长期不同施氮量下黑土团聚体稳定性及有机碳含量的变化

为测定不同氮肥施用量对黑土团聚体组成及稳定性、有机碳含量及团聚体有机碳分布的影响,阐明黑土有机碳稳定性对不同施氮水平的响应机制,本研究在吉林省梨树县不同施氮水平长期定位试验田进行取样,以施氮水平不同设置5个处理,分别为T1(0)、T2(160 kg·hm^-2)、T3(240 kg·hm^-2)、T4(280 kg·hm^-2)、T5(320 kg·hm^-2),分析长期不同施氮量下水稳性团聚体组成、团聚体结构特征、土壤总有机碳含量及团聚体有机碳分布的变化,探究酸化黑土有机碳含量影响特征。结果表明：随氮肥施用水平的升高,土壤碱解氮(AN)和全氮(TN)含量先增后减,T3处理含量最高,AN和TN分别比T1处理高24.90%、10.28%;土壤速效磷(AP)的含量呈下降趋势。随氮肥用量的提高,土壤团聚体呈现大粒径团聚体向小粒径团聚体转变的趋势,>2 mm粒径团聚体下降14.55%。土壤有机碳总量随施氮水平的提高呈先增后减的趋势,施氮量为280 kg·hm^-2有机碳含量最高;>2...

Changes in aggregates stability and organic carbon content of black soil following the use of different longterm 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.