长期施肥对褐土有机碳和氮素在团聚体中分布的影响

 采集安排在半湿润农田生态系统土垫旱耕人为土（中等肥力红油土）上长达25年的肥料定位试验小区耕层的土样（0～20 cm土层），采用干筛法将供试土样分为5～2、2～1、1～0.25 mm等3个等级团聚体，研究长期施肥对有机碳、全氮、硝态氮和铵态氮在不同粒级土壤团聚体中分布的影响。研究表明：①长期施肥对耕层土壤5～2 mm团聚体含量影响最大。长期施肥，特别是化肥与有机肥配合施用有利于该粒径团聚体的形成。②长期施肥处理能使土壤有机质、全氮以及硝态氮含量有较大幅度增加，但对铵态氮的影响较小。③与不施肥对照相比，经过长期施肥耕层土壤中有机质、全氮在不同粒级的团聚体中的含量差异较大，并且呈现出较强的规律性，均表现为1～0.25 mm粒径团聚体中的含量最高。④长期施肥处理对硝态氮在各级团聚体中的分布影响较大，除化肥＋中量秸秆处理外，其余处理土壤团聚体中硝态氮含量均随团聚体粒径增大而降低。⑤5～2 mm团聚体含量与土壤有机碳、全氮以及硝态氮之间呈显著正相关关系；而1～0.25mm团聚体与土壤全氮含量以及硝态氮含量呈显著负相关关系。说明5～2 mm团聚体是土壤有机质、全氮和硝态氮的主要载体。⑥在绝大部分情况下1～0.25 mm的团聚体对土壤有机碳、全氮、硝态氮的贡献率最大。

Effects of Long-Term Fertilization on Distribution of Organic Matters and Nitrogen in Cinnamon Soil Aggregates

Soil samples,collected from the 25-year long-term fertilizer experiment carried out on the manual loessial soil situated sub-humid farmland ecological system,were used to study the distribution of soil organic matters,total nitrogen,nitrate nitrogen,and ammonium nitrogen in different grades of soil aggregates in order to study the effects of long-term application of organic manures in combination with chemical fertilizers.Result showed that the percentage of mass of the soil macro-aggregates with long-term application of fertilizers,whose sizes are between 5-2 mm,is increased compared with that of the samples with no fertilizer.It is easier to form lager size soil macro-aggregates because of the long-term application of organic manures in combination with chemical fertilizers.As the results show that the contents of organic matters,total nitrogen and nitrate nitrogen are all higher after those treatments with different combinations of fertilizers,while there is a little effect on the contents of ammonium nitrogen after the same treatments.The contents of organic matters,total nitrogen in the grades of soil macro-aggregates from the plough layers of those treated farmland exhibit significant difference.Moreover,the contents of organic matters and total nitrogen in the soil macro-aggregates with the size of 1-0.25 mm is the highest in all types of treated soil samples.The contents of nitrate nitrogen in soil macro-aggregates increase with the increasing of soil macro-aggregate size except those of soil samples with the application ofchemical fertilizer and lower amount of straw.The results of correlation analysis reveal that there exists a significant positive correlation between the percentage of mass of soil macro-aggregates with the size of 5-2 mm and the contents of organic matters and total nitrogen and the nitrate nitrogen in the soil samples.However,the correlation between the percentage of mass of soil macro-aggregates with the size of 1-0.25 mm and the contents of total nitrogen and nitrate nitrogen is significantly negative.From the study it is also showed that the highest contributing rates of macro-aggregates fractions in soil fertility is from the soil macro-aggregates fraction with the size of 1-0.25 mm in most of the cases.