施肥和土层置换对深层土壤秸秆碳固定与残留的影响

Effects of Fertilization and Translocation Treatments on Sequestration and Retention of Straw Carbon in Deep Soil

深层土壤指深度大于20 cm土层的土壤。一般情况下,深层土壤有机碳(SOC)储量占1 m深土体有机碳总储量的一半以上,对土壤碳固定和土壤肥力的发挥起着重要作用。然而关于深层土壤有机碳的固定机制还不很明确。本研究以沈阳农业大学长期定位试验站不同施肥处理的土壤(40~60 cm)为研究对象,用土壤添加13C标记秸秆后设置原位(40~60 cm)与土层置换(0~20 cm)的田间培养试验方法,量化秸秆碳对土壤总有机碳的相对贡献率,分析秸秆碳在土壤中的残留动态,明确不同施肥处理和土层置换对秸秆碳在深层土壤中固定的影响,以期为深层土壤有机碳固定和土壤培肥提供依据。结果表明:在整个培养时期(150 d),原位培养SOC中秸秆碳的贡献率(fm)和秸秆碳残留率(Rmaize)平均值分别为32.62%和44.86%,土层置换fm和Rmaize平均值分别为30.23%和40.09%。第150 d与第30 d相比,原位培养fm和Rmaize分别降低4.15%和8.33%,土层置换fm和Rmaize分别降低1.86%和3.36%。无论土层置换与否,不施肥(CK)处理的fm和Rmaize平均值分别高于施肥(N4和M2N2)处理3.83%和3.08%。以上结果表明,深层土壤秸秆碳的固定与残留受施肥和外界环境的影响,不施肥处理有利于秸秆碳在深层土壤的固定。

Deep soil refers to soil layer>20 cm depth.In general,more than half of soil organic carbon(SOC)was stored in deep soil within 1 m depths,which plays an important role in soil C sequestration,crop productivity and soil fertility.Little was known,however,about the sequestration of SOC in deep soil layers.Based on the long-term experiment of Brown Earth in Shenyang Agricultural University,the deep soil(40-60 cm)was added with13 C labeled maize straw under different fertilization treatments,and then placed at 40-60 cm(in-situ)and 0-20 cm(translocation)depths for incubation.We quantified the relative contribution of straw C to total SOC,analyzed the retention dynamics of straw C in soil and investigated the effects of different fertilization and translocation treatments on straw C sequestration in soil,in order to provide a reference for soil fertility improvement and deep soil C sequestration.The results showed that the average values of contribution percentage of straw C to SOC(fm)and the residual percentage of straw C(Rmaize)in soil were 32.62%and 44.86%in in-situ treatments,and were 30.23%and40.09%under translocation treatments,respectively.The value of fmand Rmaizewere 4.15%and 8.33%lower on the150 thday than those on the 30 thday under in-situ treatments,and were 1.86%and 3.36%lower on the 150 thday than those on the 30 thday under translocation treatments,respectively.Whether in-situ or translocation incubation,the average value of fmand Rmaizein the no-fertilization(CK)treatment were 3.83%and 3.08%higher than those in the fertilization(N4 and M2 N2)treatments,respectively.The above results indicated that the retention and sequestration of straw C in deep soil were affected by fertilization and external environment and no fertilization was beneficial to the sequestration of straw C in deep soil.