Northeast Key Laboratory of Conservation and Improvement of Cultivated Land (Shenyang), Ministry of Agriculture, College of Land and Environment, Shenyang Agricultural University, Shenyang, 110866, Liaoning, China.
Institute of Bio- and Geosciences, Agrosphere (IBG-3), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße, 52428, Jülich, Germany.
Sci Rep. 2021 Sep 9;11(1):17899. doi: 10.1038/s41598-021-97546-3.
Straw incorporation is an effective measure for increasing soil organic carbon (SOC) thereby improving soil quality and crop productivity. However, quantitative assessments of the transformation and distribution of exogenous carbon (C) in soil aggregates under various field fertilization practices have been lacking. In this study, we collected topsoil samples (0-20 cm) from three fertilization treatments (no fertilization control, CK; inorganic fertilizer, IF; inorganic fertilizer plus manure, IFM) at a 29-year long-term Mollisol experiment in Northeast China. We then mixed the soil samples with C-labeled maize straw (δC = 246.9‰), referred as CKS, IFS, and IFMS, and incubated them in-situ for 360 days. Initial and incubated soil samples were separated into four aggregate fractions (> 2, 1-2, 0.25-1, and < 0.25 mm) using the dry-sieving method, which counted 18%, 17%, 45%, and 21% (averages from the three initial soil samples), respectively. Organic C content was highest in 0.25-1 mm aggregate (6.9-9.6 g kg) prior to incubation, followed by > 2 mm aggregates (2.2-5.8 g kg), 1-2 mm aggregates (2.4-4.6 g kg), and < 0.25 mm aggregates (3.3-4.5 g kg). After 360-day incubation with straw incorporation, organic C content was 2.3-4.5 g kg, 2.9-5.0 g kg, 7.2-11 g kg and 1.8-3.0 g kg in > 2, 1-2, 0.25-1, and < 0.25 mm aggregates, respectively, with the highest in the IFMS treatment. Straw-derived C content was 0.02-0.05 g kg, 0.03-0.04 g kg, 0.11-0.13 g kg, and 0.05-0.10 g kg in > 2, 1-2, 0.25-1, and < 0.25 mm aggregates, respectively. The relative distribution of straw-derived C was highest (40-49%) in 0.25-1 mm aggregate, followed by < 0.25 mm aggregates (21-31%), 1-2 mm aggregates (13-15%), and > 2 mm aggregates (9.4-16%). During the incubation, the relative distribution of straw-derived C exhibited a decrease in > 2 mm and 1-2 mm aggregates, but an increase in the < 0.25 mm aggregate. At the end of incubation, the relative distribution of straw-derived C showed a decrease in the 0.25-1 mm aggregate but an increase in the < 0.25 mm aggregate under the IFMS treatment. This study indicates that more straw-derived C would be accumulated in smaller aggregates over longer period in Mollisols, and combined inorganic and organic fertilization is an effective measure for C sequestration in Northeast China.
秸秆还田是增加土壤有机碳（SOC）从而改善土壤质量和作物生产力的有效措施。然而，对于不同田间施肥措施下外源碳（C）在土壤团聚体中的转化和分布，仍缺乏定量评估。本研究在中国东北一个长达 29 年的黑土长期定位试验中，从无肥对照（CK）、无机肥（IF）和无机肥加粪肥（IFM）三种施肥处理中采集了表层土壤样品（0-20 cm）。然后，我们将土壤样品与 C 标记的玉米秸秆（δC = 246.9‰）混合，分别标记为 CKS、IFS 和 IFMS，并在原位培养 360 天。初始和培养后的土壤样品采用干筛法分离成四个团聚体级分（>2、1-2、0.25-1 和<0.25 mm），分别占 18%、17%、45%和 21%（三个初始土壤样品的平均值）。培养前，0.25-1mm 团聚体中的有机碳含量最高（6.9-9.6 g kg），其次是>2mm 团聚体（2.2-5.8 g kg）、1-2mm 团聚体（2.4-4.6 g kg）和<0.25mm 团聚体（3.3-4.5 g kg）。在 360 天的秸秆培养后，有机碳含量在>2、1-2、0.25-1 和<0.25mm 团聚体中分别为 2.3-4.5、2.9-5.0、7.2-11 和 1.8-3.0 g kg，IFMS 处理中的含量最高。秸秆衍生 C 含量在>2、1-2、0.25-1 和<0.25mm 团聚体中分别为 0.02-0.05、0.03-0.04、0.11-0.13 和 0.05-0.10 g kg。秸秆衍生 C 的相对分布在 0.25-1mm 团聚体中最高（40-49%），其次是<0.25mm 团聚体（21-31%）、1-2mm 团聚体（13-15%）和>2mm 团聚体（9.4-16%）。在培养过程中，秸秆衍生 C 的相对分布在>2mm 和 1-2mm 团聚体中减少，但在<0.25mm 团聚体中增加。在培养结束时，IFMS 处理下 0.25-1mm 团聚体中秸秆衍生 C 的相对分布减少，而<0.25mm 团聚体中增加。本研究表明，在黑土中，外源 C 会在较长时间内更多地积累在较小的团聚体中，无机和有机施肥的结合是中国东北土壤固碳的有效措施。
