摘要:华北平原是我国主要的粮食生产基地之一, 小麦-玉米轮作是本区域主要种植模式。长期秸秆全量还田与土壤的浅旋耕造成了土壤耕层变浅、犁底层加厚、养分表聚等一系列土壤质量问题, 已成为制约本区域粮食持续高产、稳产的障碍因素。本研究依托中国科学院栾城农业生态系统试验站转变耕作与秸秆还田方式定位试验, 开展不同耕作措施和秸秆还田方式对土壤团聚体组成及其稳定性、有机碳氮在团聚体中分布影响的研究, 为阐释不同农业管理措施下土壤碳氮的物理保护机制提供依据。试验设5个处理: 无秸秆旋耕(对照1)、秸秆旋耕还田(对照2)、秸秆深翻耕还田、秸秆集中深混埋、秸秆集中深埋, 后3个处理作为转变秸秆还田方式处理。研究结果表明, 改变秸秆旋耕还田为深层还田可以显著提高粒径>0.25 mm团聚体含量; 不同秸秆还田方式对>2 mm的大团聚体和0.25~2 mm的小团聚体的水稳性影响存在较大差异, 秸秆深层还田主要增加10 cm以下土层土壤水稳性大团聚体(>2 mm)含量和表层水稳性小团聚体(0.25~2 mm)含量, 大团聚体和小团聚体的水稳性消长受到了秸秆还田方式的影响。秸秆深层还田显著增加了亚耕层(20~40 cm)土壤团聚体稳定率, 降低了其结构破碎率。秸秆深层还田措施使0~40 cm土层土壤有效融合, 消除了耕层土壤养分表聚现象, 显著增加了亚耕层土壤有机碳氮含量以及大团聚体对土壤有机碳氮的贡献率, >2 mm团聚体有机碳和氮贡献率在20~40 cm土层分别平均为42.2%~44.0%和32.8%~49.9%, 分别比秸秆旋耕还田处理增加48.7%~54.9%和32.8%~101.8%。总之, 秸秆深层还田有利于改善耕层土壤结构, 促进土壤有效融合, 消除土壤表聚现象。
关键词:耕作/
秸秆还田/
有机碳/
氮素/
土壤团聚体
Abstract:The North China Plain is a major grain production area in China, and wheat-maize rotation is the main cropping pattern in this region. Long-term straw returning and shallow rotary tillage have caused soil quality problems, such as a shallow plow soil layer, thickening of the plow bottom, and nutrient accumulation at the soil surface. These problems restrict a sustainable and stable grain yield. This study examined the effects of different agricultural management practices of tillage measures and methods of straw returning of physical protection on the soil aggregate composition and stability, the distribution of organic carbon and nitrogen in the aggregates at the Luancheng Agricultural Ecosystem Experimental Station, Chinese Academy of Sciences. A tillage and straw counters-field positioning experiment was conducted from 2016 with five treatments: no-straw and rotary tillage (as control 1, RT), straw mulching and rotary tillage (as control 2, SR), straw mulching and deep ploughing (SP), straw incorporated into 0?40 cm soil layer of 40 wild no-wheat planting belt (SID), and straw buried into 30?40 cm soil layer (SBD). The three latter treatments represented different straw returning methods. The results showed that changing rotary tillage to deep tillage under straw returning significantly increased the content of large macroaggregates (>0.25 mm). Different straw returning methods led to significantly different changes in water stability of the large (>2 mm) and small (0.25–2 mm) macroaggregates. Straw returning to the deep soil layer increased the content of large water-stable macroaggregates in soil layers below 10 cm (>2 mm), whereas increased the content of small water-stable macroaggregates (0.25–2 mm) in the surface layer. The changes in the water stability of large and small macroaggregates were impacted by the straw returning method. Straw returning to deep soil layer significantly increased the stability in the subsurface layer (20–40 cm) and decreased the structural fragmentation rate of soil aggregates. Deep straw returning effectively integrated the 0–40 cm soil layer, eliminated the surface accumulation of nutrients, and significantly increased the soil organic carbon and nitrogen contents in the subsurface layer and the contribution of large macroaggregates to soil organic carbon and nitrogen. The contribution of organic carbon and nitrogen of the macroaggregates (>2 mm) in the 20–40 cm soil layer was 42.2%–44.0% and 32.8%–49.9%, respectively, which increased by 48.7%–54.9% and 32.8%–101.8%, respectively, compared to straw-free rotary tillage. In summary, the straw returning to deep soil layer improved soil structure of tillage layer, promoted integration of soil layers and emilimated nutrient accumulation in soil surface layer.
Key words:Tillage/
Straw returning/
Organic carbon/
Nitrogen/
Soil aggregate
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