不同管理方式对黑土农田根际土壤团聚体稳定性的影响

以长期定位试验为平台,采集草地(GL)、作物轮作(当季作物为大豆,RS)和连作(玉米、大豆、小麦连作,CM,CS,CW)共5个样地的根际土壤样品作为实验处理,通过对根际土壤团聚体稳定性及有机碳含量的研究,旨在阐明不同植被覆盖与作物轮作—连作对土壤团聚体稳定性的影响。结果表明,土壤有机碳以如下顺序递减:GL>CS>CM>RS>CW;土壤全氮含量以如下顺序递减:GL>CS>CM>CW>RS。农田经过20年的生态恢复,植被演替成为草地,土壤有机碳含量比农田各处理平均高出7.8%。水稳性大团聚体(WSA_(>0.25mm))质量分数以如下顺序递减:GL>CM>RS>CS>CW,草地WSA_(>0.25mm)的质量分数比农田平均高出18.0%。WSA_(>0.25mm)有机碳含量与土壤总有机碳含量呈显著正相关(r=0.89,p<0.05)。从草地到农田各处理WSA_(>2mm)与其WSA_(>0.25mm)的变化趋势基本一致。WSA_(>2mm)有机碳含量与平均重量直径(MWD)呈极显著正相关(r=0.99.p<0.01),对土壤团聚体的稳定性具有重要作用。根密度与WSA_(>0.25mm)、WSA_(>2mm)质量分数及有机碳含量呈显著或极显著正相关,与MWD的相关性也达极显著水平(r=0.97,p<0.01),表明植物根系在水稳性大团聚体的形成与稳定过程中起着重要作用。

Aggregate Stability of Rhizosphere Soil as Affected by Land Management in Black Soil

The typical black soil (Mollisol),the most fertile and productive soils distributed in Northeast Chi- na,was subjected to conversion from prairie-grass vegetation to cropland,resulting in deteriorative changes of soil properties after reclamation a century ago.To examine the impact of land management practices on soil organic carbon (SOC) pools and aggregate stability of rhizospere soils,we determined SOC in whole soil and various size aggregates from two long-term experiments (16,20 a).The soil management systems were grassland (GL) and croplands which had four treatments:continuous maize (CM),continuous soybean (CS),continuous wheat (CW),and rotation system (RS).SOC content in rhizosphere soil decreased in the order of GL>CS>CM>RS>CW,while the total soil nitrogen showed an order:GL>CS>CM>CW>RS.SOC content of GL increased by 7.8% as compared to the average of croplands after 20 years of natural vegetation restoration.The percentages of water-stable aggregate (>0.25 mm) (WSA_(>0.25mm)) de- creased in the order:GL>CM>RS>CS>CW in the rhizosphere soil.WSA_(>2mm),the most important fraction for C storage in GL,accounted for 39.0% of the whole soil.A significant positive correlation was found between C stored in WSA_(>0.25mm) and total SOC (r=0.89,p<0.05),and between the mean weight diameters (MWD) of aggregates and C stored in WSA_(>2mm)(r=0.99,p<0.01).Root density was found to significantly correlate with WSA_(>0.25mm),WSA_(>2mm) and MWD at p<0.05 or p<0.01,respectively.In con- clusion,root system played a vital role in formation and stability of soil macroaggregates.