外源氮素形态对植烟土壤酸解有机态氮组分的影响

Effects of different external nitrogen forms on acidolysis organic nitrogen fractions in tobacco-planting soil

【目的】为明确外源氮形态对植烟土壤酸解有机态氮(AON)组分的影响,为植烟土壤保育与定向培肥提供理论依据。【方法】利用^(15)N示踪技术,以湖北恩施植烟土壤为研究对象,采取土壤培养试验,分析外源添加氨态氮、硝态氮和氨基酸态氮对植烟土壤AON及其组分酸解铵态氮(AN)、氨基酸态氮(ANN)、氨基糖态氮(ASN)和酸解未知态氮(UAN)中的氮素转化的影响。【结果】(1)在0~10 d,氨态氮^(15)N的AON转化率(R值)最高,为50%~70%,氨基酸态氮^(15)N的略低,为45%~55%,硝态氮^(15)N的仅为27%~31%,但随后,各处理R值差别不大,约为30%;(2)氨态氮、硝态氮和氨基酸态氮的AON-^(15)N转入量差别不大,加权均值分别为9.84 mg/kg、8.40 mg/kg和10.49 mg/kg,但不同处理的AON-^(14)N变化值差别较大,氨态氮的加权均值为-116.71 mg/kg,而硝态氮和氨基酸态氮的却为28.05 mg/kg和69.84 mg/kg;(3)基于结构方程模型的路径分析发现,氨态氮的AN-ASN和ASN-UAN路径被增强,r值均为正值,ASN加速了AN向UAN的转化,但氨基酸态氮中被增强的AN-AAN和ANN-UAN的r值均为负值,AAN抑制了AN向UAN的转化;(4)在1 d时,氨态氮的AON含量略高于其它处理,但随后迅速下降,30 d时显著低于硝态氮和氨基酸态氮处理。【结论】不同外源氮形态的AON-^(15)N转入量无明显差别,但对土壤本身^(14)N的转化过程影响较大。氨基酸态氮和硝态氮可通过增加其它来源^(14)N转入量提高了AON,而氨态氮则更有利于土壤本身AON-^(14)N的转出,不利于AON的累积。

[Objective]In this study,the effects of different external nitrogen forms on acidolyzable organic nitrogen fractions (AON) in tobacco-planting soil were evaluated,which provides a theoretical basis for soil conservation and targeted fertilization in tobacco-growing region.[Methods]A ^(15)N tracing incubation experiment of Enshi tobacco-growing soil was carried out to analyze the N transformation of external nitrogen forms (i.e.,ammonia N,nitrate N and amino acid N) in AON as well as it’s fractions,including ammonium nitrogen (AN),amino acid nitrogen (AAN),amino sugar nitrogen (ASN) and unknown acidolyzable nitrogen (UAN).[Results](1) At 0-10 d,50-70 % ammonia ^(15)N was transformed into AON,while the conversion rate (R) of amino acid ^(15)N was slightly lower (45-55 %),and that of nitrate ^(15)N was only 27-31%.However,there was no difference in R values among the treatments,which were about 30%.(2) The weighted averages ^(15)N of ammonia,nitrate and amino acid in AON were 9.84 mg/kg,8.40 mg/kg and 10.49 mg/kg,respectively,indicating insignificant difference.However,the weighted average ^(14)N in AON was significant different among treatments,the one of ammonia N was-116.71 mg/kg,while the one of the nitrate N and amino acid N were 28.05 mg/kg and 69.84 mg/kg,respectively.(3) Based on the path analysis of structural equation model,it was found that the AN-ASN and ASN-UAN pathways of ammonia N were enhanced,and r values were both positive,indicating that ASN accelerated the transformation from AN into UAN.However,the r values of AN-AAN、ANN-UAN of amino acid N were negative,and ANN inhibited the transformation from AN to UAN.(4) At 1 d,AON of ammonia N was slightly higher than that of other treatments,but then it decreased rapidly and became significantly lower than that of nitrate N and amino acid N at 30 d.[Conclusion]There was no difference in the transformation of ^(15)N of different external nitrogen forms,but it had a greater impact on the transformation of ^(14)N.Amino acid N and nitrate N could increase the AON by increasing the ^(14)N input from other sources,while ammonia N was not conducive to the accumulation of AON by increasing the ^(14)N output.