20 mL DI water. The cationic and anionic exchange capacity were determined by replacing sodium nitrate with hydrochloric and potassium chloride (Chintala et al., 2013). Surface area was obtained using methylene blue method. A CHNSO Elemental Analyzer (Vario ELIII- elementar- made in Germany) was used to determine the content of C, N, H, S and O in the samples. Potassium and sodium content were measured by flame photometer and calcium and magnesium were measured by titration with EDTA. Biohchar and hydrochar treatments were applied at three levels of 2, 5 and 10 mg / kg soil in three replications in 21 lysimeter. The bulk density, total porosity and moisture curve of soil were measured after four-month irrigation period.
Results and Discussion: According to the calculated value of stable organic matter yield index (SOMYI) at various temperatures in this study, the maximum thermal constancy of wheat straw biochar was 16.20 at temperature of 300 ̊ C and for hydro-char was obtained as 6.13 at the temperature of 200 ̊ C. So, the temperatures of 300 and 200 ̊C were determined as the optimum temperature of sustainable carbon biochar and hydro-char production and were used to continue the experiments of this study. The results showed that addition of HW2, HW5, HW10, BW2, BW5 and BW10 to soil compared to control treatment significantly decreased the bulk density of the soil, 8.97, 11.77, 15.17, 7.9, 10 and 13.10 percent respectively. Also, results showed that addition of HW2, HW5, HW10, BW2, BW5 and BW10 to the soil as compared to control treatment increased soil porosity by 8.8, 11.48, 15.77, 6.48, 9 and 22.13 percent, respectively. The reason for reducing the soil bulk density and increasing the total porosity of soil can be due to the mixing of the soil with materials with a lower bulk density and the effect of increasing the organic matter of the soil due to the use of Biochar and Hydrochar. Based on statistical analysis, wheat straw Biochar and Hydrochar had a significant effect (P <0.05) on moisture content in different suction of soil. The results showed that addition of HW2, HW5, HW10, BW2, BW5 and BW10 to soil as compared to control treatment increased available soil moisture content by 24.11, 43.61, 78.88, 16.34, 34.30 and 74.69 percent respectively. Organic matter affects the structure of soil pores that determines the extent of moisture storage in the soil. For example, intrinsic porosity leads to the formation of fine pores in the soil, thereby it increases soil moisture retention capacity. Comparison of Biochar and Hydrochar treatments showed that Hydrochar has more potential to decrease soil bulk density, increase total porosity and soil moisture content.
Conclusions: In general, it can be concluded that the addition of wheat straw Biochar and Hydrochar samples cause positive changes in some physical properties of the soil such as bulk density, total porosity and soil moisture content in different suction. Given that Biochar and Hydrochar are a carbon source, since carbon is highly porous and has high nutrient and moisture content retaining power. As a result, the use of Biochar and Hydrochar to improve soil properties can play a fundamental role. The results showed that the Biochar and Hydrochar treatments in the amount of 10 and 2 grams per kilogram of soil had the highest and the least effect on the studied properties of the soil, respectively.
