长期不同施肥下塿土有机碳和全氮在团聚体中的分布

【目的】研究小麦/玉米轮作体系不同施肥方式下土壤有机碳(SOC)和全氮(TN)在(?)土不同水稳性团聚体中的分布特征,以期深入理解不同施肥方式对土壤碳、氮固持的机制。【方法】采集(?)土21年长期肥料定位试验不同施肥处理0-10 cm和10-20 cm土层土样,分析其水稳性团聚体(2 mm、2~1 mm、1~0.5 mm、0.5~0.25 mm以及0.25 mm)有机碳和全氮的分布特征。试验设不施肥(CK),化肥氮磷钾配施(N、NP、NK、PK、NPK)和秸秆还田配施氮磷钾(SNPK)以及两个水平有机肥与氮磷钾配施(M1NPK、M2NPK)9个处理。【结果】长期施肥0-10 cm土层土壤团聚体SOC和TN含量明显高于10-20 cm,平均增幅20%以上。2~1 mm或1~0.5mm团聚体中SOC和TN的含量最高,0.25 mm团聚体最低。长期不施磷肥处理的土壤团聚体SOC和TN含量均与CK相似。NP、NPK以及SNPK处理,0-10 cm土层SOC较CK分别增加16%~43%、9%~40%和22%~47%;TN增幅分别为28%~48%、39%~61%和39%~91%。10 20 cm土层,NP、NPK以及SNPK处理2mm、2~1 mm、1~0.5 mm土壤团聚体SOC较CK增幅分别为35%~49%、17%~40%和45%~46%,TN增幅分别为44%~47%、39%~54%和54%~64%。长期有机肥与氮磷钾配施处理(M1NPK、M2NPK),0-10 cm土层的团聚体SOC平均较CK分别增加68%~122%和61%~163%,TN平均分别增加84%~133%和97%~175%;10-20 cm土层,SOC较CK平均增幅分别为20%~61%和39%~118%,TN增幅平均分别为43%~86%和107%~136%。SOC和TN主要储存于0.25 mm团聚体中(40%)2~1 mm团聚体储存最少(10%)。长期不施氮或不施磷对SOC和TN在团聚体中的储存比例基本没有影响。长期NP、NPK以及M1NPK、M2NPK均降低了各土层SOC和TN在2 mm或2~1 mm的储存比例增加了在1~0.25 mm团聚体储存比例。2 mm或2~1 mm团聚体的C/N比值高于微团聚体(0.25 mm),而与CK相比,长期施肥降低了土壤团聚体的C/N比值。【结论】关中地区(?)土长期偏施化肥对有机碳和全氮在团聚体的含量及分布没有显著影响而长期氮磷或氮磷钾化肥配合、氮磷钾与有机物配合均明显增加土壤团聚体的有机碳及全氮含量,特别是长期氮磷钾配合有机肥能显著增加土壤1~0.25 mm团聚体对土壤有机碳和全氮的固存比例,提高土壤有机碳和全氮储量减少温室气体的排放。

Distribution of soil organic carbon and nitrogen in water-stable aggregates of anurial loess soils under long-term various fertilization regimes

【Objectives】 Study on the distribution of soil organic carbon and nitrogen in different sizes of water-stable aggregates as affected by long-term various fertilization modes, will deepen the understanding of the soil carbon sequestration and nitrogen fixation.【Methods】Based on a long-term fertilization experiment in Eum-Orthic Anthrosols in Yangling City, Shaanxi Province, soil samples of 0-10 cm and 10-20 cm horizons were collected from the 9 different fertilization treatments[CK, N, NP, NK, PK, NPK, straw returning + NPK (SNPK), suitable manure + NPK (M1NPK), high manure input + NPK (M2NPK)]. Soil organic carbon and total nitrogen contents in water-stable aggregates of 2 mm, 2-1 mm, 1-0.5 mm,0.5-0.25 mm and 0.25 mm were analyzed. 【Results】 The SOC and TN contents in 0-10 cm soil lager are 20% significantly higher than in 10-20 cm soil layer. The highest SOC and TN contents are in the aggregates of 2-1 mm and /or 1-0.5 mm sizes, the lowest in aggregates of 0.25 mm size. The SOC and TN contents in N, NK and PK treatments are similar to those in CK. The NP, NPK and SNPK treatments significantly increase the SOC and TN contents in the two soil layers compared to CK. In 0-10 cm soil layer of above corresponding treatments, the SOC contents increased by 16%-43%, 9%-40% and 22%-47%, and the TN contents by 28%-48%, 39%-61% and 39%-91%, respectively. In 10-20 cm soil layer, the SOC contents are increased by 35%-49%, 17%-40% and 45%-46%, and the TN contents by 44%-47%, 39%-54% and 54%-64%, respectively. The long term application of manure plus NPK treatments (M1NPK and M2NPK) cause significant increase of SOC and TN contents in all size of aggregates. The increments of SOC in 0 -10 cm are from 68% to 122% and from 61% to 163%,and those of TN contents are from 84% to 133% and from 97% to 175%, respectively, and in 10-20 cm layer the increments of SOC are from 20% to 61% and from 39% to 118% and the TN contents are from 43% to 86% and from 107% to 136%, respectively. More than 40% of SOC and TN contents are distributed in aggregates 0.25 mm size fraction, less than 10% in 2-1 mm size. The treatments of NP and NPK with or without organic amendments show significant lower proportions of SOC and TN in large aggregates ( 2 mm or 2-1 mm), and higher proportions in small aggregates (1-0.25 mm) in 0-20 cm layers. The C/N ratios show no consistent trend in aggregates. However, C/N ratios in aggregates in the fertilizer treatments are lower than that in CK after the long term fertilization. 【Conclusions】 The combined application of NP or NPK fertilizers without or with organic amendments significantly increase SOC in all aggregates in 0-10 cm soil layer. The MNPK treatment significantly increases SOC partitioning in 1-0.25 mm of aggregates, and consequently not only increases SOC storage but also conserves high TN in the soil.