北方典型水稻土有机质及其组分演变特征

【目的】探究我国北方淹育型水稻土在开垦耕种过程中土壤有机质及其组分的演变特征，为提高水稻土有机质的品质、合理利用水稻土及提高其生产潜力、建设高产稳产稻田提供理论依据和数据支撑。【方法】本研究以辽宁省各地棕壤和草甸土上发育的不同开垦年限淹育型水稻土为研究对象，通过野外调查、田间定点试验及室内测试分析等手段，研究了开垦年限对水稻土有机质含量与组成及其腐殖质特性的影响。【结果】水稻土耕层有机质总量 (SOM) 随开垦年限的增加维持在18.60～26.30 g/kg之间，与开垦年限无显著相关关系 (P > 0.05)，但易氧化有机质含量占有机质总量的比例 (ROM/SOM) 均在50%以上，并且随水稻土开垦年限增加而下降，降幅为18%～20%；有机质氧化稳定系数 (Kos) 均在1.2以下，随着水稻土开垦年限增加呈上升趋势，增幅为52%～57%，胡富比 (HA/FA) 及胡敏酸相对色度 (RF) 随开垦年限增加而增大，但胡敏酸活化度 (AD) 和土壤腐殖质的松/紧 (LCH/TCH) 明显下降。【结论】北方水稻土随着开垦年限的增加，土壤中的有机质稳定性增加，活性降低，耕层土壤对养分的供、贮能力减弱，土壤肥力水平下降，限制了北方水稻土生产潜力的发挥，应通过耕作管理和有机无机肥料配施来防止或减缓水稻土肥力的下降。

Evolutionary characteristics of organic matter and its components in typical paddy soils in northern China

【Objectives】The objective of this research is to explore the evolutionary characteristics of soil organic matter (SOM) and its components during the cultivation history of paddy soil in northern China, and to provide theoretical basis and data support for the improvement of SOM quality, rational utilization of paddy soil and improving its production potential, and establishment of high and stable-yielding paddy fields.【Methods】The submerged paddy soils developed from brown soils and meadow soils in different planting years in Liaoning Province were chosen as the research objects. Combining investigation, field fixed-site test and indoor analysis, the effects of rice cultivation history on the content and fractions of SOM and humus characteristics of paddy soil were elucidated.【Results】There was no significant correlation between the total SOM content and the age of rice cultivation (P > 0.05), and the total SOM content was maintained at 18.60–26.3 g/kg. With the increment of rice cultivation years, the proportion of easily oxidized organic matter (ROM) in SOM was reduced by 18%–20%, even though its content was above 50% at the beginning, and the organic matter oxidation stability coefficient (Kos) was below 1.2, with an increase of 52%–57%. The ratio of humic acid to fulvic acid (HA/FA) and the relative color (RF) of HA were increased, the activation degree of humic acids (AD) and the looseness/tightness of soil humus decreased significantly, with the increment of the rice cultivation years, respectively.【Conclusions】With the extension of the planting years of rice, the soil organic matter become stable in property and less active, which leads to weakened ability of paddy soil in supplying and storing nutrients, and is unfavorable for exerting the production potential of the paddy fields. Appropriate tillage and nutrient managements should be considered to slow down and prevent the decline of soil fertility eventually.