Long-term fertilization effects on soil aggregates organic carbon sequestration and distribution in a yellow-mud paddy soil
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摘要: 本文旨在研究长期不同施肥处理对南方黄泥田团聚体有机碳固持及其组分分配的影响, 为合理培肥及土壤碳库管理提供依据。基于始于1983年的在黄泥田进行的长期定位试验, 选择不施肥(CK)、单施化肥(NPK)、化肥+牛粪(NPKM)与化肥+全量稻秸还田(NPKS) 4个处理, 采集第36年各处理耕层土壤样品并分析各粒级团聚体有机碳固持及其组分变化。结果表明, 黄泥田耕层土壤以大团聚体(>2 mm)和中间团聚体(0.25~2 mm)为主, NPKM与NPKS处理的土壤大团聚体质量比重分别比CK显著增加22.0和15.5个百分点(P<0.05)。与CK相比, NPKM与NPKS处理中大团聚体对有机碳固持贡献率分别提高25.0和19.3个百分点(P<0.05)。施肥处理的大团聚体内轻组有机碳(LF-C)含量较CK显著增加, 其中NPKS处理后大团聚体中LF-C含量较CK增加32.3% (P<0.05)。大团聚体有机碳含量以及该团聚体内的LF-C含量与水稻产量和有机碳投入量都呈极显著正相关(P<0.01)。以上结果表明, 配施牛粪或秸秆还田有利于增加黄泥田大团聚体比例及其有机碳含量, 进而提高有机碳固持贡献率, 尤其是配施牛粪, 而且有机无机肥配施有利于提高大团聚体内轻组有机碳含量与固持贡献, 秸秆还田更为明显, 可为南方黄泥田施肥管理提供依据。Abstract: Agricultural management practices affect carbon sequestration in agricultural soils. This study was performed in southern China to investigate the effects of different fertilizations on soil aggregate organic carbon sequestration and distribution over time in yellow-mud paddy. There were four treatments: no fertilizer (CK), application of chemical fertilizer (NPK), combined application of chemical fertilizer and cattle manure (NPKM), and combined application of chemical fertilizer and straw (NPKS). After 36 years of the experiments (1983 to 2020), the soil samples were collected after rice harvest to analyze soil aggregate, organic carbon sequestration, and distribution. The results showed that macro-aggregates (>2 mm) and medium aggregates (0.25−2 mm) were major components of the bulk soil. Compared to CK, NPKM and NPKS significantly increased the proportions of macro-aggregates by 22.0% and 15.5%, respectively, but greatly decreased the proportions of medium aggregates (0.25−2 mm) by 14.3% and 10.2%, respectively (P<0.05). Application of fertilizer resulted in a significant increase in the organic carbon content of the bulk soil, ranging from 16.9% to 43.9%, compared with the CK treatment. The average organic carbon content of the macro-aggregates was 1.3–1.6 times that of the other aggregates. The organic carbon content of macro-aggregates (>2 mm), medium aggregates (0.25−2 mm), and silt and clay (<0.053 mm) was higher under NPKM than under CK. Furthermore, NPKS increased the organic carbon content of macro-aggregates (>2 mm) compared to CK. The macro-aggregate organic carbon content accounted for 44.5%−63.8% of the total soil organic carbon. Compared with CK, NPKM and NPKS treatments significantly enhanced macro-aggregate organic carbon sequestration by 25.0% and 19.3%, respectively; but decreased the organic carbon sequestration of medium aggregates (0.25−2 mm), micro-aggregates (0.053–0.25 mm), and silt and clay (<0.053 mm). For the macro-aggregates, the light fraction of organic carbon (LF-C) and mineral-associated organic matter (mSOC) were the major parts, and the proportions of mSOC accounted for 50.7%−57.7% of the macro-aggregates. Compared with CK, the content of LF-C increased by 20.7%−32.3% in the fertilization treatments, respectively, and the contribution of LF-C to total soil organic carbon was most significantly increased by 8.9% and 9.4% under the NPKM and NPKS treatments (P<0.05), respectively. For the medium aggregates, the organic carbon content of the fine fraction organic carbon was significantly higher under NPKM treatment than under other treatments (P<0.05); other sub-fractions was not affected by the application of fertilizer. The coarse fraction of organic carbon (CF-C) and mSOC were the major components of the organic carbon in medium aggregates. NPKM and NPKS significantly decreased the sequestration of LF-C, CF-C, and mSOC in medium aggregates compared with the NPK and CK treatments (P<0.05). The organic carbon content of the bulk soil was found to be significantly correlated with rice yield and organic input (P<0.01). Both macro-aggregate organic carbon content and LF-C content showed a significant positive correlation with rice yield (P<0.01). They were also significantly positively correlated with the organic carbon input (P<0.01). Overall, the combined application of chemical fertilizer with cattle mature or straw could increase the proportions and content of organic carbon of macro-aggregates, thus promoting the contribution of total soil organic carbon, especially with the application of cattle manure. Additionally, the combined application of chemical fertilizer and straw was beneficial in promoting macro-aggregate LF-C content and the contribution of total soil organic carbon. The organic carbon content and fractions of active carbon in macro-aggregates are closely related to the productivity of yellow-mud paddy soil. The results provide methods for fertilization management of yellow-mud paddy soil in southern China.
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图 1 不同施肥处理对耕层(0~20 cm)土壤团聚体组成的影响
CK: 不施肥; NPK: 单施化肥; NPKM: 化肥配施牛粪; NPKS: 化肥配施稻秸。不同小写字母表示同一粒径团聚体在不同处理下差异显著(P<0.05)。CK: no fertilizer; NPK: application of chemical fertilizers; NPKM: combined application of chemical fertilizer and cattle manure; NPKS: combined application of chemical fertilizer and straw. Different lowercase letters indicate significant differences for the same size soil aggregates among different treatments at P<0.05.
Figure 1. Effect of different fertilizations on the percentage of soil aggregates of 0−20 cm soil layer
图 2 不同施肥处理对耕层(0~20 cm)土壤团聚体有机碳含量的影响
CK: 不施肥; NPK: 单施化肥; NPKM: 化肥配施牛粪; NPKS: 化肥配施稻秸。不同小写字母表示同一粒径团聚体在不同处理下差异显著(P<0.05)。CK: no fertilizer; NPK: application of chemical fertilizers; NPKM: combined application of chemical fertilizer and cattle manure; NPKS: combined application of chemical fertilizer and straw. Different lowercase letters mean significant differences for the same aggregate size among treatments at P<0.05.
Figure 2. Effect of different fertilizations on the organic carbon content of soil aggregates in 0−20 cm layer
图 3 不同施肥处理对土壤大团聚体(>2 mm)内有机碳组分含量(A)与质量比例(B)的影响
CK: 不施肥; NPK: 单施化肥; NPKM: 化肥配施牛粪; NPKS: 化肥配施稻秸。LF-C: 轻组有机碳; CF-C: 粗颗粒有机碳; FF-C: 细颗粒有机碳; mSOC: 矿物结合态有机碳。不同小写字母表示同一有机碳组分不同处理下差异显著(P<0.05)。CK: no fertilizer; NPK: application of chemical fertilizers; NPKM: combined application of chemical fertilizer and cattle manure; NPKS: combined application of chemical fertilizer and straw. LF-C: light fraction organic carbon; CF-C: coarse fraction organic carbon; FF-C: fine fraction organic carbon; mSOC: mineral-associated organic carbon. Different lowercase letters for the same organic carbon fraction mean significant differences among treatments at P<0.05.
Figure 3. Effect of different fertilizations on contents (A) and mass proportions (B) of different organic carbon fractions in soil macro-aggregates (>2 mm)
图 4 不同施肥处理对土壤中间团聚体有机碳组分含量(A)与质量比例(B)的影响
CK: 不施肥; NPK: 单施化肥; NPKM: 化肥配施牛粪; NPKS: 化肥配施稻秸。LF-C: 轻组有机碳; CF-C: 粗颗粒有机碳; FF-C: 细颗粒有机碳; mSOC: 矿物结合态有机碳。不同小写字母表示同一有机碳组分在不同处理下差异显著(P<0.05)。CK: no fertilizer; NPK: application of chemical fertilizers; NPKM: combined application of chemical fertilizer and cattle manure; NPKS: combined application of chemical fertilizer and straw. LF-C: light fraction organic carbon; CF-C: coarse fraction organic carbon; FF-C: fine fraction organic carbon; mSOC: mineral-associated organic carbon. Different lowercase letters for ghe same organic carbon fraction mean significant differences among treatments at P<0.05.
Figure 4. Effect of different fertilizations on contents (A) and mass proportions (B) of different organic carbon fractions in soil medium-aggregates
图 5 土壤和团聚体有机碳含量与水稻产量和有机碳投入的拟合方程
A、B表示原土有机碳含量与水稻产量和有机碳投入的拟合方程; C、D表示大团聚体(>2 mm)有机碳含量与水稻产量和有机碳投入的拟合方程; E、F表示大团聚体(>2 mm)中轻组有机碳含量与水稻产量和有机碳投入的拟合方程。LF-C为轻组有机碳。*、**和***分别表示在P<0.05、P<0.01和P<0.001水平显著。A, B are fitting curves of bulk soil organic carbon content with grain yield and organic carbon input; C, D are fitting curves of macro-aggregates (>2 mm) organic carbon content with grain yield and organic carbon input; E, F are fitting curves of macro-aggregates light fraction organic carbon content with grain yield and organic carbon input. LF-C is light fraction organic carbon. *, ** and *** indicate significant correlation at P<0.05, P<0.01 and P<0.001, respectively.
Figure 5. Fitting curves between soil organic carbon content with grain yield and organic carbon input
表 1 不同施肥处理有机碳多年平均投入量
Table 1. Multi-year average of organic carbon inputs under different fertilization treatments
t(C)∙hm−2∙a−1 处理
Treatment双季稻年份
Year of double-cropping rice单季稻年份
Year of single-cropping riceCK 1.12 0.91 NPK 2.05 1.38 NPKM 4.18 2.55 NPKS 5.01 3.52 CK: 不施肥; NPK: 单施化肥; NPKM: 化肥配施牛粪; NPKS: 化肥配施稻秸。CK: no fertilizer; NPK: application of chemical fertilizers; NPKM: combined application of chemical fertilizer and cattle manure; NPKS: combined application of chemical fertilizer and straw. 
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表 2 不同施肥处理下各粒径团聚体对全土有机碳固持贡献率
Table 2. Contribution rates of organic carbon soil aggregates to bulk soil organic carbon under different fertilizations
处理
Treatment土壤团聚体粒径 Soil aggregate size (mm) >2 0.25~2 0.053~0.25 <0.053 % CK 44.48±2.15b 39.09±2.20a 10.46±1.36a 5.97±0.07a NPK 47.70±9.17b 39.87±7.11a 7.61±2.54ab 4.83±0.82ab NPKM 69.53±3.97a 22.89±4.12b 3.75±0.01c 3.82±0.25b NPKS 63.84±5.14a 26.51±2.68b 5.32±2.20bc 4.34±0.91b CK: 不施肥; NPK: 单施化肥; NPKM: 化肥配施牛粪; NPKS: 化肥配施稻秸。同列不同小写字母表示不同处理间差异显著(P<0.05)。CK: no fertilizer; NPK: application of chemical fertilizers; NPKM: combined application of chemical fertilizer and cattle manure; NPKS: combined application of chemical fertilizer and straw. Different lowercase letters in the same column mean significant differences among treatments at P<0.05.
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表 3 不同施肥处理下土壤大团聚体(>2 mm)有机碳组分对原土有机碳固持的贡献率
Table 3. Contribution rates of organic carbon fractions in soil macro-aggregates to bulk soil organic carbon under different fertilizations
处理 Treatment LF-C CF-C FF-C mSOC % CK 9.30±0.98c 2.90±0.73b 6.60±2.35b 25.68±1.32b NPK 12.91±1.73b 3.98±1.14ab 5.04±0.48b 25.77±3.11b NPKM 18.23±2.69a 6.62±2.52a 10.15±2.46a 34.53±5.67a NPKS 18.67±1.76a 5.11±1.85ab 7.65±0.12ab 32.41±2.30a CK: 不施肥; NPK: 单施化肥; NPKM: 化肥配施牛粪; NPKS: 化肥配施稻秸。LF-C: 轻组有机碳; CF-C: 粗颗粒有机碳; FF-C: 细颗粒有机碳; mSOC: 矿物结合态有机碳。同列不同小写字母表示不同处理间差异显著(P<0.05)。CK: no fertilizer; NPK: application of chemical fertilizers; NPKM: combined application of chemical fertilizer and cattle manure; NPKS: combined application of chemical fertilizer and straw. LF-C: light fraction organic carbon; CF-C: coarse fraction organic carbon; FF-C: fine fraction organic carbon; mSOC: mineral-associated organic carbon. Different lowercase letters in the same column mean significant differences among treatments at P<0.05.
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表 4 不同施肥处理下中间团聚体内有机碳组分对全土有机碳固持的贡献率
Table 4. Contribution rates of organic carbon fractions in soil medium-aggregates to bulk soil organic carbon under different fertilizations
处理
TreatmentLF-C CF-C FF-C mSOC % CK 7.72±0.25a 2.32±0.21a 3.96±0.92a 25.09±0.54a NPK 8.04±0.99a 2.23±0.61a 3.38±1.09ab 26.22±0.52a NPKM 5.06±0.52c 1.14±0.27b 2.39±0.86ab 14.30±0.96c NPKS 6.32±0.45b 1.43±0.17b 1.87±0.52b 16.89±0.86b CK: 不施肥; NPK: 单施化肥; NPKM: 化肥配施牛粪; NPKS: 化肥配施稻秸。LF-C: 轻组有机碳; CF-C: 粗颗粒有机碳; FF-C: 细颗粒有机碳; mSOC: 矿物结合态有机碳。同列不同小写字母表示不同处理间差异显著(P<0.05)。CK: no fertilizer; NPK: application of chemical fertilizers; NPKM: combined application of chemical fertilizer and cattle manure; NPKS: combined application of chemical fertilizer and straw. LF-C: light fraction organic carbon; CF-C: coarse fraction organic carbon; FF-C: fine fraction organic carbon; mSOC: mineral-associated organic carbon. Different lowercase letters in the same column mean significant differences among treatments at P<0.05.
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表 5 团聚体有机碳组分含量与水稻产量及有机碳投入的相关性
Table 5. Relationship between rice yield, soil organic carbon and organic carbon input
组分
Component籽粒产量
Yield of grain (kg∙hm−2)稻秸产量
Yield of straw (kg∙hm−2)有机碳投入
Organic carbon input (kg∙hm−2)原土有机碳 Bulk soil organic carbon — 0.89** 0.91** 0.78** 团聚体内有机碳
Organic carbon in different soil aggregates>2 mm 0.84** 0.84** 0.77** 0.25~2 mm 0.64* 0.61* 0.28 0.053~0.25 mm 0.31 0.40 0.18 <0.053 mm 0.45 0.53 0.38 大团聚体内有机碳
Organic carbon in macro-aggregateLF-C 0.88** 0.87** 0.78** CF-C 0.63* 0.71** 0.43 FF-C 0.25 0.26 0.50 mSOC 0.58* 0.58* 0.44 中间团聚体内有机碳
Organic carbon in medium-aggregateLF-C −0.06 0.17 −0.01 CF-C −0.56* −0.53 −0.34 FF-C 0.20 0.16 −0.12 mSOC 0.45 0.57* 0.49 LF-C: 轻组有机碳; CF-C: 粗颗粒有机碳; FF-C: 细颗粒有机碳; mSOC: 矿物结合态有机碳。*和**表示P<0.05和P<0.01水平显著相关(n=12)。 LF-C: light fraction organic carbon; CF-C: coarse fraction organic carbon; FF-C: fine fraction organic carbon; mSOC: mineral-associated organic carbon. * and ** indicate significant correlation at P<0.05 and P<0.01, respectively (n=12).
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