玉米秸秆生物炭及其老化对石灰性农田土壤氨挥发的影响

为探明玉米秸秆粉末、新鲜和老化(自然老化、高温老化、冻融循环老化)玉米秸秆生物炭对黄土高原石灰性农田土壤氨挥发的影响,将不同材料按2%(质量比)与土壤充分混匀,开展为期29 d的室内静态土壤培养实验,研究土壤氨挥发速率的日变化以及整个培养期间的氨挥发累积量。同时,为探究不同材料对土壤氨挥发影响的机理,测定了培养初态和终态土壤样品的无机氮含量、氨氧化速率和氨氧化细菌数量,并研究了不同材料对水中NH_4~+-N的吸附特性。结果表明,在整个培养过程中,与未添加外源材料处理相比,添加冻融循环老化生物炭或高温老化生物炭处理的氨挥发累积量减少了30%,添加自然老化生物炭或新鲜生物炭处理的氨挥发累积量减少了23%,添加玉米秸秆粉末处理的氨挥发累积量减少了19%。施氮肥后1~10 d为土壤氨挥发的主要阶段,该阶段氨挥发累积量占整个培养过程氨挥发累积量的90%以上。不同材料对土壤氨挥发影响的机理研究表明,冻融循环老化生物炭和高温老化生物炭较强的氨挥发抑制作用与其较强的土壤氨氧化促进作用以及NH_4~+-N吸附能力有关。本研究有助于深刻理解新鲜和老化玉米秸秆生物炭还田对石灰性农田土壤氨挥发的影响,为降低土壤氨挥发提供有效途径,为生物炭在黄土高原的农业工程应用提供理论借鉴。

Effects of fresh and aged maize straw-derived biochars on ammonia volatilization in a calcareous arable soil

The object of this study was to examine the effects of maize-straw powder, fresh and aged maize straw-derived biochars (including spontaneous aging, high-temperature aging, and freeze-thaw cycles aging) on ammonia (NH₃) volatilization in a typical Loess Plateau calcareous arable soil. The indoor static soil incubation experiment of 29 days was carried out after adding and evenly mixing 2% (in mass) of abovementioned materials into and with the soil sample to investigate the diurnal variation of soil NH₃ volatilization rate and the cumulative NH₃ volatilization of the soils during the whole incubation period. To unravel the mechanisms that control NH₃ volatilization from the soil amended with different materials, the inorganic nitrogen content, ammonia oxidation rate, and ammonia-oxidizing bacteria amount of the soils were determined at the beginning and the end of incubation. Moreover, the NH₄⁺-N adsorption characteristics of the materials were studied. The results indicated that all the materials inhibited NH₃ volatilization of the calcareous arable soil. Compared with the soil without exogenous material added, the cumulative NH₃ volatilization during the whole incubation period decreased by 30% in the freeze-thaw cycles aged or high-temperature aged biochar amended soil, decreased by 23% in the spontaneous aged or fresh biochar amended soil, and decreased by 19% in the maize-straw powder amended soil. The first 10 days after nitrogen fertilizer application was the main stage of NH₃ volatilization, which accounted for more than 90% of the cumulative NH₃ volatilization. The relatively stronger NH₃ volatilization inhibition abilities of freeze-thaw cycles aged and high-temperature aged biochars were mainly attributed to their stronger abilities of ammonia oxidation promotion and NH₄⁺-N adsorption. This study will be helpful for understanding the effects of returning fresh and aged maize straw-derived biochars back to farmland on soil NH₃ volatilization. Moreover, the study will supply an effective way to reduce soil NH₃ volatilization, and will provide a theoretical reference for the agricultural application of biochar in arable soils of the Loess Plateau.