摘要
以东北黑土区开垦2 a和开垦30 a的典型旱作土壤为研究对象,采用15N同位素成对标记技术开展室内培养试验,利用数值计算模型(FLUAZ)计算不同开垦年限土壤的氮初级转化速率,以比较不同开垦年限黑土氮初级转化速率和净转化速率的差异,明确开垦年限对黑土氮转化过程的影响。结果表明,与开垦2 a土壤相比,开垦30 a土壤的有机碳和水溶性有机碳含量显著降低,导致土壤氮初级矿化速率和初级固定速率也显著降低。但开垦30 a土壤的初级硝化速率、净硝化速率和净氮矿化速率却显著高于开垦2 a土壤。两个开垦年限土壤的初级硝化速率分别为净硝化速率的1.15倍和1.02倍,说明土壤微生物对硝态氮的固定很少。开垦30 a土壤的m/i值(氮初级矿化速率与初级固定速率之比)和n/ia值(初级硝化速率与初级铵态氮固定速率之比)均显著大于1,而开垦2 a土壤的m/i值和n/ia值均接近1。表明开垦2 a土壤的氮矿化与固定过程紧密偶联,氮素损失的风险较小,而开垦30 a土壤中氮矿化量超过了固定量,这为硝化作用的进行提供了底物,增加了硝酸盐反硝化和淋溶风险。
【Objective】This paper was oriented to explore effect of cultivation,relative to duration,on gross and net N transformation rates in black soil in Northeast China.【Method】Two tracts of upland farmlands of typical black soils,different in cultivation history,2 and 30 years,were selected in Northeast China for the study.Soil samples were collected for in-lab incubation using the 15N pair-labeled technique.Gross N transformation rates in the soils were calculated using the numerical algorithm model(FLUAZ),and net mineralization rates and net nitrification rates were by duration of the incubation and variation of the samples in inorganic nitrogen content or nitrate nitrogen content with the incubation.【Result】The soil of the farmland,30 years in cultivation,was 20.8%and 16.0%lower,respectively,than the one 2 years in cultivation in organic C and water soluble organic C content,and only 62.6%and 42.1%of the latter,respectively,in gross mineralization and immobilization rate.However,the former was significantly higher than or 1.77,2.00,and 7.29 times as high as the latter,respectively,in gross nitrification rate,net nitrification rate,and net mineralization rate.The gross nitrification rate was 1.15 and 1.02 times as high as the net nitrification rate,respectively,in the latter and former,and the immobilized ammonium nitrogen accounted for 60%~97%of the total inorganic nitrogen during the whole incubation period,indicating that little nitrate nitrogen was immobilized by soil microorganisms in these two soils.The values of m/i(the ratio of gross N mineralization rate to immobilization rate)and n/ia(the ratio of gross nitrification rate to ammonium immobilization rate)of the former were both significantly higher than 1,while those of the latter were approximate to 1.【Conclusion】The processes of mineralization and immobilization of nitrogen in the soil,2 years in cultivation,were coupled tightly,posing little risk of nitrogen loss to environment,whereas the amount of mineralized nitrogen was much higher than that of immobilized nitrogen in the soil 30 years in cultivation,thus providing substrate for nitrification and increasing denitrification and leaching risk of nitrate.
作者
李平
郎漫
LI Ping;LANG Man(Jiangsu Key Laboratory of Agricultural Meteorology,Nanjing University of Information Science&Technology,College of Applied Meteorology,Nanjing University of Information Science&Technology,Nanjing 210044,China)
出处
《土壤学报》
CAS
CSCD
北大核心
2020年第1期165-173,共9页
Acta Pedologica Sinica
基金
国家自然科学基金项目（41301345,41101284）资助~~
关键词
开垦年限
黑土
15N标记
氮转化
Duration of cultivation
Black soil
15N trace
Nitrogen transformation
