Changes in aggregates stability and organic carbon content of black soil following the use of different long-term nitrogen application rates
This study aimed to determine the effects of different nitrogen fertilizer application rates on aggregate composition and stability,and organic carbon content and distribution within black soil aggregates,and to elucidate the response mechanisms of black soil organic carbon stability to these different nitrogen application levels.Samples were collected from long-term pilot plots with different nitrogen application levels in Lishu County,Jilin Province.Five treatment groups with different nitrogen application levels,T1(0),T2(160 kg·hm-2),T3(240 kg·hm-2),T4(280 kg·hm-2),and T5(320 kg·hm-2),were assessed to analyze the corresponding influence of nitrogen application levels on the organic carbon content of acidified black soil.With an increase in nitrogen fertilizer application level,the content of soil alkaline hydrolyzable nitrogen(AN)and total nitrogen(TN)first increased and then decreased,with the highest contents being observed in the T3 treatment group;AN and TN were 24.90%and 10.28%higher in the T3 group than those in the T1 group,respectively.Nonetheless,the content of soil available phosphorus(AP)showed a decreasing trend with increasing nitrogen application levels.With an increase in nitrogen fertilizer dosage,soil aggregates exhibited an overall transition from large to small particle size aggregates,with a corresponding 14.55%decrease in aggregates with a particle size>2 mm.The total amount of soil organic carbon exhibited an initial increasing trend followed by a decreasing trend with an increasing nitrogen application level;the highest organic carbon content was observed at a nitrogen application rate of 280 kg·hm-2.The organic carbon content in aggregates with particle sizes>2 mm and those ranging from 2 mm to 0.25 mm was relatively high.Further,the correlation between organic carbon content and the aggregate stability characteristics average geometric diameter(GMD),aggregate failure rate(PAD),unstable aggregate index(ELT),and soil chemistry properties was high across the different nitrogen application levels.Throughout 13 years of continuous application of different levels of nitrogen fertilizer,with the continuous increase in nitrogen fertilizer application,the soil organic carbon content exhibited a trend of initially increasing before decreasing.Overall,an increase in nitrogen fertilizer application significantly reduces soil pH;additionally,soil aggregate organic carbon is primarily distributed within particle sizes ranging from 2-0.25 mm in size.
nitrogen application rateblack soilsoil physical and chemical propertyaggregate organic carbonsoil aggregate stability
万方数据
维普
