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Abstract:  
Introduction: Salinity is one of the most important environmental stresses that affectes on plant growth. In saline soils, plants influenced by some toxic ions and decrease of water availability. Crop residues are one of the major organic wastes in agriculture that can useful for soil and plant. Organic matter has positive effects on the soil physical and chemical properties. Converting agricultural wastes to biochar is a good way to achieve valuable amendment. Biochar is a carbon-rich product obtained by heating a biomass in an oxygen-free chamber. It can be used for carbon sequestration by applying large amounts of carbon and this material is resistant to decomposition. Biochar is highly persistent in soil, and evidence shows that Biochar has stored atmospheric carbon for hundreds to millions of years. The use of Biochar has been shown to increase water holding capacity, microbial activity and nutrient availability in soil. However, its effect on soil properties depends on quantity of application and source of biochar. The effects of biochar on saline soils depend on its properties which has received less attention. This study was conducted to investigate the effect of biochar of date palm trees foliage on the physical and chemical properties of a saline soil.
 Materials and Methods: In this research biochar was prepared from date palm trees foliage wastes in 500°C with limited oxygen conditions. This experiment was conducted in a completely randomized design with three replications. Biochar at rates of 0, 0.5, 1, 1.5 and 2% were mixed with saline soils and incubated with humidity at field capacity for 90 days. After this time samples were air dried and some soil physicochemical characteristics were determined. Comparison of the means was performed using Duncanchr('39')s test at a confidence level of 95%.
Results: The results showed that use of biochar of date foliage in soil, significantly increased soil chemical properties such as electrical conductivity (EC), organic carbon, calcium, Magnesium, sodium and potassium while decreased sodium adsorption ratio (SAR) and sodium to potassium ratio. Biochar addition to soil increased porosity by 10% and reduced bulk density by 4%. Treatments did not have a significant effect on pH, available phosphorus, field capacity and soil particle density. Addition of 2% biochar increased the concentration of calcium in soil by 2.08 times compared to the control. Soil magnesium changes are similar to calcium. The concentration of magnesium increased compared to the control (2.88 times more than the control treatment) by increase in use of date biochar in soil. Results indicated that concentration of available potassium in soil increased significantly by application of different levels of biochar. With increasing the amount of bio-dates in 1.5 and 2% treatments, the amount of potassium increased about 12.33 and 18.79 times, respectively, compared to the control. The highest increase in sodium was related to the application of 2% date biochar, which was 49.35% more than the control. Finally using 2% biochar reduced sodium adsorption ratio by 7.6%.
Discussion and Conclusion: This study showed that use of biochar of date palm trees improved some parameters of saline soil such as SAR, organic matter and some nutrients. Increase in EC is due to increase of sodium as a destructive factor and other cations such as calcium, magnesium and potassium as useful plant nutrients. On the other hand, sodium to potassium ratio decreased. This study showed that increase in potassium was more than sodium and improved this index. Biochar has increased porosity due to its high specific surface area. The use of 2% biochar treatment led to increase in amount of organic carbon in saline soil by about three times. Due to the low specific gravity of biochar, it can be expected that soil density decreased by application of biochar in soil. However, the increase in biochar did not have a significant effect on the soil particle density. This is probably due to the low weight of biochar particles versus the high weight of minerals in the soil and also the amount of biochar consumed. It seems that application of biochar as an amendment can improve saline soil properties. It seems that the size of biochar particles may have a different effect on changing soil properties, which can be investigated in future research.
     
Type of Study: Research | Subject: Desert
Received: 2020/08/23 | Accepted: 2021/03/1

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