不同施肥下根际沉积对秸秆碳氮在土壤剖面中固存的影响

doi:10.3864/j.issn.0578-1752.2023.19.012

摘要/Abstract

摘要：

【目的】秸秆还田是我国东北黑土地保护的重要措施。在实际的农业生产中秸秆与根际沉积同时存在，然而关于它们同时存在时秸秆碳氮在土壤中的固定特征仍不清楚。本研究旨在比较不同土层土壤有机碳（SOC）中秸秆碳（¹³C-SOC）和土壤全氮（TN）中秸秆氮（¹⁵N-TN）含量的差异，探讨不同施肥下根际沉积对秸秆碳氮在土壤中固存的影响，以期为东北黑土地的保护和利用提供依据。【方法】以沈阳农业大学长期定位试验站不同施肥处理（不施肥，CK；单施化肥，NP）为研究对象，分别仅添加¹³C¹⁵N双标记秸秆（S）和添加¹³C¹⁵N双标记秸秆结合根际沉积（以下简称“根际沉积”）（SR），即设CK+S、CK+SR、NP+S和NP+SR 4 个处理。分别在田间原位试验的第50天和第150天采样，并测定不同土层SOC含量及其δ¹³C值、TN含量及其δ¹⁵N值。【结果】在秸秆分解前期（第50天），施肥、根际沉积及其交互作用显著影响（P<0.05）表层（0—20 cm）土壤的¹³C-SOC和¹⁵N-TN含量。第50天，CK+SR与CK+S处理相比，表层土壤的¹³C-SOC和¹⁵N-TN含量分别增加了18.6%和21.7%（P<0.05）；不同施肥下，S（CK+S和NP+S）与SR（CK+SR和NP+SR）处理表层土壤¹³C-SOC对SOC的贡献率平均分别为10.5%和12.0%；CK下两个处理（CK+S和CK+SR）与NP下对应的处理（NP+S和NP+SR）相比，表层土壤¹⁵N-TN对TN的贡献率平均增加了27.6%（P<0.05）。第50天，深层土壤（20—50 cm）¹³C-SOC对SOC的贡献率和¹⁵N-TN对TN的贡献率分别为1.0%—2.2%和0.5%—0.9%。在秸秆分解后期（第150天），根际沉积和施肥分别显著影响（P<0.05）表层土壤¹³C-SOC和¹⁵N-TN含量。第150天，仅添加秸秆处理与根际沉积处理相比，表层土壤¹³C-SOC含量增加了12.6%（P<0.05）；CK下两个处理与NP下对应的处理相比，表层土壤¹⁵N-TN含量平均增加了22.0%（P<0.05）；CK各处理和NP各处理表层土壤¹⁵N-TN对TN的贡献率平均分别为5.5%和4.0%。第150天，深层土壤¹³C-SOC对SOC的贡献率和¹⁵N-TN对TN的贡献率分别为0.8%—3.2%和0.7%—1.8%。【结论】秸秆分解后期根际沉积对表层土壤中秸秆碳的固定起负反馈效应，秸秆碳氮不断从表层土壤向深层土壤迁移和累积，其对土壤有机碳和氮库稳定性的影响应予以重视。

关键词: 根际沉积, 秸秆碳, 秸秆氮, ¹³C¹⁵N双标记, 黑土

Abstract:

【Objective】Straw returning is an important measure for protecting black soil in Northeast China. Straw and rhizodeposition coexisted in the practical agricultural production, while the sequestration characteristics of straw carbon (C) and nitrogen (N) in soils remained not very clear under this condition. The purpose of this study was to compare the differences in the content of soil organic C (SOC) derived from straw C (¹³C-SOC) and that of soil total N (TN) derived from straw N (¹⁵N-TN) among different soil layers, and to investigate the effects of rhizodeposition on straw C and N sequestration in soil profile under different fertilization conditions, so as to provide a basis for the protection and utilization of black soil in Northeast China. 【Method】Based on the long-term experimental station of Shenyang Agricultural University, the treatments of adding ¹³C¹⁵N double-labeled straw (S) and its combination with rhizodeposition (hereafter referred to as “rhizodeposition”) (SR) were designed under different fertilization plots (no fertilization, CK; single application of chemical fertilizer, NP), including four treatments: CK+S, CK+SR, NP+S, NP+SR. The contents of SOC and TN, and values of δ¹³C and δ¹⁵N at different soil layers were measured after the 50 and 150 days of in-situ experiment. 【Result】At the early stage of straw decomposition (the 50^th day), fertilization, rhizodeposition and their interactions significantly affected (P<0.05) the contents of ¹³C-SOC and ¹⁵N-TN in the topsoil (0-20 cm). On the 50^th day, compared with the CK+S treatment, the CK+SR treatment increased the contents of ¹³C-SOC and ¹⁵N-TN in the topsoil by 18.6% and 21.7% (P<0.05), respectively. The contribution percentage of ¹³C-SOC to SOC in the topsoil was, on average, 10.5% and 12.0% in the S (CK+S and NP+S) and SR (CK+SR and NP+SR) treatments under different fertilization, respectively. The contribution percentage of ¹⁵N-TN to TN in the topsoil was, on average, higher 27.6% (P<0.05) in the two treatments under CK (CK+S and CK+SR) than that in the corresponding treatments under NP (NP+S and NP+SR). On the 50^th day, the contribution percentage of ¹³C-SOC to SOC and that of ¹⁵N-TN to TN at deep soil (20-50 cm) were 1.0%-2.2% and 0.5%-0.9%, respectively. At the later stage of straw decomposition (the 150^th day), rhizodeposition and fertilization significantly affected (P<0.05) the contents of ¹³C-SOC and ¹⁵N-TN in the topsoil, respectively. On the 150^th day, compared with the treatment of rhizodeposition, the treatment of straw addition increased the ¹³C-SOC content in the topsoil, on average, by 12.6% (P<0.05). The ¹⁵N-TN content in the topsoil was, on average, higher 22.0% (P<0.05) in the two treatments under CK than that in the corresponding treatments under NP. The contribution percentage of ¹⁵N-TN to TN in the topsoil in CK and NP treatments was 5.5% and 4.0%, respectively. On the 150^th day, the contribution percentage of ¹³C-SOC to SOC and that of ¹⁵N-TN to TN at deep soil were 0.8%-3.2% and 0.7%-1.8%, respectively. 【Conclusion】Rhizodeposition had a negative feedback effect on the sequestration of straw C in topsoil during the later stage of straw decomposition. Straw derived C and N were constantly migrated and then accumulated from topsoil to deep soil, and their influences on the stabilities of soil organic C and N pools should be paid more attention.

Key words: rhizodeposition, straw carbon, straw nitrogen, ¹³C¹⁵N double-labelling, black soil

梅秀文, 祝腾霄, 李玉萍, 李双异, 孙良杰, 安婷婷, 汪景宽. 不同施肥下根际沉积对秸秆碳氮在土壤剖面中固存的影响[J]. 中国农业科学, 2023, 56(19): 3856-3868.

MEI XiuWen, ZHU TengXiao, LI YuPing, LI ShuangYi, SUN LiangJie, AN TingTing, WANG JingKuan. Effects of Rhizodeposition on Straw Carbon and Nitrogen Sequestration in Soil Profile Under Different Fertilization Conditions[J]. Scientia Agricultura Sinica, 2023, 56(19): 3856-3868.

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施肥处理 Fertilization treatment	土壤深度 Soil depth (cm)	土壤有机碳 Soil organic carbon (g·kg^-1)	δ¹³C值 δ¹³C value (‰)	全氮 Total nitrogen (g^.kg^-1)	δ¹⁵N值 δ¹⁵N value (‰)	碳氮比 C/N ratio	铵态氮 Ammonium nitrogen (mg·kg^-1)	硝态氮 Nitrate nitrogen (mg·kg^-1)	速效磷 Available phosphorus (mg·kg^-1)
CK	0—20	8.77±0.14Ab	-18.08±0.12Aa	1.09±0.01Ab	6.45±0.28Ab	8.02±0.10Aa	4.52±0.06Ab	9.81±0.04Ab	7.43±0.72Bb
	20—40	6.62±0.03Bb	-18.95±0.04Ba	0.83±0.02Bb	6.36±0.09Aa	8.00±0.21Aa	4.15±0.21Bb	5.56±0.24Bb	9.21±0.42Ab
	40—50	3.49±0.03Cb	-19.83±0.04Cb	0.61±0.02Cb	6.64±0.12Aa	5.79±0.12Bb	4.74±0.10Aa	2.20±0.18Cb	3.95±0.08Cb
NP	0—20	9.73±0.24Aa	-18.94±0.02Ab	1.33±0.06Aa	6.95±0.07Aa	7.62±0.08Ab	8.07±0.14Aa	71.23±1.42Aa	45.83±0.63Ba
	20—40	7.28±0.12Ba	-18.90±0.03Aa	1.18±0.01Ba	6.50±0.16Ba	6.19±0.11Bb	6.05±0.03Ba	58.99±1.03Ba	60.95±0.21Aa
	40—50	4.22±0.04Ca	-19.22±0.20Ba	0.68±0.00Ca	6.56±0.03Ba	6.25±0.04Ba	4.56±0.22Ca	18.65±0.47Ca	5.37±0.30Ca

因变量 Variance	因子 Factor	50 d			150 d
因变量 Variance	因子 Factor	0—20 cm	20—40 cm	40—50 cm	0—20 cm	20—40 cm	40—50 cm
SOC	施肥 Fertilization (F)	P<0.01	0.174	P<0.05	P<0.01	P<0.01	P<0.01
	根际沉积 Rhizodeposition (R)	0.167	P<0.05	0.083	0.337	P<0.01	P<0.01
	F×R	P<0.01	P<0.05	0.776	0.587	P<0.01	P<0.01
¹³C-SOC	施肥 Fertilization (F)	P<0.01	P<0.01	P<0.01	0.085	P<0.01	P<0.01
	根际沉积 Rhizodeposition (R)	P<0.01	0.354	P<0.05	P<0.01	P<0.01	P<0.05
	F×R	P<0.01	0.279	0.205	0.920	P<0.01	P<0.01
f_mc	施肥 Fertilization (F)	0.150	0.089	P<0.01	P<0.05	0.142	P<0.01
	根际沉积 Rhizodeposition (R)	P<0.01	0.127	P<0.05	P<0.01	0.359	P<0.01
	F×R	0.906	P<0.05	0.138	0.924	P<0.01	P<0.01
TN	施肥 Fertilization (F)	P<0.01	0.976	P<0.05	P<0.01	P<0.01	0.719
	根际沉积 Rhizodeposition (R)	0.866	0.188	0.449	0.865	0.153	P<0.01
	F×R	0.068	0.129	0.190	0.074	P<0.05	P<0.01
¹⁵N-TN	施肥 Fertilization (F)	P<0.01	P<0.01	P<0.05	P<0.01	P<0.01	0.081
	根际沉积 Rhizodeposition (R)	P<0.01	P<0.01	0.141	0.219	P<0.01	P<0.01
	F×R	P<0.01	P<0.01	P<0.05	0.113	P<0.01	0.347
f_mn	施肥 Fertilization (F)	P<0.01	P<0.01	0.189	P<0.01	0.115	P<0.05
	根际沉积 Rhizodeposition (R)	P<0.01	P<0.05	0.065	0.150	P<0.01	P<0.05
	F×R	P<0.01	P<0.01	P<0.01	0.516	P<0.01	P<0.05

处理 Treatment	秸秆碳的残留率 Residual percentage of straw carbon, R_mc (%)		秸秆氮的残留率 Residual percentage of straw nitrogen, R_mn (%)
处理 Treatment	50 d	150 d	50 d	150 d
CK+S	38.1±1.2c	44.6±0.4a	66.8±0.0d	88.4±2.6a
CK+SR	47.5±1.9a	37.4±0.3 c	81.9±0.9a	74.7±1.7b
NP+S	42.8±1.0b	42.1±2.0b	71.7±0.1b	69.8±1.8c
NP+SR	44.2±1.9b	41.3±0.2b	68.7±0.8c	74.4±0.7b
施肥 Fertilization (F)	0.429	0.266	P<0.01	P<0.01
根际沉积 Rhizodeposition (R)	P<0.01	P<0.01	P<0.01	P<0.01
F×R	P<0.01	P<0.01	P<0.01	P<0.01