秸秆还田与施氮对耕层土壤有机碳储量、组分和团聚体的影响

doi:10.3864/j.issn.0578-1752.2023.20.009

摘要/Abstract

摘要：

【目的】秸秆还田配施氮肥的固碳研究结果存在争议，为此展开本研究，旨在揭示秸秆还田配施氮肥对农田土壤固碳能力的影响以及固碳机理，为秸秆还田配施氮肥固碳研究提供依据。【方法】依托11年的长期定位试验，采用裂区设计，主处理为秸秆处理方式（还田与不还田），副处理为3个施氮水平，分别为不施氮（N0）、施氮 168 kg·hm^-2（N168）、336 kg·hm^-2（N336，过量施氮）。【结果】施用氮肥较不施氮肥小麦增产14.4%—19.5%，秸秆还田对产量影响不显著。秸秆还田显著提高土壤碳累积投入量70.8%（P<0.05），但对土壤有机碳储量影响不显著。与不施氮相比，施用氮肥分别显著提高土壤碳累积投入量和土壤有机碳储量7.7%—8.5%（P<0.05）和4.7%—8.1%（P<0.05）。施用氮肥显著提高土壤固碳速率32.7%—56.1%（P<0.05），过量施氮（N336）显著提高土壤固碳效率51.8%（P<0.05）;秸秆还田显著降低了土壤固碳效率30.9%（P<0.05）。施氮和秸秆还田均能提升土壤碳库容量，N0和N168处理已经达到碳饱和状态。秸秆还田后土壤可溶性有机碳（DOC）、微生物量碳（MBC）、易氧化有机碳（EO）含量分别提高4.6%、11.2%、4.5%。与不施氮（N0）相比，施氮（N168）和过量施氮（N336）的DOC分别提高14.1%、29.5%;MBC分别平均降低14.0%、28.0%;EO分别提高8.2%和11.5%。秸秆还田有利于土壤DOC/SOC、微生物熵的提高。施用氮肥有利于DOC/SOC的提升，但降低了微生物熵。秸秆还田与施用氮肥均对土壤EO/SOC没有影响。秸秆还田和施氮均有利于大团聚体（>0.25 mm）的提升，秸秆还田显著提升了大团聚体的有机碳含量5.2%。秸秆不还田下团聚体平均重量直径（MWD）和几何平均直径（GMD）随着氮水平增加表现出先提高后降低的趋势，还田下则表现为随氮水平的增加而增加，秸秆还田分别提升团聚体MWD和GMD 8.8%和7.5%，施用氮肥相较不施氮对MWD和GMD分别提升14.1%—22.7%和16.8%—23.4%。秸秆还田和施氮均能提高有机碳在大团聚体的分布。【结论】秸秆还田配施氮肥可以通过增加碳投入量，提高活性有机碳含量，降低微生物活性，提高团聚体对有机碳的保护来提高耕层碳储量。

关键词: 秸秆还田, 氮肥, 耕层, 碳储量, 活性碳组分, 团聚体

Abstract:

【Objective】The results of carbon sequestration studies on combining straw returning with nitrogen fertilizer are controversial. Aimed at such problem, this experiment was carried out to reveal the effects of combining straw returning with nitrogen fertilizer on Carbon sequestration capacity and mechanism of farmland, so as to provide a reference for the future research. 【Method】Based on 11 years of long-term positioning experiments, this paper adopted split-zone design, the main treatment included straw returning to soil and removal straw from field, and the subplots included three N application rate, which were no nitrogen (N0), 168 kg·hm^-2 (N168, nitrogen), and 336 kg·hm^-2 (N336, excessive nitrogen application). 【Result】Compared with wheat without nitrogen fertilizer, wheat yield increased by 14.4%-19.5% with nitrogen fertilizer. The effect of straw returning to the field on yield was not significant. Straw returning significantly increased the cumulative input of soil carbon by 70.8% (P<0.05), but had no significant effect on soil organic carbon storage. Compared N0, the nitrogen application significantly increased soil carbon accumulation input and soil organic carbon storage by 7.7%-8.5% (P<0.05) and 4.7%-8.1% (P<0.05), respectively. The application of nitrogen fertilizer significantly increased the carbon fixation rate by 32.7%-56.1% (P<0.05), and N336 significantly increased the soil carbon fixation efficiency by 51.8% (P<0.05); straw returning to the field did not significantly improve the soil carbon fixation rate, but significantly reduced the carbon fixation efficiency by 30.9% (P<0.05). Both nitrogen application and straw returning could improve soil carbon pool capacity, and N0 and N168 have reached carbon saturation. The content of soluble organic carbon (DOC), microbial biomass carbon (MBC) and easily oxidized organic carbon (EO) in the soil increased by 4.6%, 11.2% and 4.5% respectively after returning straw to the field. Compared N0, DOC under N168 and N336 increased by 14.12% and 29.54% respectively; MBC decreased by 14.0% and 28.0% on average, respectively; EO increased by 8.2% and 11.5%, respectively. Straw returning to the field was beneficial to the improvement of soil DOC/SOC and microbial entropy. Applying nitrogen fertilizer was beneficial to the increase of DOC/SOC, but reduced the microbial entropy. Both straw returning and nitrogen fertilizer application had no effect on soil EO/SOC. Both straw returning and nitrogen application were beneficial to the improvement of macroaggregates (>0.25 mm), and straw returning significantly increased the organic carbon content of macroaggregates by 5.2%. The average weight diameter (MWD) and geometric average diameter (GMD) of aggregates under non-return showed a trend of first increasing and then decreasing with the increase of nitrogen level, while under straw returning, it showed an increase with the increase of nitrogen level. Straw returning increased the MWD and GMD of aggregates by 8.8% and 7.5% respectively, and the application of nitrogen fertilizer increased the MWD and GMD by 14.1%-22.7% and 16.8%-23.4% respectively, compared with CK. Both straw returning and nitrogen application could improve the distribution of organic carbon in large aggregates. 【Conclusion】Straw returning with nitrogen fertilizer could increase carbon input, increase activated organic carbon content, reduce microbial activity, and improve the protection of organic carbon by aggregates.

Key words: straw returning, nitrogen fertilizer, tillage layer, carbon storage, activated carbon components, aggregates

郭戎博, 李国栋, 潘梦雨, 郑险峰, 王朝辉, 何刚. 秸秆还田与施氮对耕层土壤有机碳储量、组分和团聚体的影响[J]. 中国农业科学, 2023, 56(20): 4035-4048.

GUO RongBo, LI GuoDong, PAN MengYu, ZHENG XianFeng, WANG ZhaoHui, HE Gang. Effects of Long-Term Straw Return and Nitrogen Application Rate on Organic Carbon Storage, Components and Aggregates in Cultivated Layers[J]. Scientia Agricultura Sinica, 2023, 56(20): 4035-4048.

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项目 Item	小麦产量 Wheat yield	碳投入量 CI	碳储量 SOC_S	固碳速率 SOC_SR	固碳效率SOC_SE	微生物量碳 MBC	可溶性有机碳 DOC	易氧化碳 EO	平均重量直径 MWD	几何平均直径 GMD
秸秆还田 Straw returning (S)	0.002^NS	14511^**	5.5^NS	5.5^NS	22.3^**	8.5^**	0.6^NS	1.8^NS	2.2^NS	1.9^NS
氮肥用量 N rate (N)	47.2^**	36.3^**	6.4^*	6.4^*	4.4^**	45.6^**	6.5^**	4.3^*	13.1^**	14^**
N╳S	1.4^NS	1.1^NS	0.5^NS	0.5^NS	1.3^NS	1.1^NS	0.12^NS	0.5^NS	6.6^**	3.2^NS

处理 Treatment	有机碳储量 SOCs (t·hm^-2)	固碳量 ∆SOCs( t·hm^-2)	固碳速率 SOC_SR (kg·hm^-2·a^-1)	固碳效率 SOC_SE (%)
N0	30.0 b	3.6 b	331.0 b	8.2 bc
N168	31.9 ab	5.5 ab	501.4 ab	11.6 ab
N336	33.2 a	6.8 a	620.1 a	14.3 a
S+N0	31.7 ab	5.3 ab	480.7 ab	7.0 c
S+N168	32.7 a	6.3 a	575.6 a	7.8 bc
S+N336	33.5 a	7.1 a	646.8 a	8.8 bc

处理 Treatment	可溶性有机碳/总有机碳 DOC/SOC (%)	微生物熵 MBC/SOC (%)	易氧化有机碳/总有机碳 EO/SOC (%)
N0	1.6 b	1.2 a	25.6 a
N168	1.7 ab	1.0 ab	27.1 a
N336	1.8 ab	0.8 b	26.4 a
S+N0	1.5 b	1.3 a	26.5 a
S+N168	1.7 ab	1.0 ab	26.7 a
S+N336	1.9 a	0.9 ab	27.0 a

项目 Item	处理 Treatment	团聚体大小 Aggregate size (mm)
项目 Item	处理 Treatment	>2	2-1	1-0.5	0.5-0.25	<0.25
团聚体组成 Aggregate composition (%)	N0	7.7 b	10.0 c	21.8 c	18.7 a	41.9 a
	N168	9.4 ab	12.3 b	30.0 ab	18.0 ab	33.3 c
	N336	8.2 b	12.0 bc	26.3 ab	19.8 a	33.8 bc
	S+N0	7.8 b	11.0 bc	23.9 bc	18.5 a	38.9 ab
	S+N168	8.1 b	12.9 b	27.2 a	18.5 a	33.3 c
	S+N336	11.8 a	15.7 a	28.7 a	15.7 b	29.7 c
团聚体有机碳含量 SOC of aggregates (g·kg^-1)	N0	13.7 ab	13.5 b	12.9 ab	11.0 ab	11.1 ab
	N168	12.8 b	13.7 ab	12.4 ab	10.6 b	11.0 b
	N336	14.61 a	14.0 ab	12.1 b	10.5 b	10.7 b
	S+N0	14.1 ab	14.1 ab	12.9 ab	10.8 ab	10.7 b
	S+N168	14.4 a	14.0 ab	13.2 a	11.4 a	11.6 ab
	S+N336	15.2 a	14.7 a	13.0 a	11.1 ab	12.1 a
团聚体有机碳分布 Distribution percentage of SOC in aggregates (%)	N0	9.1 b	11.2 c	23.4 c	17.1 a	39.1 a
	N168	10.2 ab	14.3 b	28.3 ab	16.1 a	31.1 bc
	N336	10.1b	14.2 b	27.3 ab	17.7 a	30.7 bc
	S+N0	9.2 b	12.9 bc	26.0 b	16.7 a	35.1 ab
	S+N168	9.4 b	14.3 b	28.6 a	16.8 a	30.8 bc
	S+N336	13.5 a	17.5 a	28.3 a	13.3 b	27.3 c