棉秆炭老化特性及其对风沙土氨挥发的影响

Features of aged cotton stalk charcoal and its effect on ammonia volatilization from sand soil

【目的】研究干湿交替、冻融循环、柠檬酸老化棉花秸秆生物炭特性,分析老化棉秆炭对风沙土氨挥发的影响,为干旱区棉花秸秆生物炭利用及其对土壤改良的长期效应提供理论依据。【方法】以棉花秸秆生物炭为试材,设置干湿交替、冻融循环、柠檬酸3种老化试验,分析老化前后棉秆炭的表面形貌、比表面积和孔径、pH值、电导率等理化性质;设置室内静态土壤培养试验,研究老化棉秆炭对土壤氨挥发速率以及氨挥发累积量的影响。【结果】(1)与新鲜棉秆炭相比,老化棉秆炭的pH值、电导率、全磷、全钾含量均降低,且柠檬酸老化棉秆炭比干湿交替、冻融循环老化棉秆炭下降程度大;柠檬酸老化棉秆炭比表面积、总孔体积和介孔体积显著增加1.88倍、1.37倍和1.36倍,平均孔径减小0.19倍(P>0.05),干湿交替和冻融循环老化棉秆炭比表面积显著减小,但平均孔径显著增大;(2)与新鲜棉秆炭处理相比,添加各老化棉秆炭处理的氨挥发累积量减少了7.4%~34.7%。【结论】冻融循环、干湿交替、柠檬酸3种老化方式改变棉秆炭特性,抑制风沙土中氨的挥发,有利于土壤氮素的固定,柠檬酸老化棉秆炭对土壤氨挥发抑制效果最好。

【Objective】To study on the characteristics of biochar from cotton straw aged with dry-wet alternation,freeze-thaw cycle,citric acid,and explore the effects of aging cotton stalk charcoal on ammonia volatilization from sand soil with a view to providing theoretical basis for the utilization of cotton stalk charcoal and its long-term effects on soil improvement in arid areas.【Methods】Cotton straw biochar was taken as the test material,three aging methods of dry and wet alternation,freezing and thaw cycle and citric acid were set to analyze the surface morphology of cotton straw carbon and analyze the surface morphology,specific surface area and pore size,pH value,electrical conductivity and other physical and chemical properties of cotton stalk charcoal before and after aging.Meanwhile,the effects of aged cotton stalk charcoal on ammonia volatilization rate and ammonia volatilization accumulation in soil were studied by indoor static soil culture experiment.【Results】(1)Compared with fresh cotton stalk charcoal,the pH value,electrical conductivity,total phosphorus and total potassium contents of aged cotton stalk charcoal all decreased and its degree of citric acid was greater than those of dry-wet alternation and freeze-thaw cycle.The specific surface area,total pore volume and mesoporous volume of citric acid of aged cotton stalk charcoal increased by 1.88,1.37 and 1.36 folds,respectively and the average pore size decreased by 0.19 times(P>0.05).The specific surface area of dry-wet and freeze-thaw aged cotton stalk charcoal decreased significantly,but the average pore size increased significantly.(2)In the whole culture process,the cumulative amount of ammonia volatilization was reduced by 7.4%~34.7%compared with the treatment of fresh cotton stalk charcoal.【Conclusion】Three aging modes of freeze-thaw cycle,alternation of wetting and drying,and citric acid change the characteristics of cotton stalk charcoal,inhibit ammonia volatilization in aeolic soil,which is beneficial to soil nitrogen fixation.The citric acid aged cotton stalk charcoal has the best inhibition effect on ammonia volatilization in soil.